GM Astro/Safari 1985-1996 Repair Guide

Carburetor

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ADJUSTMENTS



Idle Speed and Mixture Adjustments

The following procedure requires the use of a dwell meter, GM tool No. J-29030-B, BT-7610-B or equivalent, a center punch, a hammer, a hacksaw, GM tool No. J-33815, BT-8253-B or equivalent.

The idle air bleed valve and the idle mixture needles are sealed with hardened plugs, to protect the factory settings. These settings are not to be tampered with, except for, cleaning, part replacement or if the carburetor is the cause of trouble.

  1. If necessary to remove the idle air bleed cover, perform the following procedures:
    1. Remove the air cleaner and the gasket.
    2.  
    3. Using masking tape or equivalent, cover the internal bowl vents and the air inlets to the idle air bleed valve.
    4.  
    5. Carefully drill out the idle air bleed cover pop rivet heads.
    6.  
    7. Using a drift and a small hammer, drive out the remaining portions of the rivet shanks.
    8.  
    9. Remove/discard the idle air bleed cover and the masking tape used to cover the vents and the air passages.
    10.  

  2.  
  3. To set the idle air bleed valve, perform the following procedures:
    1. Using the GM tool No. J-33815, BT-8253-B or equivalent, position it in the throttle side D-shaped hole in the air horn casting. The tool's upper end should be positioned over the open cavity next to the idle air bleed valve.
    2.  
    3. Holding the gauging tool down slightly, so that the solenoid plunger is against the solenoid stop, adjust the idle air bleed valve so that the gauging tool will pivot over and just contact the top of the valve.
    4.  

  4.  
  5. Using a new idle air bleed cover and pop rivets, install the cover to the air horn casting.
  6.  
  7. If necessary to adjust the idle mixture needle screws, perform the following procedures to remove the hardened steel plugs:
    1. Remove the carburetor from the engine.
    2.  
    3. Invert the carburetor and drain the fuel from the float bowl.
    4.  
    5. Position the carburetor, in the inverted position, in a holding fixture to gain access to the idle mixture needle plugs.
    6.  

  8.  

When positioning the carburetor, be careful not to damage the linkage, the tubes and other parts protruding from the air horn.

    1. Using a hacksaw, make two parallel cuts into the throttle body; cut on each side of the locator points beneath the idle mixture needle plugs.
    2.  
    3. Using a punch and a hammer, drive the casting segment toward the hardened plug, be sure to drive out the plug.
    4.  
    5. Repeat this process for the other plug.
    6.  

  1. Using the GM tool No. J-29030-B, BT-7610-B or equivalent, turn the idle mixture needle screws clockwise until they are lightly seated, then turn them counterclockwise 3 turns.
  2.  
  3. Using a new carburetor-to-intake manifold gasket, install the carburetor onto the engine, DO NOT install the air cleaner or gasket.
  4.  
  5. Disconnect the vacuum hose-to-canister purge valve and plug it. At the carburetor, disconnect the electrical connector from the Mixture Control (M/C) solenoid.
  6.  
  7. Using a dwell meter, connect it to the M/C solenoid electrical connector and set it on the 6-cyl. scale.
  8.  
  9. Start the engine and allow it to reach normal operating temperatures.
  10.  
  11. Place the transmission in Drive (AT) or Neutral (MT), then adjust the idle mixture needle screws, in 1 / 8 turn increments, until the dwell reading varies within the 25-35° range (be as close to 30° as possible). If the reading is too low, turn the idle mixture needle screws counterclockwise. If the reading is too high, turn the idle mixture needle screws clockwise.
  12.  

Be sure to allow the engine to stabilize between adjustments.

  1. After the adjustment is complete, seal the idle mixture screw openings with silicone sealant, this will prevent any further adjustment of the idle mixture screws and prevent any fuel vapor loss.
  2.  
  3. Adjust the curb idle speed, if necessary.
  4.  
  5. Check and/or adjust the fast idle speed by referring information on the Vehicle Emission Control Information Label in the engine compartment.
  6.  

Float and Fuel Level Adjustment

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Using the GM float gauge tool No. J-34935-1, BT-8420-A or equivalent, to check the float level

The following procedure requires the use of the GM Float Gauge tool No. J-34935, BT-8420-A or equivalent.

