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Friday, August 28, 2009

Electric Fuel Pump Testing - 1994 Pontiac Grand Prix

Connect pressure gauge J–34730–1, or equivalent, to fuel pressure test point on the fuel rail. Wrap a rag around the pressure tap to absorb any leakage that may occur when installing the gauge.

Turn the ignition ON and check that pump pressure is 24–40 psi. (165–276 kPa)

Start the engine and allow it to idle. The fuel pressure should drop to 28–32 psi (193–221 kPa) due to the lower manifold pressure.

NOTE: The idle pressure will vary somewhat depending on barometric pressure. Check for a drop in pressure indicating regulator control, rather than specific values.

If the fuel pressure drops, check the operation of the check valve, the pump coupling connection, fuel pressure regulator valve and the injectors. A restricted fuel line or filter may also cause a pressure drip. To check the fuel pump output, restrict the fuel return line and run 12 volts to the pump. The fuel pressure should rise to approximately 75 psi (517 kPa) with the return line restricted.

Before attempting to remove or service any fuel system component, it is necessary to relieve the fuel system pressure.

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