Automotive Fuel Pressure Testers

Automotive fuel pressure testers test the fuel pressure regulator and the amount of fuel compression on your vehicle. When the pressure is low, the vehicle struggles to start and accelerate. The fuel pump can fail due to four different kinds of gas pressures: acceleration, idling, residual, and ignition.

How do you connect the tester?

To test the gas pressure, connect the tester first. Here are the steps:

  • After opening the hood, find the junction block, remove it, and disconnect the labeled fuel pump fuse.
  • Start the car and let it run until it stalls. All the fuel pressure diminishes from the system. Then, turn off the car, reinsert the fuse and close the fuse box lid.
  • Open the Schrader valve on the fuel rail.
  • Place that fitting at the end of the tester hose on the Schrader valve and press on it until you hear a clicking sound. That indicates that the tester is connected.
How do you use a tester to test fuel pressure?

Now that youve connected the tester, here is how to do a compression test with it:

  • Put the key in the ignition and turn it to the "on" position, but do not start the vehicle.
  • Get the ignition pressure by looking at the psi reading on the fuel testing gauge. Compare that to the reading recommended for your vehicle. If the reading is lower by a few pounds or more, the fuel system has a problem.
  • After starting your car again and letting it run for five minutes, look at the gauge and re-check the psi reading. This time, it is the idling pressure you are looking at. Compare it to the recommended reading for your car. If the current idling pressure is a few pounds more or less than the recommended level, there is a problem with the fuel system, such as a weak fuel pump.
  • Following the re-check, find the return fuel line and use needle-nosed pliers to pinch it off.
  • Then, read the psi again. It should about double the recommended idling pressure. If not, there could be several problems with the fuel system.
  • Disengage the pliers from the return fuel hose.
  • Turn off the vehicle and remove the key from the ignition. Let the vehicle sit for about 10 minutes.
  • Check the psi reading on the gauge again. This will be the residual pressure. Compare the amount of compression loss to the amount that is acceptable to lose per the manual. If it is excessive, there is an external or internal fuel leak.
How do you remove the tester?

Once you are done testing the fuel pressure on your car or truck, youll need to disconnect the testing mechanism from the system. Here is what you do:

  • Remove the fuel pump fuse again.
  • Evacuate all the fuel compression by starting up the vehicle and allowing it to run until it stalls.
  • To disconnect the hose, pull back on the connector locking ring and pull the connector from the fuel rail.
  • Reinstall the fuse and close the under-hood junction block lid.
  • Reattach the valve cap and close the hood.