Chrysler Full-Size Trucks 1967-1988 Repair Guide

Carbureted Engines

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ALL 1967 MODELS



Without Cleaner Air Package (CAP)

1967 CAP carburetors can be identified by a green tag on the air horn.

  1. Remove the air cleaner.
  2.  
  3. Run the engine at fast idle to stabilize the engine temperature.
  4.  
  5. Make sure that the choke plate is fully released.
  6.  
  7. Connect a tachometer to the engine following the manufacturer's instructions.
  8.  
  9. On models with 6-cylinder engines, turn the high beam headlights on. If equipped with air conditioning, turn the air conditioner on. The transmission should be in Neutral (manual) or Park (automatic).
  10.  
  11. Adjust the carburetor idle speed screw to obtain the specified idle speed.
  12.  
  13. Turn the idle mixture screws in or out to obtain the highest possible rpm. After obtaining the highest rpm, turn each mixture screw clockwise until the rpm start to drop. Then, turn the screws counterclockwise just enough to regain the lost rpm.
  14.  
  15. If the idle mixture adjustment has changed the idle speed, readjust the idle speed.
  16.  
  17. Remove the tachometer and install the air cleaner.
  18.  
  19. Remember to turn the lights off when you're finished.
  20.  

ALL 1967-76 MODELS AND 1977 CALIFORNIA MODELS



With Cleaner Air Package (CAP) or Cleaner Air System (CAS)

See Figure 1

CAS replaced CAP in the 1318 model year. CAP carburetors are identified by a green tag attached to the carburetor air horn.

To adjust the idle speed and mixture on these carburetors, particularly on later models, it is best to use an exhaust gas analyzer. This will insure that the proper level of emissions is maintained. However, if you do not have an exhaust gas analyzer, use the following procedure and eliminate those steps which pertain to the exhaust gas analyzer. When you have adjusted the carburetor, it would be wise to have it checked with an exhaust gas analyzer.

  1. Leave the air cleaner installed.
  2.  
  3. Run the engine at fast idle speed to stabilize the engine temperature.
  4.  
  5. Make sure the choke plate is fully released.
  6.  
  7. Connect a tachometer to the engine, following the manufacturer's instructions.
  8.  
  9. Connect an exhaust gas analyzer and insert the probe as far into the tailpipe as possible. On vehicles with dual exhaust, insert the probe into the left side pipe, since this is the side with the heat riser.
  10.  
  11. Check the ignition timing, and set it to specification if necessary.
  12.  
  13. If equipped with air conditioning, turn the air conditioner off. On 6-cylinder engines, turn the high beam headlights on.
  14.  
  15. Put the transmission in Neutral (manual) or Park (automatic). Make sure the hot idle compensator valve is fully seated.
  16.  
  17. If equipped with a distributor vacuum control valve, place a clamp on the line between the valve and the intake manifold.
  18.  
  19. Turn the engine idle speed adjusting screw in or out to adjust the idle speed to specification. If the carburetor is equipped with an electric solenoid throttle positioner, turn the solenoid adjusting screw in or out to obtain the specified rpm.
  20.  



Click image to see an enlarged view

Fig. Fig. 1: Throttle positioner system

  1. Adjust the curb idle speed screw until it just touches the stop on the carburetor body. Back the curb idle speed screw out 1 full turn.
  2.  
  3. Turn each idle mixture adjustment screw 1 / 16 turn richer (counterclockwise). Wait 10 seconds and observe the reading on the exhaust gas analyzer. Continue this procedure until the meter indicates a definite increase in richness of the mixture.
  4.  

This step is very important when using an exhaust gas analyzer. A carburetor that is set too lean will cause a false reading from the analyzer, indicating a rich mixture. Because of this, the carburetor must first be known to have a rich mixture to verify the reading on the analyzer.

  1. After verifying the reading on the meter, adjust the mixture screws to obtain an air/fuel ratio of 14.2:1. Turn the mixture screws clockwise (leaner) to raise the meter reading or counterclockwise (richer) to lower the meter reading.
  2.  

On 1975-77 models, adjust to get the air/fuel ratio and percentage of CO indicated on the engine compartment sticker.

  1. If the idle speed changes as the mixture screws are adjusted, adjust the speed to specification (see Step 10), then readjust the mixture so that the specified air/fuel ratio is maintained at the specified idle speed. If the idle is rough, the screws may be adjusted independently, provided that the 14.2:1 air/fuel ratio is maintained.
  2.  
  3. Remove the analyzer, the tachometer and the clamp on the vacuum line.
  4.  

HOLLEY 6145 CARBURETOR



See Figures 2 and 3



Click image to see an enlarged view

Fig. Fig. 2: 1983-85 Holley 6145 electronic feedback carburetor



Click image to see an enlarged view

Fig. Fig. 3: 1986-87 Holley 6145 electronic feedback carburetor

Idle Set RPM Adjustment
1977 AND LATER MODELS
  1. Disconnect and plug vacuum hose at the EGR valve and ground the carburetor switch with a jumper wire.
  2.  
  3. Disconnect and plug the 3 / 16 in. diameter hose at the canister.
  4.  
  5. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  6.  
  7. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  8.  
  9. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  10.  
  11. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  12.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  
  5. Reconnect O 2 sensor wire, hose to computer, PCV valve and canister hose.
  6.  
  7. Remove ground wire from carburetor switch and reconnect hose to EGR valve.
  8.  

The idle speed with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST.

  1. Turn the engine OFF and remove the tachometer.
  2.  

Solenoid Idle Stop (SIS) RPM Adjustment
1977 AND LATER MODELS

This adjustment may not apply to all vehicles.

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug the 3 / 16 in. diameter hose at the canister and remove the PCV valve from the valve cover and allow it to draw underhood air.
  6.  
  7. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  8.  
  9. Energize the solenoid by one of the following methods:
    1. Without air conditioning: Connect one end of a jumper wire to the solenoid wire and the other end to the battery positive post.
    2.  

  10.  

Use care in jumping to the correct wire on the solenoid. Applying battery voltage to the wrong wire will damage the wiring harness.

    1. With air conditioning: Press the air conditioning button on, set blower speed to low and disconnect the air conditioning compressor clutch wire.
    2.  

