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Engine - No Start After Extended Storage

90chevy23
GMC NUMBER: 90-6C-89

GROUP: 6C ENGINE FUEL

DATE: SEPTEMBER, 1990

CORPORATE
NUMBER: 066302
SUBJECT: ENGINE WILL NOT START AFTER EXTENDED STORAGE

MODELS: ALL 1985-90 LIGHT TRUCKS WITH THROTTLE BODY FUEL INJECTION AND 2.5L, 2.8L, 4.3L, 5.OL, 5.7L, OR 7.4L ENGINES



Some 1985-90 light trucks equipped with throttle body injection (TBI) engines (see list below) may experience a condition where fuel delivery to the engine is interrupted causing a no start. This condition may be caused by deterioration of the in-tank fuel pump coupler hose located between the sending unit assembly and the fuel pump. The deterioration is caused by prolonged high ambient temperatures in combination with low fuel volumes (or stale fuel) and extended vehicle storage.

FIGURE 1:




DIAGNOSTIC PROCEDURE See fuel system pressure test (see Figure 1).

Figure No. 2:




REPAIR PROCEDURE

Vehicles that are diagnosed as exhibiting this condition may be repaired by replacing the original coupler hose (see Figure 2) with a new Viton coupler hose kit, P/N 25028041. The kit consists of a new Viton hose and two clamps.

Parts are expected to be available on August 27, 1990. Until then normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. GMSPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the parts will be shipped premium transportation at dealer's expense. All other order types will be canceled as incorrectly ordered while 400 control is in place.

WARRANTY INFORMATION For vehicles repaired under warranty use:
Labor Operation: J5590

Refer to the labor time guide for applicable labor times for various models.
FUEL SYSTEM PRESSURE TEST ALL ENGINES



Circuit Description:
When the fuel pump is running, fuel is delivered to the injector(s) and then to the regulator where the system pressure is controlled to about 62 to 90 kPa (9 to 13 psi). Excess fuel is then returned to the fuel tank.

FIGURE 1:




Test Description: Numbers below refer to circled numbers on diagnostic chart.
1. Pressure, but less than 62 kPa (9 psi) falls into two areas:
^ Regulated pressure but less than 62 kPa (9 psi) - Amount of fuel to injector OK but pressure is too low. System will be lean running and may set Code 44. Also, hard starting cold and poor overall performance.
^ Restricted flow causing pressure drop - Normally, a vehicle with a fuel pressure of less than 62 kPa (9 psi) at idle will not be driveable. However, if the pressure drop occurs only while driving, the engine could surge and stop when pressure is too low.
2. Restricting the outlet side of the gage allows the pump to develop its maximum pressure (dead head pressure). With battery voltage applied to the pump test terminal, fuel pressure should rise to 90
to 103 kPa (13 to 15 psi) as the pressure gage outlet hose is gradually pinched.
3. This test determines if the high fuel pressure is due to a restricted fuel return line or a throttle body pressure regulator problem.

Diagnostic Aids:

^ If the vehicle is equipped with a fuel module, the module must be disconnected before performing the fuel system pressure test. Refer to SECTION 4 of the Fuel and Emissions Manual.

^ Fuel system is under pressure. To avoid fuel spillage, refer to procedures in SECTION 4 for testing or making repairs requiring disassembly of fuel lines or fittings.
^ On V6 or V8 engines, the fuel pressure drops to almost zero psi after pump shuts "OFF".