To test a vehicle's fuel pressure regulators, connect the fuel pressure gauge to the fuel rail and start the engine with the vacuum line detached, and then attach the vacuum line and observe the drop in pressure on the gauge. If the fuel pressure drops around 5 lbs. per square inch, then the pressure regulators are working.Continue Reading
If the fuel pressure regulators within a vehicle are not working properly, the vehicle will not start easily and the motor will lose power or stall as the vehicle is running. It is important to regularly check the pressure regulators to ensure that the motor is running smoothly.
Make sure that the vehicle's engine is not running. Take the cap off of the fuel system test port and screw on the fuel pressure gauge.
The vacuum line on the fuel regulator can be removed by hand by pinching the end of the hose and pulling away from the engine.
Turn on the engine while the vacuum is detached. The gauge should read somewhere between 35 and 45 lbs. per square inch. Reconnect the vacuum line, and if the pounds per square inch drop by about 5 lbs., then the fuel pressure regulators are working properly.