  1. Open throttle slightly to allow the solenoid plunger to extend.
  2.  
  3. Remove the adjusting screw and spring from the solenoid. Insert a 1 / 8 in. Allen wrench into the solenoid and turn to adjust to the specified S.I.S. rpm.
  4.  
  5. Reinstall solenoid screw and spring and de-energize solenoid.
  6.  
  7. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  8.  
  9. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  10.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  
  5. Reconnect the O 2 sensor wire, hose the computer, PCV valve and canister hose.
  6.  
  7. Remove ground wire from carburetor switch and reconnect hose to EGR valve.
  8.  

The idle rpm with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST.

  1. Turn the engine OFF and remove the tachometer.
  2.  

Propane Assisted Idle Mixture Adjustment

1977 AND LATER MODELS

This procedure should only be used if an idle defect still exists after normal diagnosis has revealed no other faulty condition, such as incorrect idle speed, incorrect basic timing, faulty hose or wire connections, etc. It is also important to make sure the combustion computer systems are operating properly. Adjustment of the air-fuel mixture should also be performed after a major carburetor overhaul.

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  
  9. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  10.  
  11. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  12.  
  13. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  14.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Disconnect the vacuum hose from the heated air door sensor at the carburetor and install the propane supply in its place.
  4.  
  5. Open the propane main valve. Slowly open the propane metering valve until maximum engine rpm is reached.
  6.  

When too much propane is added, engine speed will decrease. Fine tune the metering valve for the highest engine rpm. Also, if the idle mixture is extremely rich, engine rpm will decrease with any amount of propane. In this case, turn the idle mixture screw in about1/2turn and repeat Step 10.

  1. With the propane still flowing, adjust the idle speeds screw on the solenoid until the tachometer indicates the specified propane rpm.
  2.  
  3. Fine tune the metering valve for the highest engine rpm. If there has been a change in the maximum rpm, readjust the idle speed screw to the specified propane rpm.
  4.  
  5. Turn off the main propane valve and allow the engine speed to stabilize.
  6.  
  7. Remove the concealment plug as follows:
    1. Remove the air cleaner.
    2.  
    3. Disconnect all hoses from front of the carburetor base.
    4.  
    5. Center punch at a point 1 / 4 in. (6mm) from the end of the mixture screw housing. The center punch mark should be indexed at about the 2 o'clock position.
    6.  
    7. Drill through the outer housing at the punch mark with a 3 / 16 in. drill bit.
    8.  
    9. If the concealment plug does not pop out when the drill bit enters the plug cavity, use a small drift, punch or Allen wrench to pry out plug. Save concealment plug for reinstallation.
    10.  

  8.  

Never place any tool against the mixture screw during this operation.

  1. Slowly adjust the mixture screw until the tachometer indicates the specified idle rpm. Pause between adjustments to allow the engine speed to stabilize.
  2.  
  3. Turn on the propane valve.
  4.  
  5. Fine tune the metering valve to get the highest engine rpm. If the maximum speed is more than 25 rpm different from the specified propane rpm, repeat Steps 10-13 and 15-16. If okay, proceed to Step 18.
  6.  
  7. Turn off both valves on the propane bottle.
  8.  
  9. Remove propane supply hose and reinstall the vacuum hose that goes to the heated air door sensor.
  10.  
  11. Remove the jumper wire from the carburetor ground switch.
  12.  
  13. Reinstall the PCV valve, remove the jumper wire and reconnect radiator fan plug and reconnect O 2 system test connector.
  14.  
  15. Unplug and reconnect the vacuum hose connector to the EGR valve.
  16.  

After Steps 18-21 are completed, the curb idle speed may be different than the idle set rpm. This is normal and engine speed should not be readjusted.

  1. Turn the engine OFF and remove tachometer. Reinstall the concealment plug.
  2.  
  3. Reinstall hoses and air cleaner.
  4.  

HOLLEY 2280/6280 CARBURETOR



See Figures 4 through 9



Click image to see an enlarged view

Fig. Fig. 4: 1980 Holley 2280 carburetor



Click image to see an enlarged view

Fig. Fig. 5: 1981 Holley 2280 carburetor



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Fig. Fig. 6: 1982-83 Holley 2280 carburetor



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Fig. Fig. 7: 1984-86 Holley 2280/6280 carburetor



Click image to see an enlarged view

Fig. Fig. 8: 1987 Holley 2280 carburetor



Click image to see an enlarged view

Fig. Fig. 9: 1987 Holley 6280 carburetor

Idle RPM Adjustment

See Figure 10

  1. Turn off all lights and accessories.
  2.  
  3. Place the transmission in Neutral (manual) or Park (automatic) and set the parking brake.
  4.  
  5. Start engine and run until operating temperature is reached.
  6.  
  7. Ground the carburetor switch with a jumper wire.
  8.  
  9. Disconnect and plug computer, EGR valve and 3 / 16 in. diameter canister vacuum hoses.
  10.  
  11. Remove PCV valve from the valve cover and allow it to draw underhood air.
  12.  
  13. Disconnect wire from the O 2 sensor and ground it with a jumper wire. Let the engine run for 4 minutes before proceeding.
  14.  
  15. Connect a tachometer to engine.
  16.  
  17. Turn the screw on the solenoid and adjust engine speed to the idle rpm, as specified on the Emission Label.
  18.  



Click image to see an enlarged view

Fig. Fig. 10: Idle adjusting screw location on the Holley 2280 carburetor

  1. Remove jumper wire from O 2 sensor harness connector and reconnect to O 2 sensor.
  2.  
  3. Reinstall PCV into valve cover.
  4.  
  5. Reconnect all vacuum hoses.
  6.  
  7. Remove jumper wire from carburetor switch.
  8.  

The idle speed with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST.

