See Figure 1
- Position the fast idle speed adjusting screw so that it contacts the second highest step of the cam. Move the choke valve toward the closed position with light pressure on the choke linkage.
- Insert a 0.070" drill bit between the upper edge of the choke plate and the wall of the air horn on trucks with automatic transmission; 0.060" on trucks with manual transmission.
- If adjustment is necessary, bend the fast idle link at the angle until the specified drill fits between the choke plate and the wall of the air horn.
See Figure 2
- If the adjustment is to be made on the engine (with the engine running at curb idle), back off the fast idle screw until the choke can be closed to the kick position. Note the number of screw turns required so that the fast idle can be returned to the original adjustment.
- If the adjustment is to be made off the engine, open the throttle valve and move the choke to its closed position. Release the throttle first and then release the choke. Disconnect the vacuum hose from the carburetor body and apply a vacuum of at least 15 in.Hg.
- Apply sufficient closing pressure to the choke lever to provide a minimum valve opening without distorting the diaphragm link (which connects the choke lever to the vacuum diaphragm). Note that the cylindrical stem of the diaphragm will extend as its internal spring is compressed. This spring must be fully compressed for the proper measurement of the vacuum kick adjustment.
- Using a 5 / 64 " Allen wrench in the diaphragm adjuster, adjust the clearance so that a 0.150" drill bit can fit between the choke valve and the wall of the air horn.
- Remove the drill bit.
- Refit the vacuum hose to the carburetor body (if it had been removed) and return the fast idle screw to its original location.
- With no vacuum applied to the diaphragm, the choke valve should move freely between its open and closed positions. If it does not move freely, examine the linkage for misalignment or interference which may have been caused by the bending operation. If necessary, repeat the adjustment to provide the proper link operation.
See Figure 3
- Hold the throttle valve in the wide open position.
- Insert a 1 / 4 " drill bit between the upper edge of the choke valve and the wall of the air horn.
- With a finger pressing lightly against the choke plate, a slight drag should be felt as the drill is being withdrawn.
- If adjustment is necessary, bend the unloader tang on the throttle lever until the correct opening is obtained.
See Figure 4
- Place the throttle in the curb idle position.
- Make sure that the pump operating link is in the #2 (upper) hole in the throttle lever.
- Measure the length of the operating link. The length should be 1.61" on 1983-84 models; 1.75" on 1985-87 models. If not, bend it at the U-bend.
See Figure 5
- Run the engine to normal operating temperature.
- Remove the air cleaner and disconnect and plug the EGR vacuum line. Disconnect the vacuum hose at the heated air temperature sensor. Plug the hose. Remove the air cleaner and disconnect and plug the 3 / 16 " hose at the canister. Remove the PCV valve from the rocker cover and allow it to draw fresh air.
- Disconnect and plug the vacuum advance hose at the distributor. Disconnect the engine harness lead at the oxygen sensor. Ground the harness lead. Don't put any stress on this lead! Allow the engine to run for at least 2 minutes after disconnecting the O 2 sensor.
- Open the throttle slightly and place the fast idle screw on the second highest speed step of the cam.
- With the choke fully open, turn the fast idle speed screw in or out until the engine speed listed on your truck's underhood sticker is reached.
- Reposition the screw on the cam after each adjustment to provide the correct closing torque.
- Remove the jumper wire, reconnect the vacuum hoses and install the air cleaner.
See Figure 6
- Remove the carburetor.
- Remove the air horn.
- Invert the carburetor body. THE PUMP INTAKE CHECK BALL WILL DROP OUT. BE SURE TO CATCH IT!
- Allow the weight of the floats to rest on the needle valve. Hold your finger against the hinge pin retainer to fully seat it in the float pin cradle.
- Using a straightedge, the floats should just touch the straightedge at the point on the floats farthest from the fuel inlet.
- If adjustment is necessary, bend the float tang. Bend either float arm to equalize the individual float positions.
See Figure 7
- Run the engine to normal operating temperature.
- Disconnect and plug the EGR vacuum line. Connect a jumper wire between the carburetor switch and a good ground. Disconnect and plug the 3 / 16 " hose at the canister. The air cleaner cannot be removed, but should be propped up to gain access to the carburetor. Remove the PCV valve from the rocker cover and allow it to draw fresh air.
- Turn on the air conditioning and set the blower to LOW.
- Disconnect the compressor clutch wire.
- On models without air conditioning, connect a jumper wire between the battery positive pole and the solenoid idle stop lead wire.
- Open the throttle slightly and allow the plunger to extend.
- Remove the adjusting screw and spring from the solenoid.
- Insert a 1 / 8 " Allen wrench into the solenoid and adjust the engine speed to 850 rpm.
- Turn off the air conditioning and reconnect all wires and hoses.