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Fuel tank issue

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Old 01-22-2018, 11:59 AM
mrfantasy mrfantasy is offline
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Fuel tank issue

I have an issue with my dual tanks. Im pretty sure both pumps are good. A long time ago I filled the front tank got in it to leave the pump and it wouldn't start. I drove there on that pump. So I switched to the other and drove home replaced the pump. It worked. So did the other. Well I use one pump for 6 months then use the other to keep the fuel fresh. One day I switched the other tank didn't work. I assumed the pump went bad. I left it in and just ran off the other. Well then I go get in it to go to work one day and it wont start. Flip the switch and the other one works again that wouldn't work before. Now a week ago I replaced the switch to see if that was it and nothing different happens. Still had to run off the same tank. Today on my way to work the truck shuts off driving. Try to restart sounds like no fuel. I switch tanks and now the other on works and the one I have been using doesn't. Only one tank is ever an option if the front works the back doesn't and vice versa.
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Old 01-23-2018, 09:49 AM
tnab1970 tnab1970 is offline
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What year model is the truck? this may help to diagnose the issue.
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Old 01-26-2018, 11:24 AM
mrfantasy mrfantasy is offline
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It is a 96 f250. It's doing this more often now.
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Old 01-26-2018, 12:00 PM
walmill walmill is offline
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Are you hearing the pumps come on every time?
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Old 01-26-2018, 12:44 PM
mrfantasy mrfantasy is offline
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Quote:
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Are you hearing the pumps come on every time?
front is switched on , yes. Rear switched on no. That's from sitting in the truck and the front was replaced with aftermarket and are usually louder. I get a friend to flip the switch while I listen and let you know if I can hear it from under the truck.
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Old 01-26-2018, 12:57 PM
mrfantasy mrfantasy is offline
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Front quit on me this morning after driving about a mile, almost the exact same place as last week. Flip to the back and started right up but went to pull away and it quit that fast. Switched it back to the front and started up and stayed running.
The fuel pump relay is it directly wired to each tank?
Where would the grounds be for both tanks?
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Old 01-26-2018, 04:47 PM
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subford subford is offline
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Quote:
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The fuel pump relay is it directly wired to each tank?
No. The fuel pump relay runs both fuel pumps on the same contact.
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Originally Posted by mrfantasy View Post
Where would the grounds be for both tanks?
Drivers (Left) side radiator support.


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Old 01-26-2018, 06:49 PM
mrfantasy mrfantasy is offline
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No. The fuel pump relay runs both fuel pumps on the same contact.

Drivers (Left) side radiator support.


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I see 2 wires. Is that one for each tank? Thanks for the reply

Last edited by mrfantasy; 01-26-2018 at 06:54 PM. Reason: Thank you
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Old 01-27-2018, 08:09 AM
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No, only one wire for both fuel pumps and other items at that point.
The other wire goes to the RABS Valve.
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Old 01-28-2018, 01:00 PM
mrfantasy mrfantasy is offline
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Got in the truck this morning. Before trying to start it I switched to the rear tank. Listened and heard the rear pump priming to line. Waited a few seconds and turned the key. Started up and stayed running. I haven't used the tank for a few days and checked the level of fuel in it since I last used it so I just set in the truck and left it run watching the guage. It was dropping fast enough to notice it so im Assuming for now the check valve in the front pump is bad. Im going to try to run off the rear pump as long as possible to see how fast the gas gets used up and checking the front to see if it fills up while using the rear to confirm this theory. I'll get back to let you know more. Thanks for all the replies.
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Old 01-30-2018, 12:20 AM
mrfantasy mrfantasy is offline
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Haven't replaced it yet but from what a mechanic friend shared with me and what I have learned on here, I'm going to come to the conclusion that the Check Valve in the front pump is sticking in both directions. Now I maybe wrong and it maybe the Check valve in the rear pump. but I'm going to start with the front and see how it acts. Check valves are never a good option. I also have saltwater tanks and would never depend on them in a system.
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Old 01-30-2018, 12:44 AM
mrfantasy mrfantasy is offline
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To explain my theory, let's Assume the Check valve is covered in old lacquered gas. It wouldn't take much to get it stuck. If I run on the front tank for a long period of time, the slug on it willbuild up on one end. well sooner or later that slug is going to fall back on the moving part and cause it to block the flow. then the pressure is not going to be able to start the truck.so I switch to the rear tank that I couldn't use because the slug that was on it had it stuck open which in the open position is allowing fuel to return into the front tank when the rear tank is used hench not allowing the pressure to build enough to start the truck. But after awhile the check valve gets clogged even more and the front pump wont even prime the line. That's a good thing for the rear because now it won't pump into the front tank and it will prime the line allowing the truck to start and run. That is my theory and after I replace the front pump I'll come back and let you know the results.
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