ENGINE STALLS, REDUCED DRIVE- ABILITY AFTER COLD START

VEHICLES AFFECTED: 1988 DEVILLES, FLEETWOODS, ELDORADOS AND SEVILLES

Some 1988 Cadillac models equipped with a 4.5L engine may experience an engine stall, engine roughness or a reduced driveability condition following an engine start in cold ambient temperatures. This condition is not usually experienced during warm engine operation or in warm ambient temperatures and may be intermittent in nature. Fuel pressure may drop to 4-8 psi (28-55 kPa) when the condition occurs.

This condition may be caused by an oversized fuel pressure relief spring in the electric in-tank fuel pump. Fuel pumps built between December 3, 1987 (Julian Date 3377) and January 31, 1988 (Julian Date 0318) may be affected, refer to Figure 1, Item 2. The over-sized pressure relief spring reduces the pressure limit at which fuel pump bypass occurs. If internal fuel pump pressure goes high, as during a cold start, the fuel pump may go into a full bypass mode and not return to normal operation. Fuel is discharged out of the fuel pump relief port directly back into the fuel tank. The corresponding drop in fuel pressure to the throttle body results in the driveability and/or stalling condition.

To diagnose and repair this condition, the following steps should be performed:

NOTE: This procedure may be performed with the engine warm or cold.

1. Install a 0-60 psi (0-400 kPa) pressure gauge to the Schrader valve on the fuel supply line at the throttle body.

2. Start the engine and note the fuel pressure. Normal fuel pressure should be 10-12 psi (69-83 kPa). If fuel pressure is at or below 9 psi (62 kPa) replace the fuel pump. If pressure is within the normal range, proceed to step 3.

3. Allow the engine to run for 30 seconds to stabilize fuel flow. Using smooth-jawed needle nose pliers, clamp the fuel return line at the flex hose near the fuel tank, refer to Figure 2, for approximately 15 seconds. Release the clamp and note fuel pressure. If fuel pressure is at or below 9 psi (62 kPa), replace the fuel pump. If fuel pressure is above 9 psi (62 kPa), refer to Section 6E-A, "DFI System Diagnosis" in the Service Information Manual.

A new fuel pump has been released for service use. This pump contains a revised pressure relief spring and is available from GMSPO using the following part numbers:

Eldorado/Seville: 25116285 DeVille/Fleetwood: 25116286

Use applicable labour operation and claim 1.2 hours.

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.