  1. Turn the engine OFF and remove the tachometer.
  2.  

Solenoid Idle Stop (SIS) RPM Adjustment
  1. Turn off all lights and accessories, place the transmission in Neutral (manual) or Park (automatic) and set the parking brake.
  2.  
  3. Start and run the engine until operating temperature is reached.
  4.  
  5. Ground the carburetor switch with a jumper wire.
  6.  
  7. Disconnect and plug the EGR valve and 3 / 16 in. diameter canister vacuum hoses.
  8.  
  9. Remove PCV valve from the valve cover and allow to draw underhood air.
  10.  
  11. Connect a tachometer to engine.
  12.  
  13. Energize the solenoid by one of the following methods:
    1. Without air conditioning: Connect one end of a jumper wire to the solenoid wire and the other end to the battery positive post.
    2.  

  14.  

Use care in jumping to the correct wire on the solenoid. Applying battery voltage to the wrong wire will damage the wiring harness.

    1. With air conditioning: Press the air conditioning button on, set blower speed to low and disconnect the air conditioning compressor clutch wire.
    2.  

  1. Open throttle slightly to allow the solenoid plunger to extend.
  2.  
  3. Remove the adjusting screw and spring from the solenoid. Insert a 1 / 8 in. Allen wrench into the solenoid and turn to adjust to specified SIS rpm.
  4.  
  5. Reinstall solenoid screw and spring until it lightly bottoms out and de-energize solenoid.
  6.  
  7. Remove and plug the vacuum hose from the computer.
  8.  
  9. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  10.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  
  5. Reconnect the O 2 sensor wire, hose the computer, PCV valve and canister hose.
  6.  
  7. Remove ground wire from carburetor switch and reconnect hose to EGR valve. The idle rpm with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST.
  8.  
  9. Turn the engine OFF and remove the tachometer.
  10.  

Propane Assisted Idle Mixture Adjustment

See Figure 11

This procedure should only be used if an idle defect still exists after normal diagnosis has revealed no other faulty condition, such as incorrect idle speed, incorrect basic timing, faulty hose or wire connections, etc. It is also important to make sure the combustion computer systems are operating properly. Adjustment of the air-fuel mixture should also be performed after a major carburetor overhaul.

  1. Turn off all lights and accessories.
  2.  
  3. Place transmission in Neutral (manual) or Park (automatic) and set the parking brake.
  4.  
  5. Start the engine and run until operating temperature is reached.
  6.  
  7. Ground the carburetor switch with a jumper wire.
  8.  
  9. Disconnect and plug computer, EGR valve and 3 / 16 in. diameter canister vacuum hoses.
  10.  
  11. Remove PCV valve from the valve cover and allow it to draw underhood air.
  12.  
  13. Disconnect wire from the O 2 sensor and ground it with a jumper wire. Let the engine run for 4 minutes before proceeding.
  14.  
  15. Connect a tachometer to engine.
  16.  
  17. Tee in propane supply hose in the vacuum line to the choke vacuum kick diaphragm.
  18.  
  19. Open the propane main valve. Slowly open the propane metering valve until maximum engine rpm is reached.
  20.  
  21. If your truck still has the concealment plugs proceed as follows:
    1. Remove the air cleaner and disconnect all hoses from front of the carburetor base.
    2.  
    3. Remove the carburetor from the engine.
    4.  
    5. Remove the throttle body and place in a vise, with gasket surfaces not touching the jaws of the vise.
    6.  
    7. Drill a 5 / 64 in. (2mm) pilot hole at a 45° angle into the casting towards the concealment plugs.
    8.  
    9. Redrill the hole to 1 / 8 in. (3mm). Repeat this procedure on the opposite side, as illustrated.
    10.  
    11. Insert a blunt punch into the holes and drive out the plugs.
    12.  
    13. Reassemble and reinstall carburetor on engine.
    14.  
    15. Reinstall hoses and air cleaner.
    16.  

  22.  



Click image to see an enlarged view

Fig. Fig. 11: Concealment plug removal on the Holley 2280 carburetor

When too much propane is added, engine speed will decrease. Fine tune the metering valve for the highest engine rpm. Also, if the idle mixture is extremely rich, engine rpm will decrease with any amount of propane. In this case, turn the idle mixture screw in about1/2turn and repeat Step 12.

  1. With the propane still flowing, adjust the idle speeds screw on the solenoid until the tachometer indicates the specified propane rpm.
  2.  
  3. Fine tune the metering valve for the highest engine rpm. If there has been a change in the maximum rpm, readjust the idle speed screw to the specified propane rpm.
  4.  
  5. Turn off the main propane valve and allow the engine speed to stabilize.
  6.  
  7. Slowly adjust the mixture screw(s) until the tachometer indicates the specified idle rpm. Pause between adjustments to allow the engine speed to stabilize.
  8.  
  9. Turn on the propane valve.
  10.  
  11. Fine tune the metering valve to get the highest engine rpm. If the maximum speed is more than 25 rpm different from the specified propane rpm, repeat Steps 12 and 14-18. If okay, proceed to Step 20.
  12.  
  13. Turn off both valves on the propane bottle.
  14.  
  15. Remove propane supply hose.
  16.  
  17. Remove the jumper wire from the carburetor ground switch.
  18.  
  19. Reinstall the PCV valve, remove the jumper wire from O 2 sensor harness connector and reconnect O 2 sensor connector.
  20.  
  21. Unplug and reconnect the vacuum hose connector to the computer, canister and EGR valve.
  22.  

After Steps 20-24 are completed, the curb idle speed may be different than the idle set rpm. This is normal and engine speed should not be readjusted.

  1. Turn the engine OFF and remove the tachometer. Reinstall the concealment plug.
  2.  

CARTER BBD CARBURETOR



See Figures 12 through 16



Click image to see an enlarged view

Fig. Fig. 12: 1980-81 Carter BBD carburetor



Click image to see an enlarged view

Fig. Fig. 13: 1982 Carter BBD carburetor



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Fig. Fig. 14: 1983 Carter BBD carburetor



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Fig. Fig. 15: 1984-87 Carter BBD non-feedback carburetor



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Fig. Fig. 16: 1984-87 Carter BBD feedback carburetor

Idle RPM Adjustment

See Figure 17

  1. Disconnect and plug vacuum hose at the EGR valve and ground the carburetor switch with a jumper wire.
  2.  
  3. Disconnect and plug the 3 / 16 in. diameter hose at the canister.
  4.  
  5. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  6.  
  7. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  8.  
  9. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  10.  
  11. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  12.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  



Click image to see an enlarged view

Fig. Fig. 17: Idle adjustment screw location on the Carter BBD carburetor

  1. Reconnect O 2 sensor wire, hose to computer, PCV valve and canister hose.
  2.  
  3. Remove ground wire from carburetor switch and reconnect hose to EGR valve.
  4.  
  5. The idle speed with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST. Turn the engine OFF and remove the tachometer.
  6.  

