DIESEL EXCESSIVE EXHAUST SMOKE ROUGH RUNNING AFTER COLD START

Diesel engines that exhibit exhaust smoke and run rough after cold starting may usually be corrected by dynamic timing. If timing does not correct this condition, check the housing pressure cold advance (HPCA) for proper operation (1981 through 1983 models). Also, check for a sticking advance piston in the injection pump (1980 through 1983 models).

To check for a sticking advance piston, push in on the bottom of the face cam lever on the right side of the injection pump. This will retard timing and cause the engine to run rough if the advance piston is free. If there is no change, the piston is sticking.

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.