starting problems

[Sinister TA]

I have a '95 Trans Am (moderately modified) and it has recently developed a problem in starting. The car will rarely start on the first attempt, but after turning it over a few times, turning the key back and then turning it over again, the car will start and runs perfect when its running. The fuel pump is still good as far as I know. The pressure tested well within in specifications. Does anyone have anythoughts on what might be the culprit??

PS. Plugs and wires are bran new.

[DeWynter]

Could be the check valve i the pump stuck. Lets the gass runn back into the tank then the pump has to pump it all the way back to the engine.

[Injuneer]

Put a fuel pressure gauge on it, and check for the symptoms described in the response above. When you turn on the key, but don't start the engine, fuel pressure should rise to the range of 41-47psi. The pump will shut off after two seconds, because the PCM knows the engine isn't running. When the pump shuts off, the system should hold the pressure, only allowing it to bleed off over a long period of time. If the pressure drops rapidly, you know you have a problem with one of three things:

-as mentioned above, the check valve in the fuel pump is faulty
-the fuel pressure regulator is leaking (check the vacuum line for fuel)
-injectors are leaking (pull the rails, pressure system, look for drips)

[Sinister TA]

fuel pressure is fine, but how would one go about checking the check valve in the pump? And what possibilities might exist for the problem in the ignition system?

[Injuneer]

fuel pressure is fine, but how would one go about checking the check valve in the pump? And what possibilities might exist for the problem in the ignition system?

If "fuel pressure is fine", why would you have to check the check valve in the pump? That would only be necessary if the system would not hold pressure in the manner I described. If "turning the key back" is what "cures" it, my first guess would have been a fuel pressure problem, because cycling the key will build pressure on a weak system. But if the fuel pressure is fine, that can't be the problem. Offhand, I can't think what part of the ignition would respond to cycling the key. Have you scanned it for codes? Might be an issue of the Opti low resolution pulse failing to set correctly in the PCM on the first try. That will shut down the fuel pump and the injectors. But it would also set DTC code 16 in the PCM for "loss of low resolution pulse", and that code would stay stored even after the PCM found the pulse after cycling the key.

Does your "security" light possibly stay on during the first startup try?

[LoudLT1]

same problem in my daily driver. (95 lumina v6) it was the starter!!!!!
ed

[Sinister TA]

the frustration i have with this problem is that there are so many things that could possibly be wrong that it is so hard to tell which is the actual culprit. I am searching for someone who has perhaps had this same problem and knows what it is.

[Injuneer]

the frustration i have with this problem is that there are so many things that could possibly be wrong that it is so hard to tell which is the actual culprit. I am searching for someone who has perhaps had this same problem and knows what it is.

Just curious... did you actually measure the fuel pressure?

[Sinister TA]

yes the fuel pressure was measured to be 45 psi with the engine off and key on. Unfortunately no one that i have called or talked to has been of much help besides asking the obvious. And if you don't mind me asking, where did you get your degree in engineering? Because I attend the University of Illinois in Mechanical Engineering.