Solenoid Idle Stop (SIS) RPM Adjustment
  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug the 3 / 16 in. diameter hose at the canister and remove the PCV valve from the valve cover and allow it to draw underhood air.
  6.  
  7. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  8.  
  9. Energize the solenoid by one of the following methods:
    1. Without air conditioning: Connect one end of a jumper wire to the solenoid wire and the other end to the battery positive post.
    2.  

  10.  

Use care in jumping to the correct wire on the solenoid. Applying battery voltage to the wrong wire will damage the wiring harness.

    1. With air conditioning: Press the air conditioning button ON, set blower speed to low and disconnect the air conditioning compressor clutch wire.
    2.  

  1. Open throttle slightly to allow the solenoid plunger to extend.
  2.  
  3. Turn the screw on the throttle lever to adjust to specified SIS rpm.
  4.  
  5. De-energize solenoid.
  6.  
  7. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  8.  
  9. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  10.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  
  5. Reconnect the O 2 sensor wire, hose the computer, PCV valve and canister hose.
  6.  
  7. Remove ground wire from carburetor switch and reconnect hose to EGR valve.
  8.  
  9. The idle rpm with the engine in its normal operating mode (everything connected) may vary from set speeds. DO NOT READJUST. Turn the engine OFF and remove the tachometer.
  10.  

Propane Assisted Idle Mixture Adjustment

See Figure 18

This procedure should only be used if an idle defect still exists after normal diagnosis has revealed no other faulty condition, such as incorrect idle speed, incorrect basic timing, faulty hose or wire connections, etc. It is also important to make sure the combustion computer systems are operating properly. Adjustment of the air-fuel mixture should also be performed after a major carburetor overhaul.

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  
  9. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  10.  
  11. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  12.  
  13. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  14.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Disconnect the vacuum hose from the heated air door sensor at the carburetor and install the propane supply in its place.
  4.  
  5. Open the propane main valve. Slowly open the propane metering valve until maximum engine rpm is reached.
  6.  

When too much propane is added, engine speed will decrease. Fine tune the metering valve for the highest engine rpm. Also, if the idle mixture is extremely rich, engine rpm will decrease with any amount of propane. In this case, turn the idle mixture screw in about1/2turn and repeat Step 10.

  1. With the propane still flowing, adjust the idle speeds screw on the solenoid until the tachometer indicates the specified propane rpm.
  2.  
  3. Fine tune the metering valve for the highest engine rpm. If there has been a change in the maximum rpm, readjust the idle speed screw to the specified propane rpm.
  4.  
  5. Turn off the main propane valve and allow the engine speed to stabilize.
  6.  
  7. If your truck has not had the concealment plug removed, proceed as follows:
    1. Remove the air cleaner and disconnect all hoses from front of the carburetor base.
    2.  
    3. Remove the carburetor from the engine.
    4.  
    5. Remove the throttle body and place in a vise, with gasket surfaces not touching the jaws of the vise.
    6.  
    7. Drill a 5 / 64 in. (2mm) pilot hole at a 45° angle into the casting towards the concealment plugs.
    8.  
    9. Redrill the hole to 1 / 8 in. (3mm). Repeat this procedure on the opposite side, as illustrated.
    10.  
    11. Insert a blunt punch into the holes and drive out the plugs.
    12.  
    13. Reassemble, then reinstall the carburetor on the engine.
    14.  

  8.  



Click image to see an enlarged view

Fig. Fig. 18: Concealment plug removal on the Carter BBD carburetor

  1. Reinstall hoses and air cleaner.
  2.  
  3. Slowly adjust the mixture screw until the tachometer indicates the specified idle rpm. Pause between adjustments to allow the engine speed to stabilize.
  4.  
  5. Turn on the propane valve.
  6.  
  7. Fine tune the metering valve to get the highest engine rpm. If the maximum speed is more than 25 rpm different from the specified propane rpm, repeat Steps 10-13 and 14-15. If okay, proceed to Step 19.
  8.  
  9. Turn off both valves on the propane bottle.
  10.  
  11. Remove propane supply hose and reinstall the vacuum hose that goes to the heated air door sensor.
  12.  
  13. Remove the jumper wire from the carburetor ground switch.
  14.  
  15. Reinstall the PCV valve, remove the jumper wire and reconnect radiator fan plug and reconnect O 2 system test connector.
  16.  
  17. Unplug and reconnect the vacuum hose connector to the EGR valve.
  18.  
  19. After Steps 19-23 are completed, the curb idle speed may be different than the idle set rpm. This is normal and engine speed should not be readjusted. Turn the engine OFF and remove the tachometer. Reinstall the concealment plug.
  20.  

CARTER THERMO-QUAD CARBURETOR



See Figures 19 through 23



Click image to see an enlarged view

Fig. Fig. 19: 1979 Thermo-Quad carburetor



Click image to see an enlarged view

Fig. Fig. 20: 1980-81 Thermo-Quad carburetor



Click image to see an enlarged view

Fig. Fig. 21: 1982 Thermo-Quad carburetor



Click image to see an enlarged view

Fig. Fig. 22: 1983 Thermo-Quad carburetor



Click image to see an enlarged view

Fig. Fig. 23: 1984 Thermo-Quad carburetor

Idle RPM Adjustment
  1. Disconnect and plug vacuum hose at the EGR valve and ground the carburetor switch with a jumper wire.
  2.  
  3. Disconnect and plug the 3 / 16 in. diameter hose at the canister.
  4.  
  5. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  6.  
  7. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  8.  
  9. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  10.  
  11. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  12.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  
  5. Reconnect O 2 sensor wire, hose to computer, PCV valve and canister hose.
  6.  
  7. Remove ground wire from carburetor switch and reconnect hose to EGR valve.
  8.  
  9. The idle speed with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST. Turn the engine OFF and remove the tachometer.
  10.  

