mrmint69

That looks like a problem. You don't want less pressure when the rpm's are the highest. Never saw one do that before. I had an FMU hooked up to add more fuel pressure under boost and it did the exact same thing, but got higher as the rpm's went up! I would say weak pump or fuel filter, but I believe you replaced the filter already.

Cerridius

Yes I replaced the fuel filter not to long ago.

ACE1252

Looks like fuel pump issues. Last time I checked mine, it was ~43psi WOT all the way til 6200rpm(my redline is 6500). Tested same way you did....with gauge taped to windshield.

canuck94z28

Yes the fuel pump may be weak/or on it,s way out.The fact that the trap speed ,60 ft. /poor throttle response are clear indications of this.Since the fuel pump is a major p.i.t.a job i would first maximize your combo first b/f doing any mods,stall(too big IMHO).I remember a similiar 94Z in gm high tech that had a 15.1 a/f ratio & high k/r.My car yrs. ago had 41 psi key on,46 w/vacumn 36 w/o.my car has very strong top-end(could be better!)& trap speed of 102-103 & 81.6 last summer in D.A of over 4000ft.I have some basic maintenance items to do on my 94 soon & will let you guys know.Hope this helps

Cerridius

So It looks like my fuel pump cant support my engine at higher RPMs huh... Do you all think this is my power problem? From what I have read the Fuel pressure is suppose to hold over 40PSI at WOT and mine drops as the RPM increases. If you all agree that the fuel pump is weak and needs replaced, I will probably do the trap door above the gas tank and have you all reccomend what fuel pump to get.

Cerridius

Also. I cleaned my MAF and throttle acceleration is ALOT smoother just driving normal. If I floor it from a stop it still takes a little to get into the rpm. I tested out my fuel pressure again and same thing. It's about 39-40 idling and driving normally but when I get on it as the RPMS increase the fuel pressure goes down.

mrmint69

I bet it is hurting and not good for the motor. You will definately start to run lean and that can be real bad. I am curious how much you gain with a proper working pump. I would think you would feel it breaking up in higher rpm's if it was to bad. The good news is you can drive it, just don't really get on it until fixed.

ACE1252

I agree. Be easy on it until you can replace the fuel pump.

Cerridius

Yup I need a new pump. Test my friends LS1 WS6 Trans am ( I know LS1 fuel pressure is higher 55-60 but same concept) and when he goes WOT his fuel pressure is a steady 55PSI no decrease like mine.

I tested my girlfriends stock 94 Z28's fuel pressure and hers at WOT is constantly at 45PSI no drop like mine.

So. I need a pump for sure, whats a pump that you all recommend? Something that is a little better than stock for what I have done to my car and a good fit with a decent price.

I plan on doing the trap door method.

lt1-xjs

It also sounds like it does have a cam to me, maybe the CC 502 or something similar. I'd recommend a tune along with the pump.

Cerridius

The PCM is already tuned somewhat, anyway to figure out if I do have a different camshaft? Like pull the valve cover and see if there is upgraded springs?

Im trying to see if my grandpa can contact the original owner... My cousin.

96 TA

I bought this racetronix pump from thunderracing and installed it using the trap door and never had a problem with it. the instructions were clear and over all easy to do. I also got the upgrades availible, i think if you got this you would be happy 1993-1997 LT1 F-Body Fuel Systems from Thunder Racing

lt1-xjs

Your cousin would be your best bet, the springs won't tell you about the cam. Something is bad wrong though, according to the dyno graph the torque and horsepower should cross at 5250 rpm and yours cross at 4300 rpm.

Cerridius

Well I dont know what else could be wrong I'll just start with the fuel pump since I know it's
Bad.

Is there kind of just a replacement pump that is a little better than normal so all I have to do is swap pumps?

Cerridius

Is there a possibility my FPR is bad instead of my fuel pump? Or do the tests that I did point straight to the fuel pump?