  1. Remove the air cleaner from the carburetor.
  2.  
  3. With the engine idling and the choke plate in the Wide-Open position, insert the GM Float Gauge tool No. J-34935, BT-8420-A or equivalent, into the vent hole (slot) of the air horn; allow the gauge to float freely.
  4.  

DO NOT press down on the gauge, for flooding or float damage may occur.

  1. Observe the mark (on the gauge) that aligns with the top of the air horn; the float setting should be within 0.0625 in. (1.5mm) of the specifications.
  2.  

Incorrect fuel pressure will adversely affect the fuel level.

  1. If the float level is not correct, perform the following procedures:
    1. Turn the ignition switch OFF .
    2.  
    3. Disconnect the fuel line, the throttle linkage and/or any electrical connectors from the top of the carburetor (air horn).
    4.  
    5. Remove the air horn-to-fuel bowl screws. Lift the air horn from the fuel bowl and discard the gasket.
    6.  
    7. Bend the float tang (at the needle valve) to the correct specifications.
    8.  
    9. To install the air horn, use a new fuel bowl gasket, install the air horn and the air horn-to-fuel bowl screws.
    10.  
    11. Install the throttle linkage and the fuel line.
    12.  

  2.  
  3. To complete the installation, install the air cleaner. Start the engine and check for fuel leaks.
  4.  

Air Valve Spring Adjustment

See Figure 2



Click image to see an enlarged view

Fig. Fig. 2: Adjusting the air valve spring-M4ME and E4ME carburetors

  1. Using a 3 / 32 in. Allen wrench, loosen the air valve spring lock screw.
  2.  
  3. Turning the tension adjusting screw counterclockwise, open the air valve part way.
  4.  
  5. Turning the tension adjusting screw clockwise, close the air valve, then turn it an additional number of specified turns.
  6.  
  7. Tighten the lock screw, then apply Lithium grease to the spring-to-lever contact area.
  8.  

Choke Coil Lever Adjustment

See Figure 3



Click image to see an enlarged view

Fig. Fig. 3: Adjusting the choke coil lever-E4ME carburetor

  1. Drill out and remove the choke coil housing cover rivets. Retain the choke housing cover, then remove the thermostatic cover and coil assembly from the choke housing.
  2.  
  3. Place the fast idle cam follower on the high step of the fast idle cam.
  4.  
  5. Close the choke valve by pushing up on the thermostatic coil tang (counterclockwise).
  6.  
  7. Insert a drill or gauge, of the specified size, into the hole in the choke housing. The lower edge of the choke lever should be just touching the side of the gauge.
  8.  
  9. If the choke lever is not touching the side of the gauge, bend the choke rod until you see that it does.
  10.  

Fast Idle Cam (Choke Rod) Adjustment

See Figures 4 and 5



Click image to see an enlarged view

Fig. Fig. 4: Using the GM choke valve angle gauge tool No. J-26701, BT-7740 or equivalent, to check the choke valve



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Fig. Fig. 5: Fast idle cam (choke rod) adjustment-E4ME carburetor

The following procedure requires the use of the GM Valve Angle Gauge tool No. J-26701, BT-7704 or equivalent.

  1. Using a rubber band, attach it between the green tang of the intermediate choke shaft and the air horn housing.
  2.  
  3. Open the throttle and allow the choke valve to close.
  4.  
  5. Using the GM Valve Angle Gauge tool No. J-26701, BT-7704 or equivalent, attach it to the choke plate, then perform the following procedures:
    1. Rotate the degree scale until the zero is opposite the pointer.
    2.  
    3. Center the leveling bubble.
    4.  
    5. Rotate the scale to the specified angle degrees.
    6.  

  6.  
  7. Position the cam follower on the 2nd step (against the rise of the high step) of the fast idle cam.
  8.  

If the cam follower does not contact the cam, adjust the fast idle speed screw. Final fast idle speed adjustment MUST BE performed according to the underhood emission control information label.