Solenoid Idle Stop (SIS) RPM Adjustment
  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug the 3 / 16 in. diameter hose at the canister and remove the PCV valve from the valve cover and allow it to draw underhood air.
  6.  
  7. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  8.  
  9. Energize the solenoid by one of the following methods:
    1. Without air conditioning: Connect one end of a jumper wire to the solenoid wire and the other end to the battery positive post.
    2.  

  10.  

Use care in jumping to the correct wire on the solenoid. Applying battery voltage to the wrong wire will damage the wiring harness.

    1. With air conditioning: Press the air conditioning button on, set blower speed to low and disconnect the air conditioning compressor clutch wire.
    2.  

  1. Open throttle slightly to allow the solenoid plunger to extend.
  2.  
  3. Turn the screw on the throttle lever to adjust to specified SIS rpm.
  4.  
  5. De-energize the solenoid.
  6.  
  7. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  8.  
  9. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  10.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  
  5. Reconnect the O 2 sensor wire, hose the computer, PCV valve and canister hose.
  6.  
  7. Remove ground wire from carburetor switch and reconnect hose to EGR valve.
  8.  
  9. The idle rpm with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST. Turn the engine OFF and remove the tachometer.
  10.  

Propane Assisted Idle Mixture

See Figure 24

This procedure should only be used if an idle defect still exists after normal diagnosis has revealed no other faulty condition, such as incorrect idle speed, incorrect basic timing, faulty hose or wire connections, etc. It is also important to make sure the combustion computer systems are operating properly. Adjustment of the air-fuel mixture should also be performed after a major carburetor overhaul.

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  
  9. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  10.  
  11. Remove and plug the vacuum hose from the computer. Connect an auxiliary vacuum supply to the computer and apply 16 in. Hg (54 kPa).
  12.  
  13. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  14.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Disconnect the vacuum hose from the heated air door sensor at the carburetor and install the propane supply in its place.
  4.  
  5. Open the propane main valve. Slowly open the propane metering valve until maximum engine rpm is reached.
  6.  

When too much propane is added, engine speed will decrease. Fine tune the metering valve for the highest engine rpm. Also, if the idle mixture is extremely rich, engine rpm will decrease with any amount of propane. In this case, turn the idle mixture screw in about1/2turn and repeat Step 10.

  1. With the propane still flowing, adjust the idle speeds screw on the solenoid until the tachometer indicates the specified propane rpm.
  2.  
  3. Fine tune the metering valve for the highest engine rpm. If there has been a change in the maximum rpm, readjust the idle speed screw to the specified propane rpm.
  4.  
  5. Turn off the main propane valve and allow the engine speed to stabilize.
  6.  
  7. If your truck has not had the concealment plug removed, proceed as follows:
    1. Remove the air cleaner and disconnect all hoses from front of the carburetor base.
    2.  
    3. Remove the carburetor from engine.
    4.  
    5. Remove the throttle body and place in a vise, with gasket surfaces not touching the jaws of the vise.
    6.  
    7. Drill a 5 / 64 in. (2mm) pilot hole at a 45° angle into the casting towards the concealment plugs.
    8.  
    9. Redrill the hole to 1 / 8 in. (3mm). Repeat this procedure on the opposite side, as illustrated.
    10.  
    11. Insert a blunt punch into the holes and drive out the plugs.
    12.  

  8.  
  9. Reassemble, then reinstall the carburetor on the engine.
  10.  
  11. Reinstall hoses and air cleaner.
  12.  



Click image to see an enlarged view

Fig. Fig. 24: Concealment plug removal on the Carter Thermo-Quad carburetor

  1. Slowly adjust the mixture screw until the tachometer indicates the specified idle rpm. Pause between adjustments to allow the engine speed to stabilize.
  2.  
  3. Turn on the propane valve.
  4.  
  5. Fine tune the metering valve to get the highest engine rpm. If the maximum speed is more than 25 rpm different from the specified propane rpm, repeat Steps 10-13 and 15-18. If okay, proceed to Step 20.
  6.  
  7. Turn off both valves on the propane bottle.
  8.  
  9. Remove propane supply hose and reinstall the vacuum hose that goes to the heated air door sensor.
  10.  
  11. Remove the jumper wire from the carburetor ground switch.
  12.  
  13. Reinstall the PCV valve, remove the jumper wire and reconnect radiator fan plug and reconnect O 2 system test connector.
  14.  
  15. Unplug and reconnect the vacuum hose connector to the EGR valve.
  16.  
  17. After Steps 20-24 are completed, the curb idle speed may be different than the idle set rpm. This is normal and engine speed should not be readjusted. Turn the engine OFF and remove the tachometer. Reinstall the concealment plug.
  18.  

ROCHESTER QUADRAJET CARBURETOR



See Figure 25



Click image to see an enlarged view

Fig. Fig. 25: 1985-88 Rochester Quadrajet carburetor

Idle RPM Adjustment

See Figures 26 and 27

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug the 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  



Click image to see an enlarged view

Fig. Fig. 26: Idle system on the Rochester Quadrajet carburetor

  1. Connect a tachometer to the engine.
  2.  
  3. Start the engine and let the speed stabilize for two minutes.
  4.  
  5. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  6.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for four minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  
  5. Reconnect O 2 sensor wire.
  6.  
  7. Reinstall PCV valve.
  8.  
  9. Reconnect canister hose.
  10.  
  11. Remove ground wire from carburetor switch.
  12.  
  13. Reconnect hose to EGR valve.
  14.  
  15. The idle speed with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST. Turn the engine OFF and remove the tachometer.
  16.  

Solenoid Idle Stop (SIS) RPM Adjustment
  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug the 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  
  9. Connect a tachometer to the engine.
  10.  
  11. Start the engine and let the speed stabilize for two minutes.
  12.  
  13. Energize the solenoid by one of the following methods:
    1. Without air conditioning: Connect one end of a jumper wire to the solenoid wire and the other end to the battery positive post.
    2.  

  14.  

Use care in jumping to the correct wire on the solenoid. Applying battery voltage to the wrong wire will damage the wiring harness.

