1990 Pontiac LeMans GSE, AutomaticFACTORY OEM SERVICE PROCEDURE

Fuel Pressure

WARNING: ALWAYS relieve fuel pressure before disconnection any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components.

Fuel Pressure Release

To remove any residual system pressure, remove fuel pump fuse (No. 16, 20-amp) from fuse block in passenger compartment. Start and run engine until engine stalls. Engage starter again for about 3 seconds. Turn ignition off and install fuse.

Fuel Pump Relay

Use circuit wiring diagram and diagnostic flow charts (A-5) and (A-7) to diagnose and service fuel pump relay faults. See Fig 1 -3.

Checking Fuel Pressure

1) With fuel pressure relieved, remove air cleaner and gasket. Remove flexible steel fuel line from between throttle body and fuel filter. When removing fuel line, always use 2 wrenches to prevent damage. Install fuel pressure gauge between throttle body and fuel filter.

2) Start vehicle and observe fuel pressure reading. Fuel pressure should be 9-13 psi (.6-.9 kg/cm2 ). If fuel pressure is not within specification, refer to diagnostic flow charts (A-5) and (A-7) in this article. See Fig 1 -3.

3) Release fuel pressure as described in step 1). Remove fuel pressure gauge. To check fuel pump volume, insert end of fuel line into a container. Apply battery voltage to terminal "G" of the ALDL test connector. See Fig 4 .

4) Fuel pump should supply at least 1.0 pt. (.8 L) in 30 seconds. If flow is less than specified, check for restricted fuel line. If fuel line is okay, replace fuel pump. Install steel flex line between fuel filter and throttle body. Start engine and check for leaks. Install air cleaner and gasket.

Fig 1: Fuel Pump Relay Diagnostic Flow Chart (A-5)
G94615Courtesy of GENERAL MOTORS CORP.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.

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