Standard Procedure - Low Pressure Fuel Pump Test

Fig 1: Fuel Gauge Connect At High Pressure Pump

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The low pressure pump draws fuel out of the fuel tank module mixing bowl and pushes the fuel towards the fuel filter then to the engine mounted high pressure fuel pump. 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.

1. Disconnect the negative battery cable.
2. Connect a fuel gauge to the low pressure fuel supply to the high pressure pump (4). See Fig 1.
3. Connect negative battery cable.
   Fig 2: Fuel Pressure Test At High Pressure Pump

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4. Turn the ignition to the On position and observe the fuel gauge reading. See Fig 2.

Fig 3: Fuel Pressure Test At Filter

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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 (1) and retest following the steps above. See 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.