For 1990-2009 cars

# HOT FUEL HANDLING ENGINE SURGE AFTER HOT SOAK

#### VEHICLES AFFECTED: "F" MODELS; 1983-85 WITH 3C 5.0L V8 (VIN CODE G) ENGINES AND 1983-86 WITH LG4 5.0L V8 (VIN CODE H) ENGINES

Customer comments of engine surge after hot soak may be received. A hot soak is when a vehicle has reached normal operating temperature, then parked with engine off for a short time and then restarted and immediately driven. The hot soak condition is more evident with higher ambient temperatures and the resultant engine surge is caused by excessive fuel vapour in the carburetor bowl. This fuel vapour is created by the temperature difference between the carburetor bowl and the fresh fuel coming from the fuel tank upon restart. Another source of excessive fuel vapour is the charcoal canister which has become saturated during the hot soak.

The following is a suggested sequence for diagnbsing and repairing driveability comments stemming from a hot soak condition.

1. Determine that surge is not due to mechanical problem and/or misadjustments; carburetor float level, fuel delivery, thermac operation, ignition timing, etc.

2. If it has been determined that the vehicle meets specifications and hot soak surge is still present, proceed to step #3.

3. Install carburetor primary metering jets per bulletin 86-650-102.

4. Road test vehicle for surge after hot soak. If surge is still present proceed to step #5.

5. Install evaporative canister vacuum control harness P/N 10077501 per bulletin 86-650-113.

6. Road test vehicle for surge after hot soak. If surge is still present proceed to step #7.

7. Install auxiliary blower fan kit P/N 14094395 per bulletin 87-650-110.

#### Warranty Information:

Use labour operation numbers and labour times published in referenced bulletins.

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.