I'm not versed in Z EFI but I do know GM EFI very well. 30 psi at idle should be okay. The manifold vacuum is probably used to control fuel pressure at the injectors at any given rpm/load. If you gun the engine the fuel pressure should rise upwards to the 37-38 psi and then settle back down to 30 at idle again. When accelerating or cruising at high rpm's the fuel pressure is probably in the max range. A fuel pressure gauge in the cockpit would prove this. As a side note, NEVER run fuel lines into the cockpit for ANY reason! Only use an appropriate isolator! Fuel pressure dropping (it should hold for a few hours anyhow) quickly once the engine is shutdown is caused by one of three things, a bad check valve at the pump, a leaking injector, or an external leak. The last would be very obivous....

Both my Z and my 810 idle at 37psi. I believe that that is a function of a properly operating fuel pressure regulator. I'd say yours is malfunctioning.

Thanks for the help. I dont really have the money for one right now, unless someone is nice enough to give me one and I pay for shipping through paypal. :nervous:

I learn something new every day. Thanks

When the car is idling and I give it gas the pressure goes down instead of up.

Sounds like the FPR is belly up.

I just went to pick and pull (in the rain, FUN), But I grabbed up two fpr's just in case one doesnt work. One of them looks brand new and the other has jecs on it. They were free

Well I tried both of them and the same reading on the pressure. I will see if it holds pressure here in a few.

It still is not holding the pressure, I am now leaning towards a leaking injector or cold start valve, yeah:sick:

If you still have it, I would put the adjustable fpr back in and set it to 37 psi and then check the system for pressure leakdown.

I dont mean to be a dumb a--. But how do I do that pressure leakdown thing?

I dont mean to be a dumb a--. But how do I do that pressure leakdown thing?

I'm just referring to the same test you've been doing. Check the pressure while it's running and then turn it off and see if it holds. But using the adjustable regulator since from what I understood, it ran at 40 psi. Just adjust it down to the factory spec.