RonsRed88

I'm diagnosing some strange idle problems and one of the things I did was put a mighty vac on the fuel pressure regulator vacuum line. When I pumped the vacuum once it very quickly went back to 0. Is this normal or is the diaphragm needing replaced? I don't have gas coming out of it when I run with the vacuum line disconnected.

I instaled an adjustable fpr about 7 years ago but reused the diaphragm.

It's an 88 L98 with 186k miles.

Ron

dogfish246

I am not completely sure but I think that it should not hold a vacuum. If the vacuum line is disconnected then it should lose all of the vacuum it built up. Maybe you have leaky injectors causing a strange idle???

383vett

If your MityVac line going to the vacuum pump is not leaking and you are losing vacuum, then the diaphram must be bad. No air should leak around the diaphram. If you take it apart, you will see how it is a sealed unit and should hold vacuum

RonsRed88

That's what I was thinking. Thanks.