How to Test a Fuel Injection Pressure Regulatorby Evan Becker
Bad fuel system pressure can result in difficulty starting your car, less engine power than normal or even stalling while the car is running. If you experience any of these problems, check your fuel pressure regulator to determine whether it is the source of the problem. If your vehicle is equipped with a fuel system test port, you can perform the diagnosis without visiting a mechanic.
Turn off the engine if the vehicle is running. Locate the fuel pressure test port on your vehicle's fuel rail, if so equipped, under the hood. Consult your vehicle's owner's manual for the exact location.
Remove the cap attached to the fuel system test port by twisting the cap counterclockwise until completely loosened. Attach the fuel pressure gauge by screwing the end of the hose clockwise onto the test port.
Start the engine and consult the pressure gauge, which is measured in psi. It should read about 45 to 55 psi in a standard fuel injection system; if you have a throttle body injection system, it should normally read about 14 to 18 psi. Consult your owner's manual to check the proper fuel pressure for your vehicle. It is all right if the gauge reads a couple psi off from your vehicle's ideal fuel pressure. If the fuel pressure is off by more than 5 psi from its ideal state, bring the car to a mechanic for service.
Turn off the vehicle, and locate the vacuum line attached to the fuel pump pressure regulator. Consult your owner's manual for its exact location.
Remove the vacuum line from the fuel pressure regulator by pinching the end of the line and lifting away from the regulator. Look for any fuel inside the line--the presence of any wetness is a sign that there is fuel inside the line. Under normal conditions, there should not be any fuel inside the vacuum line.
Reattach the vacuum line by fitting the end of the hose back onto the fuel pressure regulator, and start the car. Disconnect the vacuum line once more and check the fuel pressure gauge, which should increase by about 5 to 10 psi. This is because the vacuum line acts as a pressure regulator in a fuel injection system. If the gauge reading remains the same, the fuel pressure regulator is faulty and must be replaced.
- Not all vehicles have fuel system test ports. If yours is not equipped with a test port, have a mechanic test the fuel pressure.
Items you will need
- Fuel pressure gauge
- Vehicle specific owner's manual
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