Testing fuel pressure

That is correct. You need to relieve system pressure and connect the pressure gauge to the fuel rail with a T, 2 sections of EFI fuel hose and EFI hose clamps. These should be included with the correct type of fuel gauge.

Once the gauge is installed, repressurize the system, check for fuel leaks, and read the gauge.

It certainly could. The clogging of the fuel filter puts increasing back pressure on the pump.

Thanks for the information. Except I need to know if I should take a reading with the engine running?

What I did was disconnect the hose leading to the fuel filter. I then connected the gauge to the end of the filter. I turn the ignition switch on. The pump ran a few seconds. The pressure was ~50psi. Turned switch on then back on again. Pressure went ~80psi.

I feel that the high pressure is because the gauge is blocking the flow. If the gauge was connected using a "T" then the injectors firing would relive the pressure.

Again the manual is not clear about what it means to pressuring the system. If this done with the engine turned off or running.

Thanks for the time to help me with this.

Randy

That is correct. You need to relieve system pressure and connect the pressure gauge to the fuel rail with a T, 2 sections of EFI fuel hose and EFI hose clamps. These should be included with the correct type of fuel gauge.

Once the gauge is installed, repressurize the system, check for fuel leaks, and read the gauge.

It certainly could. The clogging of the fuel filter puts increasing back pressure on the pump.

I think I've found part of the answer. The book list two test. One is for the system and one for the fuel pump pressure check. By putting the gauge on the end of the hose I was doing the fuel pump pressure check. My reading of ~80psi was okay.

I now need to check the system. I will get a "T" and do this except how do I pressurize the system. After connecting the "T", is turning the swith on a couple of time to run the fuel pump enough? Or do I need to crank the motor?

Randy

This is sometimes called 'dead head' pressure and really only tests the maximum amount the fuel pump can produce. It does not in any way reflect system pressure.

It's not the injector firing that relieves the pressure. It's the fuel pressure regulator, which maintains/controls system pressure.

Both.

The spec for engine running will be lower as manifold pressure will be acting on the fuel pressure regulator. This is done to maintain correct pressure drop with changes in manifold pressure.

You could do either. But I would cycle the key first and check for fuel leaks first. Remember to check the pressure Key On Engine Off (KOEO) and engine running (KOER).

Thanks to everyone especially user saeengineer. I've learned alot about fuel injection from this experience. I connected my gauge to my rail and with the motor running read about 39psi. I then disconnected the vaccuum hose to my regulator. The psi jumped upto about 45psi.

Looks good so far.

Drove the car around the block with the gauge attached and positioned on my windshield. When the initial problem of surging/missing occured the gauge stayed consistent. So I do not feel the problem is in the pressure. Also the symptoms do not indicate an injected problem. Ford mechanic from down the street said check for vaccum leak first. So I'm in the process to replacing hoses and verifying no leaks.

Will keep the group posted on my results.

Thanks again.

This is sometimes called 'dead head' pressure and really only tests the maximum amount the fuel pump can produce. It does not in any way reflect system pressure.

It's not the injector firing that relieves the pressure. It's the fuel pressure regulator, which maintains/controls system pressure.

Both.

The spec for engine running will be lower as manifold pressure will be acting on the fuel pressure regulator. This is done to maintain correct pressure drop with changes in manifold pressure.

Sounds good to me.

I don't recall you giving any vehicle symptoms.

If you post back with them, I'll try to give you some ideas.

Please do.

No problem.