    1. With air conditioning: Press the air conditioning button on, set blower speed to low and disconnect the air conditioning compressor clutch wire.
    2.  

  1. Open throttle slightly to allow the solenoid plunger to extend.
  2.  
  3. Remove the adjusting screw and spring from the solenoid. Insert a 1 / 8 in. Allen wrench into the solenoid and turn to adjust to specified SIS rpm.
  4.  
  5. Reinstall solenoid screw and spring until it lightly bottoms out. De-energize solenoid.
  6.  
  7. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  8.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Turn the screw on the solenoid and adjust to the idle rpm, as specified on the Emission Label.
  4.  
  5. Reconnect the O 2 sensor wire, hose the computer, PCV valve and canister hose.
  6.  
  7. Remove ground wire from carburetor switch and reconnect hose to EGR valve.
  8.  

The idle rpm with the engine in normal operating condition (everything connected) may vary from set speeds. DO NOT READJUST.

  1. Turn the engine OFF and remove the tachometer.
  2.  

Propane Idle Mixture Adjustment

This procedure should only be used if an idle defect still exists after normal diagnosis has revealed no other faulty condition, such as incorrect idle speed, incorrect basic timing, faulty hose or wire connections, etc. It is also important to make sure the combustion computer systems are operating properly. Adjustment of the air/fuel mixture should also be performed after a major carburetor overhaul.

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  
  9. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  10.  
  11. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  12.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Disconnect the vacuum hose from the heated air door sensor at the carburetor and install the propane supply in its place.
  4.  
  5. Open the propane main valve. Slowly open the propane metering valve until maximum engine rpm is reached.
  6.  

When too much propane is added, engine speed will decrease. Fine tune the metering valve for the highest engine rpm. Also, if the idle mixture is extremely rich, engine rpm will decrease with any amount of propane. In this case, turn the idle mixture screw in about1/2turn and repeat Step 9.

  1. If your concealment plug has not been removed proceed as follows:
    1. Invert the carburetor and use a hacksaw to make two parallel cuts in the throttle body. Make cuts on each side of the locator points beneath the concealment plug. The cuts should reach down to the plug but should not extend more than 1 / 8 in. (3mm) beyond the locator points. The distance between the saw cuts will depend on the size of the punch to be used.
    2.  
    3. Place a flat punch at a point near the ends of the saw marks in the throttle body. Hold the punch at a 45° angle and drive it into the throttle body until the casting breaks away, exposing the steel plug.
    4.  
    5. Repeat the procedure for the other concealment plug.
    6.  
    7. Use Tool C-4205 (BT-7610B) or equivalent, to remove idle mixture screws.
    8.  

  2.  



Click image to see an enlarged view

Fig. Fig. 27: Concealment plug removal on the Rochester Quadrajet carburetor

  1. With the propane still flowing, adjust the idle speeds screw on the solenoid until the tachometer indicates the specified propane rpm.
  2.  
  3. Fine tune the metering valve for the highest engine rpm. If there has been a change in the maximum rpm, readjust the idle speed screw to the specified propane rpm.
  4.  
  5. Turn off the main propane valve and allow the engine speed to stabilize.
  6.  
  7. Slowly adjust the mixture screw until the tachometer indicates the specified idle rpm. Pause between adjustments to allow the engine speed to stabilize.
  8.  
  9. Turn on the propane valve.
  10.  
  11. Fine tune the metering valve to get the highest engine rpm. If the maximum speed is more than 25 rpm different from the specified propane rpm, repeat Steps 9 and 11-15. If okay, proceed to Step 17.
  12.  
  13. Turn off both valves on the propane bottle.
  14.  
  15. Remove propane supply hose and reinstall the vacuum hose that goes to the heated air door sensor.
  16.  
  17. Remove the jumper wire from the carburetor ground switch.
  18.  
  19. Reinstall the PCV valve, remove the jumper wire and reconnect radiator fan plug and reconnect O 2 system test connector.
  20.  
  21. Unplug and reconnect the vacuum hose connector to the EGR valve.
  22.  
  23. After Steps 17-21 are completed, the curb idle speed may be different than the idle set rpm. This is normal and engine speed should not be readjusted. Turn the engine OFF and remove the tachometer. Reinstall the concealment plug.
  24.  

HOLLEY 2210 CARBURETOR



Idle RPM Adjustment
  1. Check and adjust the timing.
  2.  
  3. Disconnect the vacuum hose at the EGR valve.
  4.  
  5. Disconnect and plug the 3 / 16 in. hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover.
  8.  
  9. Connect a tachometer.
  10.  
  11. Start the engine and run it to normal operating temperature.
  12.  
  13. Turn the idle speed control screw to adjust the engine rpm.
  14.  

Propane Idle Mixture Adjustment

This procedure should only be used if an idle defect still exists after normal diagnosis has revealed no other faulty condition, such as incorrect idle speed, incorrect basic timing, faulty hose or wire connections, etc. It is also important to make sure the combustion computer systems are operating properly. Adjustment of the air/fuel mixture should also be performed after a major carburetor overhaul.

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  
  9. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  10.  
  11. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  12.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Disconnect the vacuum hose from the heated air door sensor at the carburetor and install the propane supply in its place.
  4.  
  5. Open the propane main valve. Slowly open the propane metering valve until maximum engine rpm is reached.
  6.  

When too much propane is added, engine speed will decrease. Fine tune the metering valve for the highest engine rpm. Also, if the idle mixture is extremely rich, engine rpm will decrease with any amount of propane. In this case, turn the idle mixture screw in about1/2turn and repeat Step 9.

  1. With the propane still flowing, adjust the idle speeds screw on the solenoid until the tachometer indicates the specified propane rpm.
  2.  
  3. Fine tune the metering valve for the highest engine rpm. If there has been a change in the maximum rpm, readjust the idle speed screw to the specified propane rpm.
  4.  
  5. Turn off the main propane valve and allow the engine speed to stabilize.
  6.  
  7. If your concealment plug has not been removed proceed as follows:
    1. Invert the carburetor and use a hacksaw to make two parallel cuts in the throttle body. Make cuts on each side of the locator points beneath the concealment plug. The cuts should reach down to the plug but should not extend more than 1 / 8 in. (3mm) beyond the locator points. The distance between the saw cuts will depend on the size of the punch to be used.
    2.  
    3. Place a flat punch at a point near the ends of the saw marks in the throttle body. Hold the punch at a 45° angle and drive it into the throttle body until the casting breaks away, exposing the steel plug.
    4.  
    5. Repeat the procedure for the other concealment plug.
    6.  
    7. Use Tool C-4205 (BT-7610B) or equivalent to remove the idle mixture screws.
    8.  

