Fuel Pressure Regulator failed AGAIN

[Barry]

This is #3 that has failed, all due to leaking fuel back into the vacuum line and into the plenum. Am I just unlucky, or is there something causing this to happened? The fuel pumps have not been changed in the 12 years I've owned the car, which is a 1991 by the way.

[Schrade]

Welcome onto the boards there...

All the knowledgeable guys seem to have been off of the boards this summer...

It's a forgone conclusion that the diaphragm IS rupturing, if the vac supply is drawing fuel???

Any chance of a blockage / restriction in the return line? How to test for THAT I do not know - whether there's a check valve of any sort between FPR, and tank???

[Franke]

I agree with Schrade that the diaphram is rupturing. So with that said have you checked the fuel pressure coming into the regulator? With the ignition on and engine off the pressure should be 48 - 55 psi. If higher than that then are you getting any codes or exhaust odors?
According to the manual the return line goes directly back to the tank. If you have a restricted return line, fuel pressure will increase . Like Schrade says, check for a restricted return line somewhere especially any rubber fuel line connections.

[scottfab]

What mods are in the car?
Could both fuel pumps be running all the time?
Has the wiring been changed?

Each fuel pump comes with an internal over pressure release.

As others have said though. Start with blockage or smashed fuel
return line. (pressure test)

[Barry]

How do I check the fuel pressure coming in to the regulator? Any easy way to do this?

[Barry]

And to answer the other questions, there are no codes being set....no wiring mods that I'm aware of, and the only other mods to the car are after market cats and a small exhaust mod.

[Franke]

On the passenger side of the engine is a fuel rail schrader valve with a cap on it. Take the cap off and put a fuel pressure guage on it. I used an air conditioning guage set for 134a. Be careful as there could and should be fuel line pressure to bleed off before you put the guage on. Once the guage is on turn the key to on (not start). Pressure should be between 48-55 psi. With engine running pressure should drop about 5-8 psi as the regulator is doing its job. As with any job concerning fuel, care must be taken to prevent leaks of any kind so be careful. When connecting/removing the guage use some shop rags to absorb any fuel from the connection. Hope i didn't miss anything.

[scottfab]

How do I check the fuel pressure coming in to the regulator? Any easy way to do this?

Good question. I've not done this on a ZR-1.
Some ideas:
1. Remove the fuel filter temporarily and put in a "T" . Run the extra line out to a pressure gauge. (use GOOD pipe clamps)

2. Remove the fuel pump assembly and install a "T" right after the "Y" junction. Run the extra line up to a schrader valve near the opening such that you can get at it with the cap off (disadvantage in that cap must be off to measure)

Others may have better ideas. Obviously these are untested ideas so be careful !!!