ENGINE DRIVEN FUEL PUMP TEST PROCEDURE

VEHICLES AFFECTED: All With Engine Driven Large Diameter Fuel Pumps

The following is a field test procedure for vehicles with large diameter, engine driven fuel pumps.

Models with fuel return lines:

A. Engine at normal operating temperatures.

B. Disconnect fuel hose from fuel tank to pump at the pump.

C. Connect known good vacuum gauge to fuel pump suction pipe.

D. Crank engine for 10 seconds, vacuum gauge should read 15 inches of vacuum and hold there for at least 15 seconds.

If pump does not pass this test, replace pump.

Models without fuel return lines:

A. Engine at operating temperatures.

B. Disconnect fuel hose from fuel tank to pump at the pump.

C. Connect known good vacuum gauge to fuel pump suction pipe.

D. Crank engine for 10 seconds, vacuum gauge should read 12 inches of vacuum but due to design will not hold this reading.

If this 12 inch reading is not obtained during cranking for 10 seconds, replace pump.

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.