Correct Fuel Pressure

[95SHOATX]

I measured my fule pressure today and have questions on the readings, procerude and functioanlity.

The fuel pressure reading was 40psi at idle WITH the FPR vacuum disconnected. When I turned the car off the fuel pressure went back to 0 psi. Is this normal?
When I turned the key to the on position I could hear the 2 second fuel pump noise. Sounded ok. However there was no fuel pressure reading on the gauge. Is this normal with the key in the on position. (Not running)

Thanks

 

[naval-avi8or]

Correct pressure is 38 +/- 2. As for the I dont think it is supposed to bleed off. All of the maintenance procedures have relieve the system fuel pressure and refer to the correct process to do it as one of the first steps.

 

[naval-avi8or]

BTW were did you purchase your fuel pressure tesing gauge.

 

[95SHOATX]

I purchased the gauge at Auto Zone. Yes there is a procedure for bleeding of the fuel pressure. That is why am puzzled. There was no pressure to bleed off after I performed the measurement. Maybe its normal? I am wondering if the problem may be the fuel return valve. I don't hear the tell tale sign of the rumbling from the back seat.

 

[olympic]

The pressure should not bleed off when you turn the key off. At least not for a while. Does your gauge have the valve for purging air out of the hose and gauge? Air in the gauge will screw with the reading. Does your car crank for a while before starting? If so the pressure is probably bleeding off between starts. I think there is a valve in the tank that's suppose to prevent this. It could need replacing.

 

[95SHOATX]

Yes my car does crank for awhile if I try to start right away. If I wait 2-3 seconds with the key in the on position and then start, it starts almost immediately. The gauge that I purchased has a bleed off button that you are suppose to depress after the reading. The gauge goes to 0 immediately therefore nothing to relieve. I would have also thought that when you turn the key to the on position fuel pressure would also be registered immediately, mine does not do this. One other observation, when I changed my fuel filter I would have thought there would be more pressure built up in the fuel line. Sorry for all of the questions back and forth, just want to be sure it is the fuel pressure relief valve.

 

[tomw]

If the fuel system will not hold pressure its one of three things- leaking fuel injector (s), fuel pump or fuel pressure regulator that won't hold pressure. The service manual(Helhs) has procedures for testing the components and isolating the culprit

Tom W

 

[95SHOATX]

Tom thanks for the additional information. You mention leaking fuel injectors as a possible cause. How would one go about testing for this? Is there a quick test that I can perform? I don't have a Helms manual. I do have an account with AllData but it doesn't mention test procedures for fuel injectors or the FPR.

 

[tomw]

Usually leaking injectors only SHO up on higher mileage cars. A tell tale sign is when the car starts up and a sooty cloud is seen comming from the exhaust. If dirty injectors end up being your problem, several SHO vendors offer cleaned, flow matched injectors at a reasonable price.

Tom W