Hello everyone,

I've been putting off working on my vette for a while but I've finally been able to find some time to address some issues I've found with the car so far. One of the biggest annoyances I've been dealing with lately seems to be a low-end loss of torque/performance. It's a pretty weird symptom, it almost seems like I've lost a lot of power in the 1.5-3krpm rev ranges, and the car often has trouble downshifting on moderate throttle application. I recently had a reman. tranny (auto) put in, and I'm a little worried it might have some correlation with the VSS, which would also explain some issues I've been having with the speedometer. Anyways, about a year and a half ago I had to change out the fuel pump since the old one crapped out on me, and I replaced it with a Delphi unit. However, I've been having a sneaking suspicion that it's starting to reach the end of its lifespan...
I decided to measure the fuel pressure at the rail today and noticed the following:
About 20-30 psi on the key turned the engine off
30 psi at idle
40 psi at idle with the vacuum line off
About 40ish psi at WOT (with vacuum line on)
I held the engine at about 2k and 2.5k rpm and noticed that the fuel pressure stayed at a constant 30psi. However, if I blip the throttle, I see a quick response in fuel pressure. I was wondering if this is normal. From what I understand, if my fuel pressure is the same at idle and at 2.5k rpm, then I likely have an issue somewhere along the fuel line. Anyway, I'm likely going to do a driving test tomorrow with the fuel pressure gauge taped onto the window. I'm also going to try to ohm the injectors and see what's up with them. I'm also really worried it might be exhaust-related, specifically the cats. However, I recently passed a smog test with flying colors, so I'm hoping that's not the issue at hand. Manifolds/gaskets are hopefully next to be inspected. If anyone has any insight on the normal fuel pressures, please do tell! Thanks

 

Fuel pressure should be 42 psi with the engine running. Check to be sure there isn't a fuel leak between fuel pump and sender. If you still have a pulsator replace it with a piece of fuel hose with clamps on both ends.

 

Measured it running on the road today and normally sat around 30psi at idle/minimal throttle. Last time I recall I did replace the pulsator with a small rubber hose. I'll likely give the FSU and pump a quick check before proceeding any further. I'm 99% convinced it has something to do with the pump, though. I pray its not the fuel injectors leaking. I also noticed that when I'd turn the car off, pressure would leak out quickly and level out at 20psi.

 

If the regulator is original maybe just replace it. I replaced mine on my 96. Took it apart and the rubber was all cracked. They are not real expensive. If an injector was leaking it would not stop at 20 psi. It would continue to zero. Dan

 

Sounds like a plan to me, did you replace yours with an AC delco unit? Is it any difficulty taking off the fuel rail and getting the FPR off?

 

Yes, I used AC Delco. Bleed the pressure first. You need a special tool to remove the fuel lines (at least on a 96). The tool is very cheap. Straightforward after that (on a 96) . I did not have to take off the fuel rail.Dan

 

Did you find out what it was? My new fuel pump is giving similar psi, 30 at idle and 39 with vaccum like off, though not leaking pressure when turned off.