Cummins 4BT – Fuel Transfer Pump – Testing

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
intersection point.
• 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.