How to Test Fuel Pump Voltage

Since the fuel pump is an integral component for the transfer of fuel throughout the engine, you should check it occasionally to ensure proper function before it causes problems. It is located at the back of the vehicle next to or in the fuel tank. It pumps fuel from the tank to the engine. The pump voltage test is important for checking the effectiveness of the fuel pump. Here’s how to perform the test.

Step 1 - Prepare the Settings

Connect the digital multimeter to the positive and negative terminals of the fuel pump. Make sure there are no broken circuits anywhere between the fuel pump and relay.

Step 2 - Switch Ignition

Insert the key into the ignition and turn on the key without starting the engine. A soft whirl sound should come from the pump indicating that it is ready to pump fuel into the engine. If the pump is functioning, find out if it is receiving enough electrical power. A deficiency in power supply may cause the digital multimeter to indicate a false voltage reading at the pump. To confirm the reading it is necessary to perform a voltage drop test.

Step 3 - Test Negative Terminals

Split the circuit into two. Have the ground phase on one side and the positive on the other. Use the jumper wire to power the fuel circuit and energize the pump. Connect the digital multimeter to the battery and the pump, both on their negative terminals. Conduct the tests using a live circuit wire. If the meter indicates a reading of more than 0.1 then this indicates a loss of voltage power. The reason for the loss could be damaged harness connectors or poor wiring.

Step 4 - Test Positive Terminals

Connect the digital multimeter to the positive terminals of the pump and the battery. Also test the output terminal of the fuel pump to see if it is functioning as expected. If the voltage drop is greater than the recommended reading of 0.1 volts then this is a confirmation that indeed the harness connectors or the wiring is faulty. You need to locate the exact location of the fault to correct the problem.

Step 5 - Testing Pump Relay

Establish the location of the fuel pump relay on the dashboard or the engine compartment. Remove the relay and have some one switch on the ignition without starting the engine. Check for voltage at the relay connector using a digital multimeter. Replace relay and Test the fuel pump connector at the back of the car and test for incoming voltage using a digital multimeter.

Step 6 - Test the Pump

Remove the fuel pump from the vehicle and put it on a flat surface. Use the jumper wires connected to the battery to test for voltage. If there is difficulty in removing the pump from the vehicle, take your battery to the back of the vehicle. Then connect your jumper wires to the battery and the fuel pump and test for voltage being very care ful not to cause sparking.