  8.  
  9. Slowly adjust the mixture screw until the tachometer indicates the specified idle rpm. Pause between adjustments to allow the engine speed to stabilize.
  10.  
  11. Turn on the propane valve.
  12.  
  13. Fine tune the metering valve to get the highest engine rpm. If the maximum speed is more than 25 rpm different than the specified propane rpm, repeat Steps 9-12 and 14-15. If okay, proceed to Step 17.
  14.  
  15. Turn off both valves on the propane bottle.
  16.  
  17. Remove propane supply hose and reinstall the vacuum hose that goes to the heated air door sensor.
  18.  
  19. Remove the jumper wire from the carburetor ground switch.
  20.  
  21. Reinstall the PCV valve. Remove the jumper wire, then attach the radiator fan plug and O 2 system test connector.
  22.  
  23. Unplug and reconnect the vacuum hose connector to the EGR valve.
  24.  
  25. After Steps 17-21 are completed, the curb idle speed may be different than the idle set rpm. This is normal and engine speed should not be readjusted. Turn the engine OFF and remove the tachometer. Reinstall the concealment plug.
  26.  

HOLLEY 2245 CARBURETOR



See Figure 28



Click image to see an enlarged view

Fig. Fig. 28: 1982-84 Holley 2245 carburetor

Idle RPM Adjustment

See Figure 29

  1. Check and adjust the timing.
  2.  
  3. Disconnect the vacuum hose at the EGR valve.
  4.  
  5. Disconnect and plug the 3 / 16 in. hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover.
  8.  
  9. Connect a tachometer.
  10.  
  11. Start the engine and run it to normal operating temperature.
  12.  
  13. Turn the idle speed control screw to adjust the engine rpm.
  14.  



Click image to see an enlarged view

Fig. Fig. 29: Idle adjustment screw location on the Holley 2245 carburetor

Propane Idle Mixture Adjustment

This procedure should only be used if an idle defect still exists after normal diagnosis has revealed no other faulty condition, such as incorrect idle speed, incorrect basic timing, faulty hose or wire connections, etc. It is also important to make sure the combustion computer systems are operating properly. Adjustment of the air/fuel mixture should also be performed after a major carburetor overhaul.

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  
  9. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  10.  
  11. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  12.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Disconnect the vacuum hose from the heated air door sensor at the carburetor and install the propane supply in its place.
  4.  
  5. Open the propane main valve. Slowly open the propane metering valve until maximum engine rpm is reached.
  6.  

When too much propane is added, engine speed will decrease. Fine tune the metering valve for the highest engine rpm. Also, if the idle mixture is extremely rich, engine rpm will decrease with any amount of propane. In this case, turn the idle mixture screw in about1/2turn and repeat Step 9.

  1. If your concealment plug has not been removed proceed as follows:
    1. Invert the carburetor and use a hacksaw to make two parallel cuts in the throttle body. Make cuts on each side of the locator points beneath the concealment plug. The cuts should reach down to the plug but should not extend more than 1 / 8 in. beyond the locator points. The distance between the saw cuts will depend on the size of the punch to be used.
    2.  
    3. Place a flat punch at a point near the ends of the saw marks in the throttle body. Hold the punch at a 45° angle and drive it into the throttle body until the casting breaks away, exposing the steel plug.
    4.  

  2.  
  3. Repeat the procedure for the other concealment plug.
  4.  
  5. Use Tool C-4205 (BT-7610B) or equivalent, to remove idle mixture screws.
  6.  
  7. With the propane still flowing, adjust the idle speeds screw on the solenoid until the tachometer indicates the specified propane rpm.
  8.  
  9. Fine tune the metering valve for the highest engine rpm. If there has been a change in the maximum rpm, readjust the idle speed screw to the specified propane rpm.
  10.  
  11. Turn off the main propane valve and allow the engine speed to stabilize.
  12.  
  13. If your concealment plug has not been removed proceed as follows:
    1. Invert the carburetor and use a hacksaw to make two parallel cuts in the throttle body. Make cuts on each side of the locator points beneath the concealment plug. The cuts should reach down to the plug but should not extend more than 1 / 8 in. beyond the locator points. The distance between the saw cuts will depend on the size of the punch to be used.
    2.  
    3. Place a flat punch at a point near the ends of the saw marks in the throttle body. Hold the punch at a 45° angle and drive it into the throttle body until the casting breaks away, exposing the steel plug.
    4.  

  14.  
  15. Slowly adjust the mixture screw until the tachometer indicates the specified idle rpm. Pause between adjustments to allow the engine speed to stabilize.
  16.  
  17. Turn on the propane valve.
  18.  
  19. Fine tune the metering valve to get the highest engine rpm. If the maximum speed is more than 25 rpm different from the specified propane rpm, repeat Steps 9-14. If okay, proceed to Step 16.
  20.  
  21. Turn off both valves on the propane bottle.
  22.  
  23. Remove propane supply hose and reinstall the vacuum hose that goes to the heated air door sensor.
  24.  
  25. Remove the jumper wire from the carburetor ground switch.
  26.  
  27. Reinstall the PCV valve, remove the jumper wire and reconnect radiator fan plug and reconnect O 2 system test connector.
  28.  
  29. Unplug and reconnect the vacuum hose connector to the EGR valve.
  30.  
  31. After Steps 16-20 are completed, the curb idle speed may be different than the idle set rpm. This is normal and engine speed should not be readjusted. Turn the engine OFF and remove the tachometer. Reinstall the concealment plug.
  32.  

