I give up, Damn Chevy. Why is it dying out?

Question

We just did an engine overhaul. Replaced all gaskets, Bought a new motor head, New distributor, Fuel Pressure regulator, new vacuum lines, new radiator, New ECU (Engine Brain), Ect...Everything was fine but recently my trans has been shifting late which came with no signs of wearing out. And now when you start the truck and let it sit, after about 3 minutes it revs up by itself and then dies out immediately following. Then it wont start for another 2 hours or so... Then everything repeats itself once it does start. Possible fuel pump issue? After it dies out and I turn the key back on I dont hear the fuel pump whining.....Give me your info and all possibilities. THX..Free points to best answerer.

1990 Chevy 1500. 4.3 V6

Two wheel Drive 1/2 ton

Answer 1

ground the motor to the frame and to the cab these grounds are important on chevy s i'll bet you didn't reconect the motor to fire wall ground.. cab insulated with rubber mounts and motor sitting on rubber mounts also check the grounds a the water inlet to the engine the ecu is grounded there also

Answer 2

Check the fluid in the trans mission make such the kick down cable is hook up to the carb, next check the module in the distributor and then check vacuum lines are install correct have u try using the old ECU to see if the new is working correct. Check the wiring on the fuel pump is the fuel regulator reading zero, have u check the pressure on fuel pump after it stall out? check the vac on the engine to see if it late with a vac gauge.

Answer 3

Could be fuel pump or it could be your fuel filter is stopping up on you. You need to go to an auto parts store and get a fuel pressure gauge to check your rail pressure with. then with it sitting and running watch the fuel pressure to see if it is dropping off on you;
CPI injection system requires 65 to 90 psi to work correctly. I would change it if the pressure is less that 75 psi. with new fuel filter. (Good fuel filter not substand after market filter)
Throttle body requires around 25 to 35 psi. Without looking I think the book says 15 to 35 psi but I have never been able to get one to run right with less than 25 psi. even at that under harder accelation they act up a little.

It can also be one of your O2 sensors shutting you down.
Check your ERG valve and make sure it isn't stopped up.
Check your engine temp sensor to make sure it isn't shutting you down wth engine over heating alarm. (Some will and some won't)

Here is one that drove me nuts.(giving the lady the benefit of the doubt here) You might want to check for. I had one SUV where the driver had somehow gotten the return fuel line kinked. by something she had run over and had kicked up under her SUV. hitting the return fuel line. I guess. Anyway fuel pressure read on the high side a little but still acting like it was starving for fuel.
(Kinking the fuel line a little is a trick used by some people to get the fuel pressure back up when a fuel pump is starting to get weak. Common problem on CPI injection systems because of the high pressure. Reason I said I am giving the lady the benefit of the doubt.
Here is a number you can call: 1=903-935-1222 it is ABC automotive in Marshall, Texas. Ask for Melissa. She is an ASE 10 master technician. If anyone can help you she can. She is good.

Answer 4

on the problem with your chevy did you put the ground from the motor to the fire wall back on if you have not done this try that it more than likely solve youre problem chevy need that ground to be there other wise it will stop running i have seen this a number of time were people put in new/rebuilt motors but forget the ground from the firewall to the motor. if this is not it try fuel pump relay under the hood if thats not it then you have a bad fuel pump this will not mess with your trans though you have a chevy have allways had bad trans try changing filter and fuild if that doesnt help then time for new one

Answer 5

Might be a fuel related problem. I don't know about the late shifting of the transmission though. Hook up a fuel pressure gauge and look up the specs. If you don't hear the fuel pump whine, then thats what it might be, find the relay and switch it around with one alike. I had a problem with similar issues except the fuel pump thing, and it ended up being my IAC (Idle air control). Best advise i can give to you is to check the easiest things first.

1) fuel pump relay
2) set up vacuum gauge and find specs
3) hook up fuel pressure gauge and find specs

Answer 6

I think it is fuel problems.when an engine revs and dies immediately that usually means it's running out of fuel.
It could be a few things.Bad fuel pump relay,or fuel pump,or fuel filter, could also be the screen in the fuel tank stoped up.
I would check the fuel pump relay first.
I Hope that solves it.

Answer 7

i am going through a problem close to yours.i had a engine change had the car for 6days and it die on me,they told me it was a crack cylinder. it was cause by overheating of the car, the machanic didnt clean out all the parts which cause a clog in my system .if you could get your car to a diagnostic center and put it on the machine to tell you whats wrong with the car,or take it back to the mechanic.

Answer 8

My V6 buick did the same thing. Replaced the crankshaft postioning sensor and all was well. Then my v6 Olds did it. Replaced the cranshaft postioning sensor and all was well. Then I bought an Explorer and no problems.

Answer 9

Need to check the Coil and the Ignition Modular.

Answer 10

I would say it is either the fuel pump or the sending unit. there is also a relay that could be bad in your tranny.