Red97LT1

What should the FP readings be? Car is stock with stock fuel system. Here's what I am getting....
Ignition on,engine off 38 psi
Ignition on, car idiling 32 psi
ignition on,car idling,popping the throttle 38 psi


I have a feeling the FP is causing my Lean condition,but not sure why it would throw just a code on bank 2 and not on both sides?

I did find a leak coming from the TPS sensor gasket and Throttle body plate on top. That gasket was all shrunken up. Could that cause a leak condition?

Injuneer

Turn key to "run" (not "start") - pump should prime to at least 40psi and shut off.

After shutoff, pressure should drop slowly.

Start engine, let it idle, remove vacuum compensation line from fuel pressure regulator (plug end of line to prevent vacuum leak. Pressure should be 43.5psi. GM tolerance on this reading is 41-47psi.

Reattach vacuum line to FPR. Pressure should drop about 8-10psi below the "no vacuum" pressure with a stock or very mild cam. It will drop less with a more aggressive cam.

Tape gauge to windshield, take it out on the road, and run it up to full load (e.g. - WOT, above 5,000 RPM). Pressure should not drop below 40psi. This is the real test of fuel system capability.

The top cover on the throttle body is vented in front of the throttle blades (it is supplying filtered, MAF measured air to the PCV system. It would be a small vacuum leak when the PCV system is operating, with air bypassing the MAF sensor. But the PCM should be able to compensate for that small vacuum leak with the long term fuel corrections.

The TPS sensor should have a foam seal inside the throttle body housing, concentric with the shaft.

Red97LT1

Thanks Fred,
I'll check the things you mentioned. The TPS gasket is smushed,not sure how big of a problem that is making.

As for the throttle plate gasket,seems that it has been replaced by a paper/cardboard version instead of rubber. Could I just use some silicone around the perimeter of the plate and it be on?

Injuneer

GM sells a replacement kit including the top and bottom plate gaskets. Shoebox has the part #.

Red97LT1

Just verified it was the same part number that I found and it is. ACDelco 40-743
I'm going to check the fuel pressure tomorrow.

Bigtoyz97

With motor running with vac line off should be 43.5 is stock setting. If its an adjustable one set it to it and put vac line on and should be good, unless regulator diaphram is bad. But don't think I seen anything less than 39 psi on NA motor at WOT.

obaja

I thought pressure was supposed to stay steady when pump shuts off. If it drops slowly then then an injector is leaking and if it drops fast then the check valve in the tank fuel pump is failing? Am I wrong?

Injuneer

Ideally, pressure should hold on pump shutoff. In practice it usually does drop. The key is how quickly it drops. In the past I've looked through the factory service manuals and found the specification for allowable fuel drop, and it's something like no more than (roughly) 10 PSI drop in 5 minutes. That would be "slowly". Anything faster than that can be the result of failure of the in-pump check valve, a leaking fuel pressure regulator, leaking lines or fittings, leaking injector(s). Any problem size leak will drop the pressure very quickly, since we're dealing with a basically non-compressible liquid.