For 1990-2009 cars

# SERV. INFO. FOR V-8 & V-6 ENG. SEVERAL ITEMS COVERED

Hard Start In Cold weather

Hard starting in cold weather can be caused by using SAE 30 weight oil in a diesel engine. 10W 30 oil should be used where temperatures below -10 DEG (14 DEG F) are expected.

Valve Cover Removal

Injection pump lines may be removed from either the left or right sides as required, without removing injection pump. When performing any service on a diesel engine that requires valve cover removal, always remove the pump lines completely. Never disconnect them from the injector nozzles and try to positon out of the way. This will cause damage to the lines and result in a poor running engine.

Excessive Exhaust Smoke And Rough Running 1980-1983 Diesel Engines

Diesel engines that exhibit excessive 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 model.

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 the timing and cause the engine to run rough if the advance piston is free. If there is no change, the piston is sticking.

Diesel Timing Meter

Snap-On Corporation advises that luminosity probes are being damaged by being overtorqued in the cylinder head. This cracks the quartz and allows soot to get behind the lens where it cannot be cleaned. In some cases, meters have been returned for repair when only the probe was at fault. Before the probe is used, hold it up to the light to make sure it is clear. When installing the probe in the cylinder, do not exceed the torque specification of 11 N.m (lbs. ft.)

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.