How to Measure Fuel Pressure
Modified on: Wed, 8 Jan, 2020 at 4:54 PM
- Refer to the service/factory manual for proper testing procedures on your vehicle
- The BlueDriver fuel pressure tester kit is compatible with gasoline engines only
- Always wear safety glasses and proper PPE while working in the engine bay of your vehicle
- Be aware of pinch points such as belts and pulleys when the engine is running
- The fuel system may be under pressure - relieve fuel pressure before connecting/removing fittings and wear all proper PPE
- When connecting/disconnecting fittings and adapters fuel may spray or spill out
- Before starting ensure you know the location of the nearest fire extinguisher
- If working indoors ensure proper ventilation
- Check your work area for potential sources of ignition before getting started
- Spilled fuel should be cleaned up and disposed of properly
- Before starting the motor ensure the vehicle is properly secured, if the vehicle uses a manual transmission ensure it is in neutral with the parking brake set and wheels chocked
- If using a test port fitting, double check to ensure you aren't accidentally connecting the tester to the air conditioning system
Testing Fuel Pressure
- Relieve fuel system pressure - refer to your factory/service manual for the proper procedure
Tip: You can remove the fuel pump relay and then run the engine until it stalls to relieve fuel pressure before connecting the tester
- Shut off the ignition
- Remove the gas cap
- Connect the fuel pressure tester
- Vehicles with test ports
- Remove the test port cap
Tip: Place the cap somewhere safe like the cupholder inside the car
- Place rags underneath the test port as some fuel may leak out when the fitting is attached
- Check that you have the proper fitting/adapter selected for your vehicle by gently screwing it on to the test port - if you feel unexpected resistance back the fitting off and try again, or try another adapter
On some vehicles you may be able to attach the hose directly, while on others you will need an intermediate adapter. If using an adapter connect it first, and then attach the tester hose.
Do not use excessive force or you may damage the threads - fittings should be hand tight.
- Vehicles with rubber fuel lines
- Place rags under the connection between the fuel line and throttle/fuel rail/etc
- Loosen the hose clamp and remove the fuel line
- Connect the fuel line to one one side of the blue tee fitting - the barb is compatible with 3/8" & 5/16" fuel hose so push it on as far as it will go
- Place the two hose clamps from the kit over the appropriate rubber hose and then connect it between the other end of the tee fitting and the vehicle
- Tighten all three hose clamps
- Connect the pressure gauge to the blue tee fitting
- Double check all fittings and survey the work area again quickly for sources of ignition
- Turn the key to the 'run' position to prime the fuel pump
Tip: A quiet work area will allow you to hear the fuel pump prime
- Check all fittings and the area underneath the car for any sign of fuel leaks. If leaks are found check all fittings and then prime the fuel pump again
- Prime the fuel pump again by starting the ignition, check the value indicated on the pressure gauge vs the spec value for your vehicle. Refer to a factory/service manual for your vehicle for the expected fuel pressure.
- Start the engine and allow it to idle
- Check all fittings and the work area underneath the car for leaks - if any are found immediately shut off the engine.
Tip: Have an assistant (wearing proper PPE) monitor the fittings and work area for leaks when starting the engine
- Check the value on the pressure gauge vs the expected pressure in your service manual
- Shut off the ignition
- Relieve fuel system pressure
- Place a rag securely around the fittings/hose and remove the tester from the vehicle
- Replace the test port cap, or vehicle fuel lines as appropriate.
- Check the fuel system for leaks by first priming the fuel then starting the motor if no leaks are found.
Tip: It may take an extra second or two before the motor starts
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