ENGINE OIL CONSUMPTION
In cases where initial diagnosis for external oil loss (leaks) has not shown a possible cause, and when there is no obvious indication that the oil is being consumed internally within the engine, before proceeding to tear down the engine the fuel tank evaporative canister vent hose should be examined for signs of oil passing through it.
The fuel tank evaporative canister vent hose is connected to the base of the evaporative canister and the vent hose inlet is located in a hole in the left hand side wheelhouse panel.
Withdraw the vent hose from the wheelhouse panel and examine vent hose intake for signs of oil, replace vent hose.
If evidence of oil is found inside the vent hose, this indicates that oil is leaking through the fuel pump from the cylinder head.
This condition can occur when the fuel pump oil seal is damaged. This permits oil from the cylinder head to pass into the fuel pump vent cavity and hence through the fuel pump breather hose to the canister vent hose which acts as a drain. In this event, the fuel pump should be replaced using the following parts available from GMSPO, for the appropriate model years.
1985 - 86 P/N 94443067
1987 - 88 P/N 94443068
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.