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This morning I tried to remote start my truck as I do every morning. Sometimes it takes two times for the alarm to start the truck because it doesn’t crank it long enough. I heard it try the third time without it starting. I went out and turned the remote start option off and tried to start it with a key. It just keeps cranking but doesn’t attempt to start.
I waited a few minutes thinking maybe the alarm system locked it out for some reason and tried and it still doesn’t start. I can hear the fuel pump priming each time I turn the key on. Now I know to check for spark and fuel. I will do that as soon as I get home. Lets just assume that it is getting spark and fuel. What would my next steps be? The truck has the 5.7 in it with a distributor ignition.
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[quote=”college man” post=55818]here is another test with the fuel gauge hooked up.
pinch off the fuel return line with the truck running.
the fuel pressure should jump up.also your gauge should
not drop to zero immediately. It should hold for more
than 5 min. next lets jumper the fuel pressure oil switch
orange and grey wires. see if the truck runs any better.http://www.justanswer.com/gmc/6be2k-gmc-suburban-2500-2wd-1994-gmc-suburban-tbi.html%5B/quote%5D
Ok college man here is the results of the test. I started the truck and let it run and then hooked up both injectors. The pressure was reading around 12-13. I found the other line which runs up to the engine that did not have the fuel filter attached to it. I pinched this line off with a rag and pliers. This caused the engine to sputter a little and the fuel pressure gauge jumped up to around 20 I believe.
Not sure why the gauge goes to zero after the pump stops running.
I unplugged the oil pressure sensor pigtail. I stuck a paperclip in the pigtail from the red and grey wires jumpering them together. Once the connection was made, I heard the fuel pump start running constantly even though the key was turned off. I tried to start the truck with both of the injectors plugged in and the jumper still in place. The truck started and ran normally at this point. I shut the truck off and repeated the test several times to make sure it would still start with both injectors plugged in. It did start every time. Not sure what this means at this point.
I just went back out and hooked he oil pressure pigtail up to the sensor like normal without the jumper in place. The truck is actually starting on its own without the jumper in place. Going off the flow chart you posted, I let the engine idle with the oil pressure sensor hooked up. I unplugged the fuel pump relay with the engine running and the engine immediately died. From what I understand the oil pressure is supposed to take over in case the relay dies. So does that mean my oil pressure sensor is failing and the cause of all my troubles? It is strange but the engine is starting almost like normal now although there is a little hesitation when it first starts up
ever since I did the thing jumping the two leads of the oil pressure switch together the truck has been starting almost normally with only a small amount of hesitation. This sure is strange
Well I replaced the oil pressure sensor. It didn’t seem to change anything, although the car is still starting on its own. Gonna test drive it tonight. No idea what to think
I think the oil pressure/fuel unit or wiring is the issue.
with the fuel pump hooked up. key on engine off pinch the
return line again. see if the pump pressure bleeds off. if
it does then the check valve in the fuel pump is not holding.
Also get yourself a weather tight inline fuse to replace that
fuseable link. if the hard starting/no start happens again.jumper
that switch. If the truck comes to life you now know where the problem
lies. keep us posted on your progress 🙂I clamped off the fuel return line and the pressure tester maintains pressure even when the pump stops running. So what could this mean? I guess the check valve isn’t bad. I took the truck for a test drive and it did good. I just hate when problems fix themselves because I don’t know if the problem really is fixed or not. Hate to have it die on me again. I did replace the oil pressure sensor. The engine does die when I unplug the fuel pump relay when its running. From what I understand of that flow chart, the engine is supposed to keep running if you unplug the fuel pump relay as the oil pressure sensor takes over. Not sure if this will be an issue or not. Drove the truck to work this morning and its running normally.
I have found another thread on a different website where the guy describes exactly what mine is doing with building 12-13 psi of pressure and releasing it as soon as the pump stops. He updated the thread where a couple people said TBI have a built in pressure release. Does this sound correct to you? Here is the link. http://coloradok5.com/forums/showthread.php?t=163275
If the pump held pressure with the return clamped off.
Then the check valve in the fuel pump is good and the injectors
don’t leak. The pressure regulator may be leaking. For now we got
you up and going. Thats a plus in my book. 🙂I just had a feeling I would be back here again. Almost one full week since it started working again and its back to no starting. Same issue. Flooding itself out. I did replace the oil pressure sensor and fuel pump relay last time so they are new. I tried unplugging the oil pressure sensor pigtail and jumpering the wires to get the fuel pump to constantly run like we did last time and this time is made no difference. The car didn’t magically start working after I did this like last time. I unplugged one of the injectors and once again the truck tries to start, however this time I wasn’t able to get it to run.
So here we go again. How disheartening is this although I can’t say I didn’t expect it to pop up again.
I know I just replaced the coolant pressure sensor on top of the intake but lots of stuff points to that. Is there a way to test this? I read if the sensor is bad it could make the ECM think the engine temp is -26 degrees and flood the engine with fuel to try and get it to start. Also what about the throttle position sensor? Is there a way to test that?
I think I got the problem figured out. I replaced the fuel pressure regulator and that still didn’t fix it, but I had the engine running and I accidentally bumped the wire that goes to the coolant temperature sensor and I noticed the engine idle changed when I did it. Further wiggling and I could get the engine idle to change as I moved the wires. I also noticed that the oil pressure gauge would fluctuate when I jiggled the wires to it. So, I replaced both the oil pressure sensor and coolant temperature sensor pigtails and so far so good. Also I am now able to unplug the fuel pump relay with the truck running and the oil pressure sensor keeps it running. Last time I thought I had this fixed when replacing the oil pressure sensor, it would still die when I unplugged the fuel relay. So it seems like the problem was a combination of bad connections at the coolant temp sensor and the oil pressure switch. Thanks again to everyone who tried to help.
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