Intermittent start problem 1996 Pontiac Transport 3.8?

Question

1996 Pontiac Transport has no problem starting first thing in morning;after the van is warmed up if I turn it off and try to re-start it within an hour it sounds like its out of gas.I replaced the starter,the e.g.r. valve,o2 sensor,etc. would a fuel pump sometimes work perfect and not when warm? I do not have fault codes or check engine light on,as when it starts it runs fine.Mechanic says it must be a sensor;I need my van for work,yet I cannot leave it running every time I go in a store-any ideas? Thanks for looking:)

Answer 1

Hi Lisa! This is going back a ways but I seem to remember a few Transports with that problem that were caused by a bad connection at the under body connector (I think it was located under the vehicle about where your feet would be if you were in the seat behind the driver) The terminals would get loose and then build up excessive heat and not let the power flow properly at times. They would have the same run/not run problem you are describing. Hope this helps!

Answer 2

To replace a sensor because you think it will fix something rarely works as there are too many that can cause a problem. If you have no codes stored in the PCM then it is likely that it is not a sensor. What you have to do is diagnose the problem when the symptom is active as in the motor will not start. In your case you have to be ready to check for spark outputs at the all of the plug wire ends. It has to be strong and consistent on all of them. You have to do this one at a time. You could have a heat related problems in the plug wires, ignition coils, ignition module, crank sensor, or even a cam sensor. Also check for fuel pressrue at the fuel port connection around the intake area, you need around 45-55 psi for the fuel pump to be considered good. You also should try to determine if the PCM is okay, but that is rarely an issue. If you find which is the problem you will have to determine which component or connection to one of the components is bad and that takes too much time to write about. Find which one you are losing and it will narrow it down. Good luck.

Answer 3

Most if not all "sensors" won't keep it from starting EXCEPT cam and crank sensors.

Though most likely the fuel pump is "sticking" when hot. Common for GM. If you can ( carry somehting to lay on and figure out in advance where the center or low point of the gas tank is) one time when it won't start reach under and hit the bottom of the tank HARD with with hand. If it's the pump this will usually get it to start.

You can also use a rubber mallet like a hubcap hammer but use some restraint if you using a tool.