How to Test a Fuel Pump Check Valve

Written by david young
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How to Test a Fuel Pump Check Valve
A bad check valve can keep your fuel system from operating correctly. (Jupiterimages/ Images)

Fuel-injected vehicles rely on a high-pressure fuel system to deliver the proper amount of gasoline to the injectors. The high pressure is provided by an electric fuel pump that operates as long as the vehicle is running. When the engine is off, a check valve prevents pressure from escaping back through the pump, making it easier to restart the vehicle. If your vehicle is hard to start when the engine is warm, a faulty check valve could be the problem.

Skill level:

Things you need

  • Jack
  • Jack stands
  • Wheel chocks
  • Screwdrivers
  • Open-end wrenches
  • Fuel line removal tools
  • Compressed air

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  1. 1

    Park the vehicle on flat ground and set the parking brake. Chock the wheels on the end of the vehicle opposite the fuel pump. Remove the fuel pump fuse and start the vehicle. Allow the vehicle to run until it stalls. Crank the engine for five seconds to remove residual pressure from the fuel system.

  2. 2

    Raise the vehicle using a jack and support it securely on jack stands to access the fuel pump. Use a screwdriver, wrench or fuel line removal tool to disconnect the fuel line on the outlet port of the fuel pump. Beware of spraying or leaking fuel when disconnecting the fuel line.

  3. 3

    Turn the check valve in the end of the fuel pump counterclockwise with an open-end wrench until it can be removed from the pump. Blow compressed air through both ends of the check valve. Verify that air can only travel through the check valve in one direction and is completely blocked in the other direction. Replace the check valve if air can pass through it in both directions.

  4. 4

    Thread the old, or new if necessary, check valve into the pump and turn it clockwise until it's finger tight. Turn the check valve an additional 1/4 turn clockwise with an open-end wrench. Reconnect and tighten the fuel lines. Raise the vehicle with a jack, remove the jack stands and lower the vehicle to the ground. Remove the wheel chocks.

  5. 5

    Reinstall the fuel pump fuse and start the vehicle. Allow the vehicle to run until the radiator fan cycles on and off. Turn off the vehicle. Check the fuel lines for leaks and tighten any leaking connections. Wait 10 minutes and start the car. Check the fuel system for proper operation. Continue troubleshooting the fuel system if the check valve functions correctly but a problem still exists.

Tips and warnings

  • Check valves are very inexpensive. If you've already gone to the trouble of removing it for testing, it's a good idea to go ahead and replace it.
  • Check your owner's manual for the location of the fuel pump fuse.
  • Never service the fuel system in your vehicle near sparks, open flames or while smoking.
  • Wear proper eye and skin protection when working on the fuel system.

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