REDUCED PERFORMANCE UNDER HARD ACCELERATION

VEHICLES AFFECTED: 1983-84 'F' Series Vehicles Equipped With 5.0L High Output V8 4BBL Engines (L69)

Some 'F' Series equipped with the L69 engine may experience a reduction in performance in the form of hesitation or sag under hard acceleration. This condition usually occurs at high ambient temperatures when the engine is hot and may be due to fuel vapor lock. Fuel vapor lock is temporary fuel starvation that is most likely to happen upon acceleration after a short soak of extended idle period.

To repair this condition, it will be necessary to install vapor lock fix kit, P/N 14085385. This kit utilizes a low pressure (3 psi) electric in-tank pump.

The fuel vapor lock fix kit has detailed instruction sheets for installing all parts found in the kit and for reworking existing grommets on the vehicle. The instruction sheets do not show parts that have to be removed in order to install kit parts. Use the appropriate shop manual procedures where indicated.

1. Disconnect battery.

2. Remove fuel tank to install new pump and sending unit (Ref. to Shop Manual).

CAUTION:

Care should be taken when removing exhaust pipe bolts from the converter flange to avoid breaking the bolts.

NOTICE: New fuel feed, return and vent hoses must be changed because of material composition.

3. The following interior trim items must be removed to install new body wire harness assembly into existing harness conduit (under carpeting) and into instrument panel connector.

A. Remove instrument panel sound absorber (hush panel) L.H. (Ref. to Shop Manual)

B. Remove shroud side trim finishing panel - L.H. (Ref. to Shop Manual)

C. Remove sill plate and carpet retainer - L.H.

D. Remove body lock pillar trim finishing panel - L.H. (Ref. to Shop Manual)

E. Remove spare tire trim finishing panel.(Ref. to Shop Manual)

F. Remove rear trim panel. (Ref. to Shop Manual)

G. Remove quarter lower trim finishing panel L.H. (Ref. to Shop Manual)

H. Remove quarter upper trim finishing panel - L.H. (Ref. to Shop Manual)

4. Remove L.H. tail lamp assembly to route the body harness assembly from under body to passenger compartment. (Refer to Shop Manual)

NOTICE: The lamp assembly wiring does not need to be disconnected.

5. The following underhood operations must be performed to install the new fuel pump and oil pressure switch assembly, fuel pump harness assembly, and fuel pump relay assembly.

A. Remove air cleaner. B. Disconnect brake vacuum pipe at rear of carburetor. C. Disconnect throttle cable and springs. D. Disconnect throttle cable bracket. E. Remove oil pressure sending unit.

NOTICE: New fuel feed and return hoses (at pump) must be changed because of material composition. If vehicle is not equipped with rear window washer option, remove existing body plug and install grommet supplied in kit (ref. instruction sheet No. 4, View C).

6. Reassemble all parts removed and reconnect battery.

7. Perform electrical check per instruction sheet No. 6.

NOTICE: If pump does not work, check the two (2) in-line fuses in the new jumper harness assembly.

8. Check for oil leaks at oil sender unit.

Use most applicable Labour Operation from Canadian Labour Time Guide and Claim.

4.9 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.