The output of the fuel transfer pump can be checked two ways.
Test 1: Measure the output pressure using an in-line pressure gauge.
Test 2: Measure the flow volume.
Test 1: Output Pressure Test (Diaphragm Style)
Start the engine and measure the output pressure of the fuel transfer pump using an in-line pressure gauge.
Test 2: Flow Volume Test (Diaphragm Style)
Caution: To prevent the engine from starting, disconnect the fuel shutdown wiring. Residual fuel in the injection pump may cause the engine to start.
Caution: Do not crank the starter for more than 30 seconds at a time. Doing so may result in starter damage.
Caution: Leave the shutdown solenoid disconnected for the following check.
Disconnect the output pressure line from the fuel transfer pump and run it into a container.
Measure the fuel transfer pump flow volume, while cranking the engine with the starter for 30 seconds.
Use the chart in the illustration to find the correct flow volume specification for the diaphragm fuel transfer pump.
• Draw a straight vertical line above the measured cranking RPM.
• Draw a straight horizontal line from the measured flow volume to the engine cranking RPM vertical line to find the
• Any intersection point above the required flow line indicates an acceptable flow.
• Any intersection point below the required flow line indicates unacceptable flow and a defective pump or too much line restriction.