I have a 90 chevy k1500 350 tbi with a problem! I have traced problem to... after turning on key fuel pump kicks on when u crank it over injectors shoot gas and truck starts! After few seconds injectors stop spraying and truck dies! This can happen many times over and over! Eventually sometimes truck stays running and all is great! I changed ignition module, oil pressure sending unit (which i was told controls gas after vehicle is running) fuel filter, computer, fuel pump relay, I am at a loss now! Hope this helps and hope someone can help me!
Try bypassing the oil pressure switch on the back of the block behind the distributor, if there oil pressure switch goes bad it will do this. had one that drove me nuts trying to fix it then figured out I had to buy a book and low and behold thee it was 3 wire oil pressure switch you can't see between the engine and fire wall just behind the distributor and costs 8 bucks to buy new.
Been there before!!!! usually it turns out to be something really dumb that makes you say "Why didn't I look at that first???" (either while you are smacking yourself in the head , or, just after!!!!)
Good luck again!!!
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If you have not looked here, perhaps something will give you an idea where to look. sometimes having a better understanding of what you are working with will give you an idea!!!
No, I don't give up...I know most of what's here but forgot a lot too...if I remembered everything I've learned id be in the funny farm by now (though I'm always close)
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If you have a bad fuel pump it will continually run key on engine off
and the computer will try and compensate for the lean mixture by adjusting timing advance and retard. This is when the engine surges and sometimes dies. All this is because the O2 sensor is regulating your fuel flow via the computer. check fuel pump pressure 1st, then idle air control, then fast idle circuit. Last of all is the oil pressure sensor which will kill the fuel in case of a roll over.
If you have a bad fuel pump it will continually run key on engine off
and the computer will try and compensate for the lean mixture by adjusting timing advance and ******. This is when the engine surges and sometimes dies. All this is because the O2 sensor is regulating your fuel flow via the computer. check fuel pump pressure 1st, then idle air control, then fast idle circuit. Last of all is the oil pressure sensor which will kill the fuel in case of a roll over.
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Had same problem was injecrors on start they get a higher pulse check with ohme meter dont remember the readings
I have an 89 chevy 4x4 which had the same symptoms. the temperature sensor was causing the problem . My dad also has an 89 2500 . It was doing the same thing. The mechanic could not solve the problem. I told him to change the temperature sensor.it fixed the problem . Try this, i bet it will work.
Check the egr valve also and the pvc valve
Hey farly, my truck is doing about the same thing. what was it???
I have a 94' chevy with tbi and I have replaced the distributor altogether, I was having an issue where the truck seemed like it was starving for fuel, like there was a brick wall in front of it when i was driving and it would start bucking and acting crazy, I finally traced it down to replacing the distributor and it fixed the problem, but before I had replaced that I tried several things like you had, like replacing the ignition module, the pcm, the fuel filter, even checking the fuel pressure,lol.....but little piece of info if you decide to do this go with the better distributor, i bought a reman one and I feel as though I'm not getting enough spark when it get cool out, i'm thinking of taking mine and exchaging it for a better one.
Ok, the one thing you didn't change is the pick-up coil in the distributor The ECM relies on a trigger signal from the ditributor, thats made by the pick-up, to close the pump relay and keep the pump running. The oil pressure sender can also operate the pump after it "sees" enough oil pressure, ( about 5psi I think ) thats probably why it will stay running after you start it a few times, you build enough volume/pressure at that switch to cause it to close and run the pump. try a pick-up coil, and you might be home free.
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there is no security system on the truck.
thanx for the help! i am really stuck on this one! thsi weekend im gonna run a hot wire to pump from a switch and manually turn it on to see if its a fuel pump failure or a electrical problem! I dont know what else to try! That is a good point u make though! only wierd thing is the colder it gets outside the more times it has to be started to get it to keep spraying fuel and running!
ya i wish that was issue! but i dont know what would cause fuel to stop completely after few seconds. Its wierdest problem ive ever encountered! If you think of something else let me know im open to suggestions! Besides five gallons of gas and a road flare haha!
still have no idea whats wrong please help!!
Don't forget...the older carbureted engines relied upon closing off the air flow to richen up the mixture in colder weather...on injected engines the system adds more fuel instead. If the computer does not know what the temp is, it won't do that and will either keep the fuel at running temp parameters or will keep it in "cold start" Usually though neither will cause the engine to shut down but will make run really ratty.
A real "head scratcher"...only thing I can think of is that there may be a poor connection either at the ignition switch or at the pump harness that is breaking down but eventually "spark welds" itself at times just enough to keep it running. Without the benefit of actually being there, the best I can do is guess which may or may not help. good luck though!!
sounds like a security system that has decided not to function as planned. try re-setting it.
I already got a new rotor/cap, new wires, spark plugs, fuel filter.
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