DIESEL ROUGH IDLE DAMAGED PUMP SHAFT SNAP RING

Some 1982-1983 trucks equipped with the 6.2L diesel engine may experience a rough idle condition. This condition may be caused by the injection pump main shaft snap ring.

If the snap ring is bent rearward, the governor arm can contact the ring causing a rough idle.

The snap ring may have been bent during initial pump assembly or can be bent during repair of the pump.

The snap ring is used to retain the drive shaft in the pump.

If a vehicle is received with a rough idle condition, the following procedure is recommended:

1. Inquire as to the date of problem occurrence.

A. If new, the snap ring may have been bent during initial pump assembly.

B. If after pump removal/repair, the snap ring may have been bent during the repair.

C. If neither A nor B, then a bent ring is not likely and this bulletin does not apply.

2. If A or B above does apply and the condition is only a rough idle with smooth operation above 1,000 RPM, proceed to Step 3.

3. Remove the injection pump housing cover. (Since the housing cover is full of fuel, use adequate absorption material around the pump.)

4. Using a flashlight, look between the forward edge of the housing and the governor. The main shaft will be visible below the governor. Where the main shaft enters the forward edge of the housing, a snap-ring should be visible. The use of a mirror may help to get a better view. Refer to sketch.

5. If the snap ring appears to be bent out of the shaft groove rearwards towards the governor, the ring must be replaced.

6. To replace the snap ring, the injection pump must be removed and should be repaired at an authorized pump repair facility.

7. If the ring is not bent, the rough idle is due to some other cause such as a fuel line air leak, timing, etc.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.