LOSS OF ENGINE POWER DURING HARD BRAKE APPLICATION

VEHICLES AFFECTED: 1985 FWD DeVille and Fleetwood with HT4100 Engine -----------------------------------

Some 1985 front-wheel drive Devilles and Fleetwoods equiped with the HT4100 engine may experience a loss of engine power during hard brake application (panic stop) with one-half tank of fuel or less. The condition is caused by low fuel pressure due to fuel displacement from the in-tank reservoir during panic stops.

A revised fuel tank (P/N 25527547) with a deeper well to provide a larger reservoir of fuel at the fuel pump pickup has been released for service. The revised fuel tank supersedes the previous design.

Cars suspected of having the condition described above should be diagnosed using the following procedure:

1. Ensure the vehicle has 7 litres (2 gallons) or less of fuel.

2. Attach a fuel pressure gauge to the fuel pressure tap located on the fuel feed line.

CAUTION:

When taking the following fuel pressure readings, be sure the fuel pressure gauge is securely attached to the pressure test point. Be careful to route the pressure gauge hose away from the exhaust manifold, any other hot surfaces, and any sharp edges that could cut or damage the hose. Failure to do so may result in a fuel leak while diagnosing the car.

3. Tape the fuel gauge to the windshield of the car.

4. Drive the car and observe fuel pressure while sharply applying the brakes.

If the fuel pressure fluctuates more than 13.5 kPa (2 psi) during braking, replace the fuel tank with P/N 25527547.

Care should be taken when installing the new fuel tank to position the fuel sending unit pick up filter-strainer correctly. A mispositioned filter-strainer may result in a lose of fuel pressure under various driving maneuvers. The fuel sending unit filter-strainer should be positioned so that the long end of the filter-strainer is pointing toward the front of the car when installed. Be careful not to bend or kink the filter-strainer when installing. Refer to Service Manual Section 6C for removal and installation procedures.

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.