BigP

Ok where to start? About 1.5 years ago, the fuel pump went out on me. I put a racetronix pump in there, and it ran fine for about 9 months. The finacee was driving the car, turned up the street and it died. I diagnosed it again and found no pressure at the rail. I dropped the tank down and found the fuel pressure regulator was blown off the hose causing the no start. Anyway, I replacd the whole fuel pump/sending unit with an aftermarket one from napa that cost about $400. So for the last 6-7 months the car has been running fine. The last 2 days, the car has been hard to start taking anywhere from 4-6 seconds of cranking time before she fires over. I hooked up my fuel pressure gauge to the schrader valve. With KOEO, fuel pressure primes to 45PSI, then drops to 0 immediately. If I crank the car, it won't fire, the gauge shows pressure building as I crank it, and once fuel pressure hits 40PSI, it fires over and runs. At idle, fuel pressure stays at 45PSI which to me seems low. Now, the pump is new, the regulator is new as well as the fuel filter. If the regulator was bad or blown off again, the car wouldnt even start. What else could I look at? Leaking injectors? How do I test them in the car or will I have to pull the rails out? Any thoughts or opinions on this are greatly appreciated. Thanks, Paul M

BigP

Sorry about the double post. I just took the car out for a drive with the fuel pressure gauge hooked up. At idle and light throttle driving, the fuel pressure stays right around the 45-47 PSI mark. When you tip in the throttle to about 1/4 to 1/2 fuel pressure drops to 35-40PSI and at WOT it sits right at 30PSI. I am not sure what the factory specs are for a factory replacement fuel pump are, but they seem kinda low to me. Also, the needle on the gauge is solid, it doesn't jump or shake around. Any thoughts??!!?!?!?!?

DrkPhx

iTrader: (15)

GM service manual calls for 55-60 psi under all operating conditions, so yours is way low.

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That symptom usually points to the regulator. Are you getting any codes?

BigP

No codes relating to the fuel system. The check engine light is constantly on with codes for the 02 sensors but that is becuase of the long tube headers and high flow cats. The last time the regulator literally blew off of the hose and the car would not start at all and I had 0PSI fuel pressure all the time so I hope that its not the regulator. Plus the fact that the whole fuel pump/sending unit/regulator are all relatively new. What about a leaking or stuck open injector? Would a bad injector allow fuel pressure to bleed off that fast after priming? I don't see any gas leaking from the car, and I don't have any gas smell from the tank or engine compartment area.

Mr Phil

Dude u have the almost exact same issue as me, I know this was 4 years ago and highly unlikely u still are on here but if you fixed it, what was your issue?

And if anyone has any insight as to the problem, here is a link to my thread

https://ls1tech.com/forums/pontiac-f...uestion-2.html

Lonnies Performance

iTrader: (16)

The aftermarket replacement pump modules typically have a regulator that is prone to failure. I see this a lot... the plastic housing distorts & bleeds off pressure.

Typically you can test this by removing/blocking the return line back to the tank & priming the pump. If it holds high pressure, then it is likely the regulator.

I am now offering a replacement regulator assembly that eliminates the o-ring seal.
These are $65 & are made from a factory new GM regulator. Let me know if interested.

Mr Phil

well the fuel pump was pulled from a working 00 ws6, regulator was just replaced 2 days ago and it was still the same issue, only 44psi at idle and it drops anytime throttle is opened up. i know my T/A is a 98 and it has its own specific fuel pump assembly but when replacing the pump only it shouldnt make a difference with how it works and primes correct? if this is the issue then i can most likely get my hands on a pump out of a 98 T/A but i dont think this is the issue

Frame-doctor

I too am tracking down a hard start issue on a '98 Trans Am. This one is a Lingenfelter Hurst edition, completely stock with less than 9K. I figured it was a bad pump and called Lingenfelter to order a new one and the guy suggested it may be the regulator instead. With both being in the tank, I'm not saving any effort doing one before the other. I was checking fuel pressure at the rail and noticed something odd. I cycle the key to prime system and it won't start. If I bleed the rail pressure and it dribbles out, it will then start, but if it squirts out high pressure, it won't start. Another question: Lingenfelter shows a Racetronix kit for 98-early 99. And a 99-02 pump only. Anyone use the upgraded kit? Is it critical?

Frame-doctor

I put a gauge on the rail and it shows 55-60psi with key cycle, 50-55 cranking, didn't drop after 30 min. Then I put a node on the #1 injector and no signal while cranking. I bypassed the security and no change. The search goes on.

Frame-doctor

After a couple hours trouble shooting and an unnecessary crank sensor, it turned out to be a bad IGN1 relay. I've never seen a bad relay act so erratically before. It started out last fall as very intermittent and became progressively worse. Hmm.