7.Propane-Assisted Idle Set Procedure

Fig.36. Propane Assisted Idle Speed and Mixture Adjustment:

Tampering with the carburetor is a violation of Federal law. Adjustment of the carburetor idle airfuel mixture can only be done under certain circumstances as explained below. 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.

950 RPM R-9503A R-9504A
R-9750A R-9751A

975 RPM R-9505A R-9506A
R-9752A R-9753A

105ORPM R-9822A R-9823A

1100 RPM R-9824A R-9825A
R-9937A R-9938A
(1) Set the parking brake and place transaxle in neutral. Turn off all lights and accessories. Connect
a tachometer to the engine. Start the engine and allow it to warm up on the second highest step on the fast idle cam until normal operating temperature is reached. Return engine to curb idle.
(2) Disconnect and plug the vacuum hose at the EGR valve. Disconnect the vacuum hose to the heated air door sensor at the three way connector, and in its place, install the supply hose from the propane bottle. Make sure that both valves are fully closed and that the bottle is upright and in a safe location.
(3) Unplug the connector at the radiator fan and install a jumper wire so that the fan will run continuously. Remove the PCV valve from the moulded rubber connector and allow the valve to draw underhood air. Disconnect and plug the 3/16 inch diameter control hose at canister. Connect a jumper wire between carburetor switch and ground.
(4) Open the propane main valve, With the air cleaner in place, slowly open the propane metering valve until maximum engine rpm is reached. When too much propane is added, engine speed will decrease. "Fine tune" the metering valve for the highest engine rpm.

Fig.36. Propane Assisted Idle Speed and Mixture Adjustment:

(5) With the propane still flowing, adjust the idle speed screw on top of the solenoid to get the specified propane rpm. "Fine tune" the propane metering valve to get the highest engine rpm. If there has been a change in the maximum rpm, re-adjust the idle speed screw to the specified propane rpm. (Fig. 36).
(6) Turn off the propane main valve and allow engine speed to stabilize. With air cleaner in place, slowly adjust the mixture screw to achieve the specified idle set rpm. Pause between adjustments to allow the engine speed to stabilize.
(7) Turn on the propane main valve. "Fine tune" the metering valve to get the highest engine RPM. If the maximum engine speed is more than 25 rpm different than the specified propane rpm repeat steps 4 through 7.
(8) Turn off both valves on the propane bottle. Remove the propane supply hose and reinstall the vacuum hose.
(9) On non air conditioned vehicles, perform the fast idle speed adjustment and reinstall the concealment plug. The plug can be installed with the carburetor on the engine.
(10) On air conditioned vehicles, perform the Air Conditioning Idle Speed, Idle Set RPM, and Fast Idle Speed adjustments. Replace the concealment plug. The plug can be installed with the carburetor on the engine.