  1. Center the bubble of the Valve Angle Gauge, by bending the fast idle cam tang.
  2.  

Front (Primary Side) Vacuum Break Adjustment

See Figure 6



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Fig. Fig. 6: Front (primary side) vacuum break adjustment-E4ME carburetor

The following procedure requires the use of the GM Valve Angle Gauge tool No. J-26701, BT-7704 or equivalent.

  1. Using a rubber band, attach it between the green tang of the intermediate choke shaft and the air horn housing.
  2.  
  3. Open the throttle and allow the choke valve to close.
  4.  
  5. Using the GM Valve Angle Gauge tool No. J-26701, BT-7704 or equivalent, attach it to the choke plate, then perform the following procedures:
    1. Rotate the degree scale until the zero is opposite the pointer.
    2.  
    3. Center the leveling bubble.
    4.  
    5. Rotate the scale to the specified angle degrees.
    6.  

  6.  
  7. Apply a vacuum source (18 in.Hg) to retract the vacuum break and plug the air bleed holes.
  8.  
  9. Center the bubble of the Valve Angle Gauge, by turning the adjusting screw.
  10.  

Rear (Secondary Side) Vacuum Break Adjustment

See Figures 7 and 8



Click image to see an enlarged view

Fig. Fig. 7: Plugging the air bleed holes of the vacuum break-E4ME carburetor



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Fig. Fig. 8: Rear (secondary side) vacuum break adjustment-E4ME carburetor

The following procedure requires the use of the GM Valve Angle Gauge tool No. J-26701, BT-7704 or equivalent.

  1. Using a rubber band, attach it between the green tang of the intermediate choke shaft and the air horn housing.
  2.  
  3. Open the throttle and allow the choke valve to close.
  4.  
  5. Using the GM Valve Angle Gauge tool No. J-26701, BT-7704 or equivalent, attach it to the choke plate, then perform the following procedures:
    1. Rotate the degree scale until the zero is opposite the pointer.
    2.  
    3. Center the leveling bubble.
    4.  
    5. Rotate the scale to the specified angle degrees.
    6.  

  6.  
  7. Apply an 18 in. Hg (60 kPa) vacuum source to retract the vacuum break and plug the air bleed holes.
  8.  
  9. Center the bubble of the Valve Angle Gauge by performing one of the following procedures:
    1. Using a 1 / 8 in. Allen wrench, turn the vacuum break adjusting screw.
    2.  
    3. Using a rod bending tool, support the S-rod and bend the vacuum break rod.
    4.  

  10.  

Air Valve Rod Adjustment

See Figure 9



Click image to see an enlarged view

Fig. Fig. 9: Air valve rod adjustment-E4ME carburetor

The following procedure requires the use of an 18 in. Hg (60 kPa) vacuum source and a 0.025 in. plug gauge.

  1. Apply an 18 in. Hg (60 kPa) vacuum source to retract the vacuum break and plug the air bleed holes.
  2.  
  3. Open the throttle and allow the choke valve to close.
  4.  
  5. Using a 0.025 in. plug gauge, position it between the control rod and the slot in the choke valve cam.
  6.  
  7. To adjust, bend (using a bending tool) the air valve rod.
  8.  

Secondary Lockout Adjustment

See Figure 10



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Fig. Fig. 10: Secondary lockout adjustment-M4ME and E4ME carburetors

The following procedure requires the use of a 0.015 in. plug gauge and a rod bending tool.

  1. Pull the choke wide open by pushing out on the choke lever.
  2.  
  3. Open the throttle until the end of the secondary actuating lever is opposite the toe of the lockout lever.
  4.  
  5. Measure the clearance between the lockout lever and the secondary lever.
  6.  
  7. Bend the lockout pin until the clearance is 0.015 in.
  8.  

Unloader Adjustment

See Figure 11



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Fig. Fig. 11: Adjusting the unloader-E4ME carburetor

The following procedure requires the use of the GM Valve Angle Gauge tool No. J-26701, BT-7704 or equivalent, a rubber band and a bending tool.

  1. Using a rubber band, attach it between the green tang of the intermediate choke shaft and the air horn housing.
  2.  
  3. Open the throttle and allow the choke valve to close.
  4.  
  5. Using the GM Valve Angle Gauge tool No. J-26701, BT-7704 or equivalent, attach it to the choke plate, then perform the following procedures:
    1. Rotate the degree scale until the zero is opposite the pointer.
    2.  
    3. Center the leveling bubble.
    4.  
    5. Rotate the scale to the specified angle degrees.
    6.  

