Fuel Problems?

[gtp3.8]

Hey folks. I wasn't sure if I should start a new thread or not but I felt that it might need to.

I have a 1997 Grand Prix GTP with a few mods. 3.4 SC pulley, reprogramed pcm, cold air intake and u bend delete. A week or so ago I started having hard starting problems like the car would crank for a few seconds sometimes before it would start. Then sometimes it would crank for a few seconds not start and I would try again in a few seconds and it would start. I noticed that it seemed to be a bit harder to start if it was hotter than usual to start. Once it got started it ran like normal. I posted a topic about starting problems and it seemed that it was a fuel pressure regulator or the fuel pump was the problem. I have changed the regulator and cleaned and checked the MAF and the IAC and I still have the same problem. I haven't changed the fuel pump yet. When I turn the switch on I hear the pump come on for a few seconds like usual so I wasn't sure if it could still be the problem. If it was the pump wouldn't I see problems while it was running? I'm not sure if there is anything else to check or it could be.

[grandprixgtx00]

what kind of plugs are you running? are you sure its a fuel problem?

[tblake]

Originally Posted by gtp3.8

.... If it was the pump wouldn't I see problems while it was running? ....

In a word, No. Its hard to explain, but as the car is running, the pump is constantly pumping fuel. Once you turn the key off, the fuel pressure should stay for a while so when you go to start your car again, there is residual pressure to start the motor. If fuel pressure immediatly drops to 0 after the key is turned off, there is no residual pressure, and the pump has to fill the lines again, thus causing a hard start. I hope that makes sense.

You need to check fuel pressure again. I'm betting fuel pressue drops immediatly to 0 after you turn the key on, and off.

You replaced the fpr, I'm still leaning towards a bad check valve on the fuel pump itself.

[richtazz]

you mentioned you cleaned the MAF, but did you try unplugging it and then starting the car to see if it runs better with it unhooked? MAF sensors can start to go bad without tripping a CEL. The common symptoms are long crank time (especially after the car is warmed up) and/or unstable idle/part throttle stumble.

[tblake]

Originally Posted by richtazz

you mentioned you cleaned the MAF, but did you try unplugging it and then starting the car to see if it runs better with it unhooked? MAF sensors can start to go bad without tripping a CEL. The common symptoms are long crank time (especially after the car is warmed up) and/or unstable idle/part throttle stumble.

Rich, he has another post where he stated that he checked fuel presure and key on it will prime to 45 and when the pump stops, the pressure immedaitly drops to 0. He replaced the fuel pressure regulator, and could definatly have multiple issues here, but I think he needs to check fuel pressure again.

[richtazz]

thanks for the heads up Tim. I suggested the MAF test simply because it takes 10 seconds to do and is free. With the fuel pressure dropping immediately to zero and a new FPR didn't fix it, I'd pull some plugs and see if you have any fuel saturated. If so, I'd suspect a leaking injector. If not, I'd suspect a bad fuel pump module.

[tblake]

No problems Rich, Sorry if I came across like an A-Hole. I didnt mean it.

Second time reading it, I think I could have worded that better.

[gtp3.8]

Thanks for all of the help everyone. The fuel pump makes a whole lot more since now that I understand about the check valve thing. Before I just couldn't get everything to add up.

[tblake]

Throw a fuel pressure guage on it one more time and check fuel pressure before you jump into the pump.

Then it might be a good idea to ohm out the injectors and pull the plugs to see if any are overly wet with fuel.

Fuel pumps are spendy, and a part I would hate to replace and then not have it correct the issue.

[richtazz]

Tim, we're good. I didn't take it that way at all. I didn't search for or read his other post, so I wasn't sure if that issue had been resolved or what had been done prior. I appreciated you letting me know, so we could shift or focus. As usual, you and I were on the same page, we just happened to be reading different paragraphs...