fuel pressure drop

[grumpyvette]

Last time I took the 85 out, it had a rough idle and no power on acceleration. Almost felt like it the times was off or it was misfiring. Plugs and wires and the ignition component are under a year old, and I have had about a year+ of trouble free driving in this current configuration of the ZZ4 motor.

I checked the fuel pressure at the schrader valve on the rail and it read 38PSI at key on and then steadily dropped. With the car running, I got 36-38PSI until I opened the throttle, then the needle dove to sub-30PSI numbers. When I closed the throttle, pressure returned to 36-38PSI.

I believe the pressure is supposed to be higher and I don't think it's supposed to dip as throttle is applied. Correct?

My plan is to replace the in tank pump and sock. I also have an adjustable regulator sitting in my tool box that I can install. I'll also replace the filter while I am dealing with the fuel system.

Anything else? I also like to check my thoughts before starting work.

YOUR FUEL RAIL PRESSURE is a MEASURE of RESISTANCE TO FUEL FLOW
IN a properly operating fuel system, your fuel pump should be supplying flow in sufficient quantity or volume to force the REGULATOR, to constantly BYE-PASS some flow to keep the PRESSURE OR RESISTANCE TO FUEL FLOW ENTERING THE FUEL RAILS LOW ENOUGH TO MAINTAIN about 40psi-43 PSI, as the injectors pulse duration INCREASES, the FLOW THRU THE INJECTORS INCREASES, and as a result the fuel pressure regulator should have to BYE-PASS LESS VOLUME, the fact that the pressure falls below the 40 psi where in theory the regulator has stopped bye-passing fuel , to the return line feeding back to the fuel tank, simply indicates the flow volume and resulting pressure of an effectively closed fuel pressure regulator, or a defective and most likely leaking regulator diaphragm, or leaking injector is your problem AND / OR the FUEL pump is supplying fuel flow volume at less than what the engine required, thus the flow thru the injectors exceeded the flow reaching the fuel rails. the first obvious step would be to replace the fuel filter which is located under the pass seat near the frame under the car, as that may be restricting fuel delivery volume to the fuel rails.

an adjustable fuel pressure regulator tends to help

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