How to Test a Fuel Pump With a DVOM

Electronically fuel-injected marine engines are equipped with high-pressure, electric fuel pumps. When you suspect that this fuel pump has failed, you can test the pump with a DVOM -- a digital volt-ohm meter, or multimeter -- to figure out if it is the pump that has failed or if the problem lies with a fuse, the wiring harness or the engine's electronic control module. You'll need a collaborator to cycle the engine's key switch in the earliest stage of the process

Things You'll Need

  • DVOM
  • 15-amp fuse
  • 30-amp fuse
  • 8 AWG gauge wire
  • Wire cutters
  • Wire stripper
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Instructions

    • 1

      Unplug the wiring harness from the pump’s vapor separator.

    • 2

      Turn the dial on the DVOM's face to the 20VDC range. Connect the red, positive test lead, to the terminal of the pink wire in the engine harness connector. Connect the black, negative probe, to the black-traced-with-white wire of the connector.

    • 3

      Tell your assistant to turn the ignition key switch to the “On” position and watch the DVOM’s readout. The meter will show 6 to 12 volts for a few seconds, then drop to 0 volts. If not, tell your assistant to turn the key switch “Off.”

    • 4

      Move the DVOM’s positive lead to the battery terminal’s starter relay. Tell your assistant to turn the key switch to the “On” position; the DVOM should show 6 to 12 volts for a few seconds then drop to 0 volts. If not, tell your assistant to turn the key switch to “Off” once again.

    • 5

      Inspect the fuel pump’s 15-amp fuse. If the fuse is blown, inspect the condition of the wiring and connections. Make any necessary repairs to the wiring and electrical connections.

    • 6

      Repeat steps 2, 3 and 4. If there’s still no voltage reading when the key switch is turned “On,” check the condition of the 30-amp fuse. Use the DVOM to ascertain the condition of the fuel system relay.

    • 7

      Cut a small jumper wire from 8 AWG gauge stranded copper wire with wire cutters. Strip 1/2-inch of insulation from both ends of the jumper with a wire stripper. Connect the jumper across the neutral switch on the remote shift handle and repeat steps 2, 3 and 4.

    • 8

      Replace the ECM and repeat steps 2, 3 and 4 if you still don’t get that 6- to 12-VDC reading on the DVOM, when the key switch is turned on.

    • 9

      Reconnect the wiring harness to the pump's vapor separator after you complete all testing and repairs.