HARD OR NO START AFTER HOT SOAK
MODELS AFFECTED: 1981 DE VILLE, BROUGHAM, ELDORADO AND SEVILLE 198i-1984 LIMOUSINE
Some 1981-1984 vehicies equipped with the V8-6-4 engine may experience either a hard or no start condition when the engine has reached normal operating temperatures and is turned off and allowed to sit for a 30 to 45 minute period in high ambient temperatures (hot soak). This condition may result from fuel vaporizing in the fuel meter assembly due to the transfer of heat from the engine to the throttle body assembly. A new thicker service throttle body gasket (P/N 1642864) is available through GMSPO to address this condition.
Before replacing the throttle body gasket, the following procedure should be used to verify proper fuel system operation.
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.
1. Install a 0-15 PSI fuel pressure gauge (from J29658, J35314 or equivalent) to the service fuel pressure tap. Note fuel pressure with the engine running. Fuel pressure should remain steady within the 9-12 PSI range. If not, refer to DFI chart #4 "Fuel System Diagnosis" in the 1981 Service Information Manual.
2. Monitor and record the fuel pressure after the engine is turned off. Again record fuel pressure after a 30 minute hot soak. The final pressure should be within 2 PSI of the starting fuel pressure. Should the fuel pressure drop more than 2 PSI, restrict the fuel feed and return lines and repeat test to evaluate fuel pressure drop. If the fuel pressure continues to drop more than 2 PSI in 30 minutes, fuel is leaking internally within the fuel meter pressure regulator assembly. If the fuel pressure does not drop more than 2 PSI, fuel was leaking internally in the fuel pump or fuel pump coupler.
3. Check for a low fuel pump output pressure by disconnecting the fuel return line at the throttle body and install a plug in the throttle body opening. Note fuel pressure. Fuel pressure should increase to 15 PSI or greater, if not replace fuel pump.
4. Insulate the throttle body from the engine, by installing the new service throttle body gasket P/N 1642864.
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.