HOLLEY 1945 CARBURETOR



See Figures 30 through 34



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Fig. Fig. 30: 1978 Holley 1945 carburetor



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Fig. Fig. 31: 1979-80 Holley 1945 carburetor-California



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Fig. Fig. 32: 1979-80 Holley 1945 carburetor-49 states and Canada



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Fig. Fig. 33: 1981 Holley 1945 carburetor



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Fig. Fig. 34: 982-87 Holley 1945 carburetor

Solenoid Idle Stop Adjustment

See Figure 35

  1. Check ignition timing to ensure proper idle speed.
  2.  
  3. Disconnect and plug the vacuum hose at the EGR valve.
  4.  
  5. Disconnect and plug the 3 / 16 in. diameter control hose at the canister.
  6.  



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Fig. Fig. 35: Solenoid Idle Stop location on the Holley 1945 carburetor

  1. Remove the PCV valve to allow it to draw air.
  2.  
  3. Turn on the air conditioning and set the blower on low.
  4.  
  5. Disconnect the air conditioning clutch wire.
  6.  
  7. On trucks without A/C, connect a jumper wire between the battery positive post and the SIS lead wire.
  8.  


WARNING
Make sure to use care when jumping to the proper wire on the solenoid. Applying battery voltage to other than the correct wire will damage the wiring harness.

  1. Open the throttle slightly to allow the solenoid plunger to extend.
  2.  
  3. Remove the adjusting screw and spring from the solenoid. Insert a 1 / 8 in. Allen head wrench into the solenoid and turn to set the correct idle speed.
  4.  
  5. Turn the A/C off and reconnect the clutch wire, or remove the jumper wire.
  6.  
  7. Replace the solenoid screw and spring. Proceed to the Idle RPM Adjustment.
  8.  

Idle RPM Adjustment

See Figures 36 and 37

  1. Check and adjust the timing.
  2.  
  3. Disconnect the vacuum hose at the EGR valve.
  4.  
  5. Disconnect and plug the 3 / 16 in. hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover.
  8.  



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Fig. Fig. 36: Use a screwdriver to set the idle rpm



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Fig. Fig. 37: Holly model 1945 carburetor

  1. Ground the carburetor switch with a jumper wire.
  2.  
  3. Connect a tachometer.
  4.  
  5. Start the engine and run it to normal operating temperature.
  6.  
  7. Turn the idle speed control screw on the idle solenoid to adjust the engine rpm.
  8.  

Propane Idle Mixture Adjustment

See Figure 38

This procedure should only be used if an idle defect still exists after normal diagnosis has revealed no other faulty condition, such as incorrect idle speed, incorrect basic timing, faulty hose or wire connections, etc. It is also important to make sure the combustion computer systems are operating properly. Adjustment of the air/fuel mixture should also be performed after a major carburetor overhaul.

  1. Disconnect and plug vacuum hose at the EGR valve.
  2.  
  3. Ground the carburetor switch with a jumper wire.
  4.  
  5. Disconnect and plug 3 / 16 in. diameter hose at the canister.
  6.  
  7. Remove the PCV valve from the valve cover and allow it to draw underhood air.
  8.  
  9. Connect a tachometer to the engine, then start the engine and let the speed stabilize for two minutes.
  10.  
  11. Disconnect the engine harness connector from the O 2 sensor and ground the engine harness lead with a jumper wire.
  12.  

Care should be exercised so that no pulling force is put on the wire attached to the O2sensor. The bullet connector to be disconnected is approximately 4 in. (10.2cm) from the sensor. Use care in working around the sensor, as the exhaust manifold is extremely hot.

  1. Let the engine run for 4 minutes to allow the effect of disconnecting the O 2 sensor to take place.
  2.  
  3. Disconnect the vacuum hose from the heated air door sensor at the carburetor and install the propane supply in its place.
  4.  
  5. Open the propane main valve. Slowly open the propane metering valve until maximum engine rpm is reached.
  6.  

When too much propane is added, engine speed will decrease. Fine tune the metering valve for the highest engine rpm. Also, if the idle mixture is extremely rich, engine rpm will decrease with any amount of propane. In this case, turn the idle mixture screw in about1/2turn and repeat Step 9.

  1. With the propane still flowing, adjust the idle speeds screw on the solenoid until the tachometer indicates the specified propane rpm.
  2.  
  3. Fine tune the metering valve for the highest engine rpm. If there has been a change in the maximum rpm, readjust the idle speed screw to the specified propane rpm.
  4.  
  5. Turn off the main propane valve and allow the engine speed to stabilize.
  6.  
  7. If your concealment plug has not been removed proceed as follows:
    1. Remove the carburetor from the engine.
    2.  
    3. Remove the throttle body from the carburetor.
    4.  
    5. Using a vise, clamp the carburetor, with gasket surfaces not touching the vise jaws.
    6.  
    7. Drill a 5 / 64 in. (2mm) hole in the casting around the idle mixture screw, then redrill the hole to 1 / 8 in. (3mm).
    8.  
    9. Insert a blunt punch into the hole and drive out the plug.
    10.  

  8.  
  9. Install the carburetor on the engine.
  10.  
  11. Proceed with the Propane assisted idle procedure.
  12.  



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Fig. Fig. 38: Concealment plug removal on the Holley 1945 carburetor

  1. Slowly adjust the mixture screw until the tachometer indicates the specified idle rpm. Pause between adjustments to allow the engine speed to stabilize.
  2.  
  3. Turn on the propane valve.
  4.  
  5. Fine tune the metering valve to get the highest engine rpm. If the maximum speed is more than 25 rpm different from the specified propane rpm, repeat Steps 9-12 and 14-17. If okay, proceed to Step 19.
  6.  
  7. Turn off both valves on the propane bottle.
  8.  
  9. Remove propane supply hose and reinstall the vacuum hose that goes to the heated air door sensor.
  10.  
  11. Remove the jumper wire from the carburetor ground switch.
  12.  
  13. Reinstall the PCV valve, remove the jumper wire and reconnect radiator fan plug and reconnect O 2 system test connector.
  14.  
  15. Unplug and reconnect the vacuum hose connector to the EGR valve.
  16.  
  17. After Steps 17-23 are completed, the curb idle speed may be different than the idle set rpm. This is normal and engine speed should not be readjusted. Turn the engine OFF and remove the tachometer. Reinstall the concealment plug.
  18.  

 
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