Standard Procedure - Low Pressure Fuel Pump Test: Notes

NOTE: Assure fuel tank quantity and proper fuel gauge operation. Assure that the fuel pump fuse or relay is not open. Capture any fuel spillage and store in appropriately marked containers.

NOTE: When the ignition switch is turned to the On position the fuel pump will begin to run for 20-30 seconds and then it stops.

The low pressure pump draws fuel out of the fuel tank module mixing bowl and pushes the fuel towards the fuel filter. If the pressure reading is below specification, look for damaged or leaking fuel lines or a restricted fuel filter. If no problem is found with the fuel system replace the low pressure fuel pump.

Disconnect the negative battery cable.
Connect a fuel gauge to the low pressure fuel supply to the high pressure pump (Fig 1 ).

Fig 1: Connecting Fuel Gauge To The Low Pressure Fuel Supply To The High Pressure Pump
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Connect negative battery cable.
Turn the ignition to the On position and observe the fuel gauge reading (Fig 2 ).

Fig 2: Observing The Fuel Gauge Reading
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If the fuel pressure is within specification, reconnect the fuel line to the high pressure pump and continue with the diagnostics. If the fuel pressure is below specification, disconnect the low pressure fuel pump input line to the fuel filter and re-test following the steps above (Fig 3 ).

If the fuel pressure is below specification, replace the fuel pump. If the fuel pressure is equal to the specification, replace the fuel filter.

Fig 3: Testing Fuel Pressure At Fuel Filter

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