  6.  

On a Quadrajet, hold the secondary lockout lever away from the pin.

  1. Adjust and hold the throttle lever in the wide-open position.
  2.  
  3. Center the bubble of the Valve Angle Gauge, by bending the fast idle lever tang.
  4.  

Throttle Position Sensor (TPS)

See Figures 12 and 13



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Fig. Fig. 12: Drilling a hole in the TPS screw cover plug



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Fig. Fig. 13: Using the GM adjusting tool No. J-28696, BT-7967-A or equivalent, to adjust the TPS screw

The throttle position sensor is a position meter, mounted on the carburetor; one end is connected to the ECM and the other to a ground. As the throttle plate opens, the output voltage increases; at wide-open throttle the output voltage is approximately 5V.

The following procedure requires the use of GM Adjustment tool No. J-28696 or equivalent, a digital voltmeter tool No. J-29125-A, a drill, a5/64in. drill bit.

  1. Disconnect the negative battery cable from the battery.
  2.  
  3. Remove the air cleaner and stuff a clean rag into the intake bore to keep the carburetor clean.
  4.  
  5. To remove the throttle position plug cover, perform the following procedures:
    1. Using a 5 / 64 in. drill bit, drill a hole in the aluminum plug covering the throttle position solenoid adjusting screw.
    2.  

  6.  

When drilling the hole in the aluminum plug, be careful not to damage the adjusting screw head.

    1. Using a No. 8, 1 / 2 in. self-tapping screw, install it into the drilled hole.
    2.  
    3. Using a wide blade screwdriver, pry against the screw head to remove the plug, then discard the plug.
    4.  

  1. Using the GM adjusting tool No. J-28696, BT-7967-A or equivalent, remove the throttle position solenoid adjusting screw.
  2.  
  3. Using the digital voltmeter tool No. J-29125-A or equivalent, connect one probe to the center terminal and the other to the bottom terminal of the throttle position solenoid connector.
  4.  
  5. Turn the ignition switch ON with the engine stopped. Install the throttle position solenoid adjustment screw.
  6.  
  7. Using the GM adjusting tool No. J-28696, BT-7967-A or equivalent, install the throttle position solenoid adjusting screw and turn it to obtain a voltage of 0.255V (air conditioning off and at curb idle).
  8.  
  9. After the adjustment is complete, install a new throttle position solenoid plug cover; drive the plug in until it flush with the raised pump lever boss on the casting.
  10.  

If a throttle position solenoid plug is not available, apply Delco Threadlock Adhesive X-10® or equivalent, to the screw threads and repeat the adjustment.

  1. After adjustment, clear the trouble code memory.
  2.  

Mixture Control Solenoid (Plunger Travel)

If the dwell is off at 3000 rpm, perform this check and/or adjustment procedure.

CHECKING

See Figure 14



Click image to see an enlarged view

Fig. Fig. 14: Checking the mixture control solenoid plunger travel-E4ME carburetor

The following procedure requires the use of the GM Float Gauge tool No. J-34935, BT-8420-A or equivalent.

  1. With the engine not running, remove the air cleaner from the carburetor.
  2.  
  3. Insert the GM Float Gauge tool No. J-34935-1, BT-8420-A or equivalent, into the vertical D-shaped vent hole of the air horn; allow the gauge to touch the solenoid plunger.
  4.  

If difficulty is experienced in inserting the gauge into the hole, it may be necessary to grind some of the material from it.

  1. With the gauge released (plunger in the Up position), observe and record the mark (on the gauge) that aligns with the top of the air horn.
  2.  
  3. Press down (lightly) on the gauge until it bottoms, then read and record the mark that aligns with the top of the air horn.
  4.  
  5. Subtract the Up position from the Down position; the difference is the total plunger travel:
    1. If the plunger travel is 1 / 16 - 3 / 16 in. (1.5-4.8mm) and the dwell reading was OK at 3,000 rpm (10°-50°).
    2.  
    3. If the plunger travel is less than 1 / 16 in. (1.5mm) or greater than 3 / 16 in. (4.8mm) or the dwell reading was off at 3,000 rpm, adjust the mixture control solenoid plunger travel.
    4.  

