How to Test a Fuel Pump in Vehicles

by Contributing WriterUpdated June 12, 2017

The fuel pump on a Vehicles is responsible Vehicles getting the gasoline out of the gas tank and sending it to the engine. If the fuel pump fails, then the engine won't be able to function correctly, and won't run. But before you remove the old fuel pump, it's best to first find out if the fuel pump is actually the problem, or if it's something else. To do so, you need to test the fuel pump, which can be done in under an hour.

Under The Hood:

 How to Test a Fuel Pump in a 1999 Ford Mustang

Place wedge-shaped wheel chocks behind and in front of the front wheels of the Mustang. Kick the wheel chocks with your heel to force them securely against the tire, preventing the car from rolling.

Raise the rear wheels of the car off the ground using a floor jack placed under the center of the (differential) housing in the rear of the car. Place jack stands under both rear axle tubes that connect the rear wheels to the differential. Lower the jack until the axle tubes are resting on the stands.

Attach the battery clips on the automotive circuit tester to the Mustang's battery located in the driver-side front of the engine compartment. To do this, squeeze the insulated portion of the clip to spread its spring loaded metal jaws and slip the open jaws over the battery terminal. Release the clip.

Turn the ignition key to the "RUN" position and test the fuel pump fuse in the under-hood fuse block by touching the long, sharply pointed probe end of the tester to the tiny metal test pins visible on the exposed numbered end of the fuse, protruding from the fuse block. Replace the fuse if the red light on the tester comes on indicating power is present on one test pin and the green light on the tester comes on indicating ground is present on the other test pin.

Push the probe end of the tester into the back of the fuel pump's electrical connector in the cavity that contains the pink wire with a black stripe, so that the probe makes contact with the metal terminals inside the electrical connector. In the 1999 Mustang the electrical connector is under the car, in front of the fuel tank, near the fuel lines. Have a helper turn the key to the "START" position and observe the tester. Power will show by the red light on the tester.

Replace the fuel pump driver module if power is not present.

Relieve the residual fuel pressure in the system by removing the fuel pump fuse from the under-hood fuse block and starting the engine. The fuel pump fuse can be pulled out of the fuse block with a fuse puller or a small pair of needle-nose pliers but care should be taken not to crush the plastic fuse. Start the engine and allow the Mustang to idle until the engine stalls indicating the fuel pressure has been relieved.

Screw the metal end of the fuel pressure tester's hose clockwise onto the threaded test port found on the fuel rail (sometimes called a fuel manifold) that is attached to the top of the fuel injectors that are located on the intake manifold between the cylinder heads. In the 1999 Mustang the threaded test port is located on the passenger side of the fuel rail near the front of the engine.

Reinstall the fuel pump fuse by pushing it securely into the slot it came out of. Have a helper cycle the ignition key off and one three times and then try to start the engine. This will turn the fuel pump on and prime the fuel system. Observe the needle on the gauge face and note the pressure indicated by the needle's position on the gauge face's numbered scale. If the pressure is below 45 psi, replace the fuel pump assembly.

Items you will need

  • Wheel chocks

  • Floor jack

  • Jack stands

  • Fuel pressure tester

  • Automotive circuit tester

 How to Test the Fuel Pump in the Kawasaki Ninja ZX-6R

Verifying Fuel Flow and Pressure

Remove the seats from your ZX-6R, using the ignition key. Charge the motorcycle's battery with an automatic battery charger, then disconnect the battery charger.

Unscrew the bolts at the front of the gas tank -- between the tank and the handlebars -- and the bolts on either side of the gas tank, with a 6 mm Allen wrench. Loosen the pivot bolt's nut, which is located on the bottom of the tank near the motorcycle's front seat rails, using a 10 mm combination wrench. Lift the front of the gas tank upward on its pivot bolt and prop it into place with a wooden dowel.

