No power to fuel pump in run position
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Launching!
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From: Russellville, Arkansas
No power to fuel pump in run position 2004 5.3L 4L60e DBW swap into 64 chevelle.
When i put the key in the run position I hear noise of the fuel pump for a fraction of a second trying to run then it stops. I hooked up a test light and it only lights for a split second. Until now when the key was placed in the on position I would hear it run for a full 2 seconds and then shut off until I started the engine.
I have tested the pump independent of the PCM and it works fine, and verified that the corvette FPR is also working correctly.
Anyone have any ideas what is going on?
It seems to me like the PCM is deciding that something is wrong and is turning off the fuel. Could this be a crank sensor? I was troubleshooting a problem with MAP sensor and MAF sensor codes (I suspect a vacuum leak) and suddenly this issue began.
When i put the key in the run position I hear noise of the fuel pump for a fraction of a second trying to run then it stops. I hooked up a test light and it only lights for a split second. Until now when the key was placed in the on position I would hear it run for a full 2 seconds and then shut off until I started the engine.
I have tested the pump independent of the PCM and it works fine, and verified that the corvette FPR is also working correctly.
Anyone have any ideas what is going on?
It seems to me like the PCM is deciding that something is wrong and is turning off the fuel. Could this be a crank sensor? I was troubleshooting a problem with MAP sensor and MAF sensor codes (I suspect a vacuum leak) and suddenly this issue began.
Staging Lane
Joined: Dec 2006
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From: Minneapolis
What your describing is the fuel pump prime feature that's built ini the PCM. The PCM applies 12v to the pump to put pressure on the line to fire the injector once it senses the the engines rotating via the cam and crank signal. The fact that your getting it to prime tell you your wiring's good.
The car was running? Any crank or cam sensor codes?
The car was running? Any crank or cam sensor codes?
Are you saying it isnt priming now? The PCM does put out 12v to the fuel pump relay, you are running a relay aren't you, because running it straight off the power from the PCM wont work , at least not for long.
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Launching!
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From: Russellville, Arkansas
I was getting the fuel pump prime (as it should) until now. Until now the fuel pump would run 2 seconds (and then stop) when the key was first placed in the run position. Now, the fuel pump "runs" (more like tries to run) for only a fraction of a second when the key is first placed in the run position.
I am thinking the PCM is "deciding" for some reason that it should not supply voltage for coil, injector, or fuel pump for some reason. Still troubleshooting but thought if I posted here I might get some advice to hurry up the resolution process.
I am thinking the PCM is "deciding" for some reason that it should not supply voltage for coil, injector, or fuel pump for some reason. Still troubleshooting but thought if I posted here I might get some advice to hurry up the resolution process.
Thread Starter
Launching!
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From: Russellville, Arkansas
What your describing is the fuel pump prime feature that's built ini the PCM. The PCM applies 12v to the pump to put pressure on the line to fire the injector once it senses the the engines rotating via the cam and crank signal. The fact that your getting it to prime tell you your wiring's good.
The car was running? Any crank or cam sensor codes?
The car was running? Any crank or cam sensor codes?
Thread Starter
Launching!
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From: Russellville, Arkansas
Yes I am running a fuel pump relay, which I have verified is functioning properly.
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12 Second Club
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From: 217
My question is: Do you have Pressure at the rails? Because "hearing the pump prime" is dependent on Fuel level and amount of pressure already in the rails and voltage in battery. Are you verify the relay is good by removing relay wire to pump and checking? Did you verify the Green wire from the PCM is supplying voltage with relay removed and are getting various lengths of time that voltage is supplied?
If all is good, check engine grounds, relay ground, and fuel pump ground. Corrosion build up on a swap is not uncommon if surfaces were not completely clean of paint and rust before attaching ground wires.
If all is good, check engine grounds, relay ground, and fuel pump ground. Corrosion build up on a swap is not uncommon if surfaces were not completely clean of paint and rust before attaching ground wires.
Last edited by lsxRanger94; Sep 8, 2014 at 06:06 AM.
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Launching!
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From: Russellville, Arkansas
My question is: Do you have Pressure at the rails? Because "hearing the pump prime" is dependent on Fuel level and amount of pressure already in the rails and voltage in battery. Are you verify the relay is good by removing relay wire to pump and checking? Did you verify the Green wire from the PCM is supplying voltage with relay removed and are getting various lengths of time that voltage is supplied?
If all is good, check engine grounds, relay ground, and fuel pump ground. Corrosion build up on a swap is not uncommon if surfaces were not completely clean of paint and rust before attaching ground wires.
If all is good, check engine grounds, relay ground, and fuel pump ground. Corrosion build up on a swap is not uncommon if surfaces were not completely clean of paint and rust before attaching ground wires.
Almost sounds like the driver in the PCM has fried, although I have never seen that happen, I guess there's a first time for everything. Do you have another PCM you could plug in and see if it primes? It wouldn't have to be tuned or even have the VATS programmed out since the prime feature works regardless if the VATS is in it or not. It would tell you if it's in the PCM or the wiring. But if the green fuel pump relay trigger wire isn't staying hot for the full 2 seconds, it leads me to think the PCM is at fault.
Thread Starter
Launching!
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From: Russellville, Arkansas
Update: car runs again.
I did 2 things. I removed the negative battery post for several hours and I moved the routing of the crank sensor wiring because it looked like it was up against the exhaust flange. When I inspected the wiring I could not find a burnt location on the wires so I really think it must have been the battery being off reset something in the PCM.
Now I am getting the P0101 (MAF) code immediately upon start up. But it does run and the fuel pump primes for 2 seconds now like it should.
I did 2 things. I removed the negative battery post for several hours and I moved the routing of the crank sensor wiring because it looked like it was up against the exhaust flange. When I inspected the wiring I could not find a burnt location on the wires so I really think it must have been the battery being off reset something in the PCM.
Now I am getting the P0101 (MAF) code immediately upon start up. But it does run and the fuel pump primes for 2 seconds now like it should.
12 Second Club
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From: 217
I've had an egr short out, but it killed everything: spark and fuel. PCM wouldn't connect. Replace pcm same thing. I unplugged sensors one by one until I got to the egr and it started and ran. I'd venture to say the MAF or MAf wiring is the issue and has an intermittent short. Find a known good Maf and retest if wiring is not the issue. It may do again once engine warms and goes into closed loop.
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Launching!
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From: Russellville, Arkansas
Drove it about 10 miles to evaluate. Runs great on interstate. Runs great as long as the RPM's stay above about 1500. Below that it bogs, has hesitation when given throttle and at idle it surges somewhat, however not as bad as before.
Teching In
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