Fuel Pumps

[ratrodder]

have you guys had any experince with intermentent fuel pump problems ?(car warm setting for an hour so-not starting or will start and spuders then clears up) car runs great when running, here is where I am at -half a tank of gas) fuel pressure reads alittle over 40lbs not running and holds for say half hour, 32lbs running, I have replaced the 3x and 24x crank sensors, checked my wireing,grounds ect. new computer, icm, coils test good, , is there any check valves or anything to look at if and when I drop the fuel tank, only does it after it sets and dosent want to idle till it warms up (new tps), any imput is greatly appreciated, thanks

[HayesPerformance]

To be honest there are a several things it could be.

Is your check engine light on?

[Sonyman]

Strange you mentioned that. At this very moment i have that problem but not for long. Thing is i went through all the major checks in the fuel system only to find out the wire harness leading to the fuel sending unit is faulty. I got it from a salvage yard. While running, if i give it a little twist, i can hear the pitch of the fuel pump change causing the car to stutter and starve for fuel but when i let go it comes back to life. im getting a new one today.

[ratrodder]

no, lights do come on when trying to start, security light comes on once in awhile, I'm thinking it not the security stuff because it will start and spudder

[ratrodder]

after the new ecm it would flash then go out, there is likely a code stored but have no way of retreiving it without takeing it somewhere , the car is a 95 GTP

[ratrodder]

thanks sonyman, I have had the car on jackstands running and checked the engine harness the same way, its as something is getting heat sinked by just setting, would think it would be a hard part, odd problem, thanks for the replys any other ideas are greatly appreciated

[HayesPerformance]

The harness to the fuel pump is a common fault on many vehicles. On my own vehicles I always upgrade the wires to the fuel pump from the factory 20-18ga wires to 12ga wires. The pump works a million times better...

I'm not saying that it is problem you have.

It could be one of the many things it could be, Its just hard to know whats wrong without being there to test things...

[HayesPerformance]

I could be a few things by the way.

Any Vacuum leaks?

Check the basics too, compression, engine vacuum, etc.

I would start with a new set of plugs, wires, replace the fuel filter, etc

Put a new 02 sensor if it is old...

If its been a while since you had a tune up, start with a engine that has been tuned up.

After this then see where your siting at...

[ratrodder]

tried to diagnos it yesterday, drove about twenty miles, went to the shop, started everytime without a hicup, let it set ,starts, drove another 15 miles all the time hot or running temperture, started everytime, never turned it off till I got to the shop with a fuel pressure guage on it ,looked at the fuel pump wires nothing(minus dropping the tank) have not put a oxygen sensor on it yet, idle on cold starts does not go up, tps is not working( new tps) 5 volts at the sensor, maybe oxygen sensor not kicking on the tps ? can here the idle air control trying to adjust idle, car runs well with the exception of the idle and hot start problem, thanks for the replys

[robertisaar]

i'm not entirely sure what you said there, but the oxygen sensor and TPS are not in any way connected to each other.

[ratrodder]

maybe not getting a read that its running rich?

[robertisaar]

maybe not getting a read that its running rich?

the TPS is an issue that is probably related to your fueling issue(and you should get fixed ASAP). but you're still confusing me with that last post, what do you mean by that?

[ratrodder]

you think the computer would try to correct the engine from stalling? running rich ?, the pump holds 32lbs steady while running, I understand the tps is crucel in telling the car where the throttle blade is, in reality you shouldnt even have to touch the throttle to start? do you know what the values should be at the other 2 wires for the tps?

[robertisaar]

the PCM will attempt to prevent a stall, but not by running rich, it opens up the IAC(and advancing spark a little) as fast as it can until a certain point, after that it says, screw it i don't care if you die, and it does just that.

and what do you mean by not touching the throttle to start? you shouldn't touch the throttle while attempting to get it to start(not with a fuel injected vehicle).

as for what the other values should be:

the PCM sends 5 volts into the TPS and depending on how far open the throttle is, you'll get anywhere from ~.5 to ~4.5Volts.

.5 being idle
4.5 being wide open.

the third wire is a ground.

[robertisaar]

your gray wire should have 5 volts on it at all times the key is rolled forward, the blue wire should change from .5-4.5, and obviously black is your ground.