Fuel Pump Randomly Won't Prime
10-25-2006, 07:49 PM
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Fuel Pump Randomly Won't Prime
OK, I have a little problem. This is on White1's truck (I'm truck sitting while he's playing Cabana boy in the USVI), a 2000 Silverado 6.0L / cam / FLT truck with probably about 125,000 miles. I know this truck very well, I was there every step of the way with the major modifications an this is not normal.
The problem is randomly the fuel pump won't prime when the ignition is turned on and of course won't start. It's done it twice now in a weeks time. The first time it fixed itself after a friend towed it back to my house and I was unable to diagnose, the second time I was able to try some things. This time I was at home and as soon as it wouldn't start I grabbed my laptop and hooked up HP Tuners. I went to the Scanner and in VCM controls there's an option to manually control the fuel pump... I turned the key on, no prime, started the scan, went to the controls and manually turned on the pump and it worked. I turned the key to "start" and it fired right off. I pressed the "on" button again, which cancelled the manual on (and returns the truck to do it's own thing) and the truck continued running. After I shut the truck off and cycled the key back on the pump primes like normal and starts like normal. Of course it's great that it starts, but the question is why wasn't the pump coming on? and when will it randomly not work again.
So: what tells the fuel pump to prime? is there a pressure sensor on the pump that could be stuck, making the truck think it has sufficent pressure? Being that I can manually turn on the pump tells me that the pump is good along with the wiring from the PCM to the pump, so what else is there?
The problem is randomly the fuel pump won't prime when the ignition is turned on and of course won't start. It's done it twice now in a weeks time. The first time it fixed itself after a friend towed it back to my house and I was unable to diagnose, the second time I was able to try some things. This time I was at home and as soon as it wouldn't start I grabbed my laptop and hooked up HP Tuners. I went to the Scanner and in VCM controls there's an option to manually control the fuel pump... I turned the key on, no prime, started the scan, went to the controls and manually turned on the pump and it worked. I turned the key to "start" and it fired right off. I pressed the "on" button again, which cancelled the manual on (and returns the truck to do it's own thing) and the truck continued running. After I shut the truck off and cycled the key back on the pump primes like normal and starts like normal. Of course it's great that it starts, but the question is why wasn't the pump coming on? and when will it randomly not work again.
So: what tells the fuel pump to prime? is there a pressure sensor on the pump that could be stuck, making the truck think it has sufficent pressure? Being that I can manually turn on the pump tells me that the pump is good along with the wiring from the PCM to the pump, so what else is there?
10-25-2006, 08:23 PM
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I think it primes up every time the key is turned on, no matter what. That sounds very strange though. It doesnt sound too much like a wire or relay problem..
I have no clue bro.
I have no clue bro.
10-26-2006, 07:48 AM
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Originally Posted by CHEVY6000VHO
I would give the fuel pump relay a change first. It doesn't sound like the actual fuel pump.
Jim
Jim
My money's on the tune. Reflash the PCM. Something's qwerky.
10-26-2006, 08:00 AM
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Originally Posted by CHEVY6000VHO
I would give the fuel pump relay a change first. It doesn't sound like the actual fuel pump.
Jim
Jim
I of course know that it's supposed to prime every time you turn the key "on", the problem is - it does it when it feels like it.
10-26-2006, 12:25 PM
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It will not prime every time the key is on.... If you prime it , turn the key off, and turn it right back on, it will not come on. It sounds to me the fuel pump is going out in it. Especially if it wouldnt start and after you had it towed home it fired right up. We see that alot here at the stealership..... people cry about no start get it towed up here and soon as it gets here it fires right up...
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10-26-2006, 01:21 PM
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It should prime every time you get in it after it's been sitting, the first time it did this it had sat for 2 hours, the second time it had set for almost 24 hours.
....but I think you missed something key: when I take HP Tuners and command the fuel pump on, it turns right on.... from a dealership standpoint that's like commanding it on from a Tech-II. With that known, the pump is good - it comes on when I know for a fact that it is getting the signal to turn on, I think it isn't being told to turn on. after I command it on it comes on and starts fine. turn off key, it continues to come on, prime and start just fine for a random amount of time without being commanded.
....but I think you missed something key: when I take HP Tuners and command the fuel pump on, it turns right on.... from a dealership standpoint that's like commanding it on from a Tech-II. With that known, the pump is good - it comes on when I know for a fact that it is getting the signal to turn on, I think it isn't being told to turn on. after I command it on it comes on and starts fine. turn off key, it continues to come on, prime and start just fine for a random amount of time without being commanded.
10-26-2006, 04:50 PM
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Well, my only other option would have been the fuel pressure regulator, but I assume your not hearing the pump wine everytime you key on the ignition.
So there are no issues after the truck is started as well?
I wonder if the is a type of control module for the fuel pump?
Kind of like a BCM (Body Control Module).
Just spitting out some possibilities........
Jim
So there are no issues after the truck is started as well?
I wonder if the is a type of control module for the fuel pump?
Kind of like a BCM (Body Control Module).
Just spitting out some possibilities........
Jim
10-26-2006, 04:54 PM
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You aint got my **** fixed yet??? 
It did it a couple of times in the past, get ready to leave somewhere it wouldnt start. Wait a few minuites and it would. it was pretty regular though. I changed my fuel filter and it quit till the day before I blew my last tranny (about a week after I cahnged the filter) then only did it one other time, but it was a loose fuse I think. I got in my truck and went to start it and the radar detector didnt come on. I played with the fuses and heard my fuel pump prime and it cranked right up. That was a few months ago. Now I leave and it doesnt get to play as much, so its being an *** to Nick. Orrrrr Nicks too hard on it and it wants a break.
It did it a couple of times in the past, get ready to leave somewhere it wouldnt start. Wait a few minuites and it would. it was pretty regular though. I changed my fuel filter and it quit till the day before I blew my last tranny (about a week after I cahnged the filter) then only did it one other time, but it was a loose fuse I think. I got in my truck and went to start it and the radar detector didnt come on. I played with the fuses and heard my fuel pump prime and it cranked right up. That was a few months ago. Now I leave and it doesnt get to play as much, so its being an *** to Nick. Orrrrr Nicks too hard on it and it wants a break.