Fuel Pump Issue
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Fuel Pump Issue
I switched to the rear tank today after start up and the fuel pump runs continuously. Truck runs fine with no changes. Turn it off and restart and same thing. The front tank is fine. The truck runs great on either tank.
If I have the rear selected and turn the key on but no start, the pump will run for a second or two and turn off like it is supposed to. I have read it could be the pip causing this. I have had a new distributor in it for about 1500 miles. I have read of other things that can cause my issue, but I would like some opinions before I start replacing things I have no idea about. Thank You Sandy
If I have the rear selected and turn the key on but no start, the pump will run for a second or two and turn off like it is supposed to. I have read it could be the pip causing this. I have had a new distributor in it for about 1500 miles. I have read of other things that can cause my issue, but I would like some opinions before I start replacing things I have no idea about. Thank You Sandy
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Would the truck still run on that tank if the relay was bad? The pump turning off normally when the key is on but hasn't been turned to start seems to be a clue. I don't know. Sandy
Cargo Master
Joined: Mar 2010
Posts: 3,326
Likes: 292
From: Laramie, WY
I'm not clear on what you're saying is the problem.
"I switched to the rear tank today after start up and the fuel pump runs continuously. Truck runs fine with no changes. Turn it off and restart and same thing. The front tank is fine. The truck runs great on either tank."
Which pump runs continuously after switching to the rear? Is this during engine running?
"I switched to the rear tank today after start up and the fuel pump runs continuously. Truck runs fine with no changes. Turn it off and restart and same thing. The front tank is fine. The truck runs great on either tank."
Which pump runs continuously after switching to the rear? Is this during engine running?
Thread Starter
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
The rear tank is running continuously when I start the truck. When I turn the key on, but I don't start it, the pump will run normally for a few seconds and then the pump shuts off (like it is supposed to). Once I start the truck the pump comes back on and runs continuously.
Happy to rephrase this if it doesn't make sense. Just ask.
Sandy
Happy to rephrase this if it doesn't make sense. Just ask.
Sandy
Laughing Gas
Joined: Apr 2011
Posts: 913
Likes: 7
The rear tank is running continuously when I start the truck. When I turn the key on, but I don't start it, the pump will run normally for a few seconds and then the pump shuts off (like it is supposed to). Once I start the truck the pump comes back on and runs continuously.
Happy to rephrase this if it doesn't make sense. Just ask. Sandy
Happy to rephrase this if it doesn't make sense. Just ask.
Sandy
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
When I use the FRONT tank the pump comes on during start up but stops making the running sound after a second or two. You never hear it again. The rear used to work that way if I remember correctly. but now it is making the running sound all the time. Sandy
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Laughing Gas
Joined: Apr 2011
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How in the world would the vehicle stay running without fuel pressure. You are just not hearing the front tank pump while the vehicle is on.
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Perhaps the sound is not the pump. When you turn the key on before you start you hear the pump prime quickly and then shut off. So I guess what I am hearing is whatever makes it prime. It has always shut off and never comes on again. Now the rear is running priming or whatever is making the sound, all the time. Sandy
Laughing Gas
Joined: Apr 2011
Posts: 913
Likes: 7
Perhaps the sound is not the pump. When you turn the key on before you start you hear the pump prime quickly and then shut off. So I guess what I am hearing is whatever makes it prime. It has always shut off and never comes on again. Now the rear is running priming or whatever is making the sound, all the time. Sandy
That would be the fuel pumps. Your truck has its own fuel pump per tank. They prime on initial key turn - that is a function of the PCM, the PCM will let the pumps run for two seconds without any signal from the PIP. Once a PIP signal is received, the pump for the tank you've selected by switch will turn on.
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Right, I mentioned the PIP in my initial post. I understand what you are saying but I can hear the front pump prime and then I don't hear it again. What is confusing is that I hear the rear prime when the key is on but not started, then it stops, and then I start the truck and I hear it start running again. When I do that with the front tank I hear it prime and then stop, and I start the truck and I never hear it again like I do the rear. My hearing is not the best but I don't think it is the issue. Sandy
Laughing Gas
Joined: Apr 2011
Posts: 913
Likes: 7
Right, I mentioned the PIP in my initial post. I understand what you are saying but I can hear the front pump prime and then I don't hear it again. What is confusing is that I hear the rear prime when the key is on but not started, then it stops, and then I start the truck and I hear it start running again. When I do that with the front tank I hear it prime and then stop, and I start the truck and I never hear it again like I do the rear. My hearing is not the best but I don't think it is the issue. Sandy
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
HUH?
Must be since I have no running issues on either tank. I haven't run the rear in some time since I have been checking mileage. Guess I just don't remember the rear sounding like that. I can hear the rear from the cabin and can't hear the front while kneeling by it. Unless anyone else chimes in I will assume it is OK. Thanks for your time and patience. Sandy
Must be since I have no running issues on either tank. I haven't run the rear in some time since I have been checking mileage. Guess I just don't remember the rear sounding like that. I can hear the rear from the cabin and can't hear the front while kneeling by it. Unless anyone else chimes in I will assume it is OK. Thanks for your time and patience. Sandy
Fleet Owner
Joined: Oct 2005
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From: Kentucky
This...the fuel pump is supposed to run full time when the engine is running.
Cargo Master
Joined: Mar 2010
Posts: 3,326
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From: Laramie, WY
Okay, I understand now. There is no problem really, it's more of a question about sounds. If the rear is that loud, it could have it's own issues. I cannot hear either of my pumps running over the sound of the engine. I wouldn't do anything about it at this time myself, as it could continue to work for a long long time, but perhaps the rear pump is failing. If you're so inclined, a pressure check may confirm or refute any actual pump issues.