  6.  

ADJUSTMENT

See Figures 15, 16 and 17



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Fig. Fig. 15: Exploded view of the mixture control solenoid assembly-E4ME carburetor



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Fig. Fig. 16: Positioning the mixture control solenoid gauging tool



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Fig. Fig. 17: Adjusting the mixture control solenoid screw

The following procedure requires the use of the GM Mixture Solenoid Gauge tool No. J-33815-1, BT-8253-A or equivalent, and the GM Adjustment tool No. J-28696-10, BT-7928 or equivalent.

  1. Disconnect the negative battery terminal from the battery, then the mixture control solenoid, the throttle position sensor and the idle speed solenoid connectors from the carburetor.
  2.  
  3. To remove the air horn, perform the following procedures:
    1. Remove the idle speed solenoid-to-air horn screws and the solenoid.
    2.  
    3. Remove the choke lever-to-choke shaft screw, rotate the upper choke lever and remove the choke rod from the slot in the lever.
    4.  
    5. To remove the choke rod from the lower lever (inside the float bowl casting), use a small screwdriver to hold the lower lever outward and twist the rod counterclockwise.
    6.  
    7. Remove the fuel pump link from the pump lever; DO NOT remove the pump link from the air horn.
    8.  
    9. From the front of the float bowl, remove the front vacuum break hose from the tube.
    10.  
    11. Remove the air horn-to-fuel bowl screws and lift the air horn straight up from the float bowl; discard the gasket.
    12.  

  4.  

When removing the air horn-to-float bowl screws, be sure to remove the 2 countersunk screws located next to the venturi.

  1. Remove the solenoid adjustment screw, the rich limit stop, the mixture control solenoid plunger, the primary metering rods with the springs, the plastic filler block and the mixture control solenoid.
  2.  
  3. Inspect the carburetor for the cause of an incorrect mixture:
    1. Inspect for a worn mixture control solenoid bore or sticking plunger.
    2.  
    3. Inspect the metering rods for an incorrect part number, sticking condition and improperly installed rods or springs.
    4.  
    5. Inspect for dirt in the jets.
    6.  

  4.  
  5. Using the GM Mixture Solenoid Gauging tool No. J-33815-1, BT-8253-A or equivalent, install it over the throttle side metering jet rod guide and temporarily reinstall the solenoid adjusting screw spring, the mixture control solenoid, the plunger, the rich limit stop and the solenoid adjusting screw.
  6.  
  7. To adjust the solenoid plunger, perform the following procedures:
    1. Using light finger pressure, as close to the plunger shaft as possible, hold the solenoid plunger in the Down position.
    2.  
    3. Using the GM Adjustment tool No. J-28696-10, BT-7928 or equivalent, turn the solenoid adjusting screw clockwise until the plunger contacts the gauging tool.
    4.  
    5. Turn the tool counterclockwise until the plunger breaks contact with the gauging tool.
    6.  

  8.  

When the solenoid plunger contacts both the solenoid stop and the gauge tool, the adjustment is correct.

  1. Noting the position of the tool's tee handle, turn the solenoid's adjusting screw clockwise (counting and recording the number of turns) until the solenoid bottoms against the float bowl.
  2.  
  3. Remove the solenoid adjusting screw, the rich limit stop, the mixture control solenoid, the plunger, the solenoid adjusting screw spring and the gauging tool.
  4.  
  5. Install the solenoid adjusting screw spring, the mixture control solenoid, the plastic filler block, the primary metering rods/springs, the mixture control solenoid plunger, the rich limit stop and the solenoid adjusting screw.
  6.  
  7. Using the GM Adjustment tool No. J-28696-10, BT-7928 or equivalent, turn the adjusting screw clockwise (counting the exact number of turns from Step 7) until the solenoid bottoms against the float bowl.
  8.  
  9. To install the air horn, use a new gasket and reverse the removal procedures. Start the engine and check the dwell at 3000 rpm.
  10.  
  11. To set the engine for dwell inspection, perform the following procedures:
    1. Disconnect and plug the vacuum line-to-canister purge valve.
    2.  
    3. Ground the diagnostic test terminal.
    4.  
    5. Attach a dwell meter to the engine.
    6.  
    7. Operate the engine until normal operating temperature is established; the upper radiator hose is Hot.
    8.  

