FUEL VAPOR LOCKS, SURGES AND / OR STALLS

MODELS: 1982-1985 S/T MODELS WITH 2.8L V6 ENGINES

Some 1982 - 1985 S/T trucks equipped with the 2.8L V6 engine may experience a fuel vapor lock condition (surges or stalls) after the vehicle has been operated on high ambient temperature days or in high altitude areas. This condition usually occurs after a "hot soak" (truck has been driven for approximately 20 minutes and then allowed to sit with the engine off) or after extended highway speed operations.

An in-tank electric fuel pump (See Figure No. 1) and upgraded fuel hoses have been released to assist the fuel pump that is mounted on the engine to correct this condition. If this condition is encountered, it will be necessary to obtain the following parts and applicable service kit (with installation graphics included) and use the attached procedure to correct the condition.

Parts Information

S/T Jimmy requires the following parts:

Part Number Description Quantity ----------- ----------- -------- 15554568 Accessory Kit 1 25115090 Hose Unit 1 12053094 Middle Wiring Harness Assembly (1983-84) 1 12053095 Middle Wiring Harness Assembly (1985) 1 25004166 Sender W/O Pump - 13 Gal. Tank 1 25004162 Sender W/O Pump - 20 Gal. Tank 1 15547947 Pump & Hose Kit (S Only) 1 Kit 15547948 Pump & Hose Kit (T Only) 1 Kit

S/T Pickup and Extended Cab requires the following parts:

Part Number Description Quantity ----------- ----------- -------- 15554568 Accessory Kit 1 25115090 Hose Unit 1 12053092 Middle Wiring Harness Assembly (1982-84) 1 12053093 Middle Wiring Harness Assembly (1985) 1 25004158 Sender W/0 Pump - 13 Gal. Tank 1 25004154 Sender W/0 Pump - 20 Gal. Tank 1 15547949 Pump & Hose Kit (S Only) 1 Kit 15547950 Pump & Hose Kit (T Only) 1 Kit Instructions

CAUTION:

To prevent possible accidents when working on the fuel system, disconnect the vehicle battery ground cable and drain the fuel lines into an approved container. Provide the appropriate fire fighting and safety equipment in accordance with local fire and safety regulations.

Note: Refer to installation sheets, P/N 15528793, (included as part of the accessory kit) and P/N 15547951 (included as part of the pump and hose kits) for specific instructions on model applications.

Note: Refer to Section 6C of the S-15 Service Manual for fuel tank and sender removal and installation procedures.

1. Raise the vehicle.

2. Remove the fuel tank.

3. Remove the fuel tank sender and discard.

4. Install intank pump and wires for the pump on new sender (see Figure No. 1).

5. Install sender and pump in fuel tank.

6. Install the new floroelastomer fuel hoses to sender.

7. Install the jumper harness (harness included with accessory kit) on sender harness. See accessory kit graphic sheets 14 and 15.

8. Install the rear harness (included with accessory kit) on the chassis. See accessory kit graphic sheets 14 and 15.

9. Reinstall the fuel tank in vehicle.

CAUTION:

Care must be taken when attaching the fuel hoses to the fuel tank. On the 1982-84 model, the fuel return and fuel vapor lines are reinstalled in a different position on the sender. Follow the instructions provided in the accessory kit. Improper installation of these hoses could overfill the vapor canister and flood the engine.

10. Install the new middle wiring harness on the chassis. See accessory kit graphic sheets 9, 10, 11, 12, and 13.

11. Remove the middle fuel hoses and clamps (Jimmy only) from the chassis, and install the new floroelastomer hoses and clamps. Tighten the clamps to the proper torque - 1.8-2.2 N.m (16-20 in. lbs.). See fuel hose kit instruction sheet 3.

12. Remove and discard front fuel hoses and clamps (all models) from the chassis and engine, and install the new floroelastomer hoses and clamps. Tighten the clamps to the proper torque - 1.8-2.2 N.m (16-20 in. lbs.). See fuel hose kit instruction sheets 1 and 2.

13. Lower vehide.

14. Install new fuel pump relay. See accessory kit graphic sheet 2.

15. Install fuel pump relay harness and attach to the new middle wiring harness. See accessory kit graphic sheets 2 and 3.

16. Route the new fuel pump relay harness down to the starter motor as per graphics induded with accessory kit. See accessory kit graphic sheets 3 and 4.

17. Raise the vehicle.

18. Attach the harness to the starter motor. See accessory kit graphic sheet 4.

19. Check all hoses and wires for proper routing.

20. Lower the vehicle.

21. Reset carburetor float level to 1/8" lower than the original specification. See the Light Duty Service Manual for the original specification.

22. To test the intank pump operation, temporarily disconnect inlet fuel hose to mechanical fuel pump. Connect the battery lead and turn on the ignition switch. When fuel flows from the fuel line, shut off ignition switch. Use an approved container to catch the fuel.

23. Reattach the fuel hose and tighen the clamp to the proper torque - 1.8-2.2 N.m (16-20 in. lbs.).

24. Start up the vehicle and check all the fuel lines for leaks.

25. Road test the vehicle.

Also included in the instructions are the wiring diagrams for the relay assembly and fuel pump.

The recommended time to perform the operation is as follows:

S/T Jimmy - 3.0 hrs. Add .3 hr. if equipped with fuel tank shield, NY1.

S/T Pickup - 2.7 hrs. Add .3 hr. if equipped with fuel tank shield, NY1. Add .5 hr. if equipped with optional tank, NK2.

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.