Reach under the gas tank and pull the fuel hose off the fuel pump's outlet, positioned directly beneath the gas tank. Push a short length of soft plastic tubing over the fuel pump's outlet, then attach a pressure gauge to the tubing. Attach another length of tubing to the free end of the pressure gauge, and place the other end of the tubing into a plastic measuring cup.

Set the kill switch on the right handlebar to the "Run" position and turn on the ignition switch. Watch the pressure gauge and listen for a 3-second-long, high-pitched hum, indicating that the fuel pump is operating. If the pressure gauge indicates a fuel pressure reading less than 43 psi for 2003 and newer fuel-injected ZX-6R models, or 1.2 psi on 2002 and earlier carbureted models, the fuel pump is defective and must be replaced. Turn the off the ignition switch.

Take note of the amount of gasoline discharged from the fuel pump into your measuring cup. The fuel pump should have filled the measuring cup with a minimum of 2.27 ounces of gasoline. If the discharge is less than 2.27 ounces, the fuel pump is failing and will need to be replaced.

Drain any fuel remaining in the plastic tubing into your measuring cup, then pull the pressure gauge and the tubing off of the fuel pump's outlet. Reconnect the motorcycle's fuel hose to the fuel pump's outlet.

Lower the gas tank onto the motorcycle's frame and screw its mounting bolts into place with a 6 mm Allen wrench. Tighten the gas tank's bolts to 32 foot-pounds with a torque wrench.

Reinstall the motorcycle's seats.

Electrical Testing

Remove the seats from your ZX-64 with the ignition key and charge the battery completely, using an automatic battery charger. Disconnect the battery charger before continuing.

Follow the fuel pump's wiring lead to its connector, positioned near the motorcycle's ECU control box between or along the side of the front seat rails. Do not disconnect the fuel pump from the motorcycle's wiring harness.

Set your multimeter to read a 25 Volt direct current (DC) scale. Push the tip of the multimeter's red positive (+) probe into the yellow-and-red lead at the back of the pump's connector. Push the black negative (-) lead into the black-and-white lead.

Set the motorcycle's kill switch to the "Run" position and turn on the ignition switch. Observe the multimeter for a sudden 12 volt reading, which should drop back to 0 volts after three seconds. If the voltage reading remains at 0 volts, replace the fuel pump relay. Replace the fuel pump itself if the pump refuses to operate with the right voltage reading.

Turn the ignition switch off and remove the multimeter's probes from the fuel pump's connector. Reinstall the seats onto the motorcycle.

Items you will need

  • Battery charger

  • 6 mm Allen wrench

  • Plastic tubing

  • Pressure gauge

  • Plastic measuring up

  • Torque wrench

  • Multimeter

 How to Test the Fuel Pump on a 2001 Chevy Suburban

Park the Suburban in a quiet area. Put the key in the ignition and turn it to the "ON" position. Listen for the whirring sound coming from the rear driver's side of the SUV. It will turn on for around 2-5 seconds, and is clearly audible without the engine running. If you don't hear it, then the fuel pump may be bad. If you do hear it, proceed to the next step.

Open the gas door and remove the gas cap. Push open the spring loaded door that's inside of the fuel neck with your hand. Have your assistant turn the key to the "ON" position and listen for the fuel pump. If you hear it, proceed forward and if not, then the fuel pump may have failed.

Pop the hood and open the fuse box located on the driver's side of the fender well. Test the fuel pump fuse using a test light, and make sure that there is current going across the fuse. If the fuse is blown, replace it with one of the same size and amperage rating. If the fuse is fine, proceed to the next step.

Locate the fuel port on the passenger side of the engine, directly underneath the upper engine cover. Connect the fuel pressure gauge to the port using your hands. Note the pressure with a pencil and paper.

Have your assistant start the Suburban and check the gauge. It should read consistently between 3-10 PSI below the result found in step 4. If not, or if the pressure varies wildly, then the fuel pump is most likely bad and needs to be replaced.

Items you will need

  • Fuel pressure gauge

  • Assistant

  • 12-volt test light

  • Pencil

  • Paper

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