  12.  
  13. To inspect the dwell, operate the engine at 3000 rpm and check for the following conditions:
    1. If the dwell is 10-50° the mixture control solenoid adjustment is complete.
    2.  
    3. If the dwell is greater than 50°, check the carburetor for a rich condition.
    4.  
    5. If the dwell is less than 10°, check for vacuum leaks or a lean operating carburetor.
    6.  

  14.  

REMOVAL & INSTALLATION



Carburetor
  1. Raise the hood. From inside the vehicle, remove the engine cover.
  2.  
  3. Disconnect the negative battery cable from the battery.
  4.  
  5. Remove the air cleaner and the accelerator linkage.
  6.  
  7. If equipped with an AT, remove the detent cable from the carburetor.
  8.  
  9. Disconnect the cruise control, if equipped.
  10.  
  11. Label and disconnect all of the necessary vacuum lines.
  12.  
  13. Place a shop cloth under the fuel line-to-carburetor connection and disconnect the fuel line from the carburetor; the cloth will catch the excess fuel.
  14.  
  15. Label and disconnect all of the necessary electrical connections.
  16.  
  17. Remove the carburetor-to-intake manifold bolts, the carburetor and the gasket (discard it).
  18.  

To install:
  1. Use a new carburetor-to-intake manifold gasket and install the carburetor onto the manifold. Torque the carburetor-to-intake manifold bolts to 84 inch lbs. (9.5 Nm) or 132 inch lbs. (14 Nm).
  2.  
  3. Connect all of the necessary electrical connections.
  4.  
  5. Place a shop cloth under the fuel line-to-carburetor connection and connect the fuel line to the carburetor; the cloth will catch the excess fuel.
  6.  
  7. Connect all of the necessary vacuum lines.
  8.  
  9. Connect the cruise control, if equipped.
  10.  
  11. If equipped with an AT, install the detent cable to the carburetor.
  12.  
  13. Install the accelerator linkage and air cleaner.
  14.  
  15. Connect the negative battery cable to the battery.
  16.  
  17. Install the engine cover and lower the hood.
  18.  
  19. Start the engine and check for leaks and proper operation.
  20.  

Throttle Position Sensor (TPS)

See Figures 18 and 19



Click image to see an enlarged view

Fig. Fig. 18: Use a suitable tool to install the air horn onto the float bowl-E4ME carburetor



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Fig. Fig. 19: Air horn torque sequence-E4ME carburetor

  1. Disconnect the negative battery cable from the battery, then the mixture control solenoid, the throttle position sensor and the idle speed solenoid connectors from the carburetor.
  2.  
  3. At the air horn, remove the following items by performing the following procedures:
    1. Remove the idle speed solenoid-to-air horn screws and the solenoid.
    2.  
    3. Remove the choke lever-to-choke shaft screw, rotate the upper choke lever and remove the choke rod from the slot in the lever.
    4.  
    5. To remove the choke rod from the lower lever (inside the float bowl casting), use a small screwdriver to hold the lower lever outward and twist the rod counterclockwise.
    6.  
    7. Remove the fuel pump link from the pump lever; DO NOT remove the pump link from the air horn.
    8.  
    9. From the front of the float bowl, remove the front vacuum break hose from the tube.
    10.  
    11. Remove the air horn-to-fuel bowl screws and lift the air horn straight up from the float bowl; discard the gasket.
    12.  

  4.  

When removing the air horn-to-float bowl screws, be sure to remove the 2 countersunk screws located next to the venturi.

  1. To remove the throttle position solenoid from the float bowl, perform the following procedures:
    1. Using a flat tool or a piece of metal, lay it across the float bowl to protect the gasket sealing surface.
    2.  
    3. Using a small prybar, lightly depress the throttle position solenoid sensor and hold against the spring tension.
    4.  
    5. Using a small chisel, pry upward (against the bowl staking) to remove the staking.
    6.  

  2.  

When removing the bowl staking, be sure to apply prying force against the metal piece and not the bowl casting.

    1. Pushing up on the bottom of the throttle position solenoid electrical connector, remove it and the connector assembly from the fuel bowl.
    2.  


To install:
  1. Install the throttle position solenoid/connector assembly, align the groove in the electrical connector with the slot in the float bowl casting. Push down on the assembly so that the connector and wires are located below the bowl casting surface; be sure the green throttle position solenoid actuator plunger is aligned in the air horn.
  2.  
  3. Install the air horn, hold the pump plunger assembly down against the return spring tension. Align the pump plunger stem with the hole in the gasket and the gasket over the throttle position solenoid plunger, the solenoid plunger return spring, the metering rods, the solenoid mounting screws and the electrical connector. Use the two dowel locating pins (on the float bowl) to align the gasket.
  4.  
  5. While holding the solenoid metering rod plunger, the air horn gasket and the pump plunger assembly, align the slot in the end of the plunger with the solenoid mounting screw.
  6.  
  7. While lowering the air horn assembly (carefully) onto the float bowl, position the throttle position solenoid adjustment lever of the throttle position solenoid sensor and guide the pump plunger stem through the air horn casting seal.
  8.  

To ease the installation of the air horn onto the float bowl, insert a thin screwdriver between the air horn gasket and the float bowl to raise the throttle position solenoid adjustment lever while positioning it over the throttle position solenoid sensor.

  1. Install the air horn-to-float bowl screws and tighten all of the screws evenly, using the torquing sequence.
  2.  
  3. Reconnect all of the vacuum and electrical connectors. Clear the trouble code from the ECM memory. Check and/or adjust the throttle position solenoid voltage.
  4.  
  5. Connect the negative battery cable, start the engine, check for leaks and proper operation.
  6.  

Mixture Control Solenoid

The following procedure requires the use of GM Solenoid Adjusting tool No. J-28696-1 or equivalent.

  1. Disconnect the negative battery cable from the battery, then the mixture control solenoid and the Throttle Position Sensor (TPS) electrical connectors from the carburetor.
  2.  
  3. Remove the air horn, by performing the following procedures:
    1. Remove the choke lever-to-choke shaft screw, rotate the upper choke lever and remove the choke rod from the slot in the lever.
    2.  
    3. To remove the choke rod from the lower lever (inside the float bowl casting), use a small screwdriver to hold the lower lever outward and twist the rod counterclockwise.
    4.  
    5. Remove the fuel pump link from the pump lever; DO NOT remove the pump link from the air horn.
    6.  
    7. From the front of the float bowl, remove the front vacuum break hose from the tube.
    8.  
    9. Remove the air horn-to-fuel bowl screws and lift the air horn straight up from the float bowl; discard the gasket.
    10.  

  4.  

When removing the air horn-to-float bowl screws, be sure to remove the 2 countersunk screws located next to the venturi.

    1. Lift the air horn straight up from the float bowl.
    2.  

  1. Using the GM Solenoid Adjusting tool No. J-28696-1 or equivalent, remove the mixture control solenoid adjusting screw.
  2.  
  3. Lift the air horn-to-float bowl gasket from the dowel locating pins and discard it.
  4.  
  5. Remove the plastic filler block from over the float bowl.
  6.  
  7. Lift (carefully) each metering rod from the guided metering jet; be sure to remove the return spring with each rod.
  8.  
  9. Remove the mixture control solenoid-to-float bowl screw, then lift the solenoid and the connector assembly from the float bowl.
  10.  

If a new mixture control solenoid package is being installed, the solenoid and the plunger MUST BE installed as a matched set.

  1. When installing the mixture control solenoid, perform the following procedures:
    1. Align the solenoid's pin with the hole in the raised boss at the bottom of the float bowl.
    2.  
    3. Align the wires of the solenoid's connector in the bowl slot or the plastic insert (if used).
    4.  
    5. Install the solenoid-to-fuel bowl mounting screw and engage the first 6 screw threads (to assure proper thread engagement).
    6.  

  2.  
  3. To complete the installation, use a new gasket and reverse the removal procedures. Calibrate the mixture control solenoid plunger.
  4.  

 
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