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Discussion Starter · #1 ·
Ive read most of the existing threads, but cant find a clear answer. Is there any check valves in the fuel return system on these trucks (95 F350 7.3)? I cant currently use my rear tank otherwise the returning fuel overflows my front tank. I just ordered a fuel selector from Riff Raff diesel, but dont want to put it in if that is not the problem. I can hear the valve switching from under the truck when I flip the switch? Any ideas?
 

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Nope, no check valves. Sounds like the fuel valve is just stuck on the return for the front tank.

There have been stories of owners taking the old valve apart or blowing air through it once it is off of the truck to clear the debris that is in it. Most of the junk that gets sucked up and causes it to stick is the pickup foot in the tank once it starts to come apart.

When it is completely off of the fuel pickup line you will run out of fuel in that tank when it hits around 1/4 of a tank. since the tube doesn't extend any further.
 

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Discussion Starter · #3 ·
OK.....Thinking about just replacing the valve and throwing an inline filter pre-valve to catch future plastic shrapnel. Dont have the time to drop the tank....see any issue with that?
 

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No real problem, but if it is the foot coming apart you will start to run out of gas in that tank at around 1/4 until you replace the foot or extend the fuel line.
 
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Discussion Starter · #5 ·
No real problem, but if it is the foot coming apart you will start to run out of gas in that tank at around 1/4 until you replace the foot or extend the fuel line.
Please help...Camping in the morning and my rear tank is once again filling the front tank. Since I first posted I have had the truck at the shop where they replaced my disintegrated fuel pickup feet, as well as replaced my fuel selector valve. I supplied the feet and valve, they are both FORD OEM. What now. I just picked up a new pigtail from napa to wire in to replace the one on the truck now that is connected to the fuel valve. Any reason this could be the issue? How to test? Other symptom of note is when I switch to the rear tank the E-pump slightly cavitates. Second I switch to the front tank it stops......
 

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Hopefully you cleaned/blew out all the lines and got any debris out of the tank? Something has to be restricting the flow. Maybe some stuff is jamming the new valve? Cheers!
 

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Discussion Starter · #7 ·
I know he's fished all the broken pieces he could of the pickup out of the tanks. Don't know if he's blew out the lines or not..... it's the exact same malfunction I had before. Same cavitation, same tank fill in the same tank. It's never the front tank that's the problem. Is it possible if the connector pin pigtail is bad won't get complete change of polarity? How do I check if I'm getting good signal at the connector itself?
 

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Discussion Starter · #8 ·
still dealing with this....... any thoughts?
 

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Did your mechanic do anything with the tank valve? When that valve is switched from the front to the back or the other way both the feed and return lines are switched. So if you are running on the front tank and the rear tank is overflowing then there is a problem in that valve where the front tank return is not opening up or opening very little.
 

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Discussion Starter · #10 ·
Did. We put in a brand new Motorcraft fuel selector valve from Riff Raff... it made no difference?
 

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Methinks a installation error then.

Sent from my SM-G988U using Tapatalk
 

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Discussion Starter · #12 ·
I'm going to have to find a schematic of how that all works internally for me to get my head around it. Is there any chance it's the actual connector to the valve itself? The pigtail? I asked him to fish all the junk out of the tanks replace the pick up feet with Motorcraft pickups and put in the Motorcraft valves. I supplied all the parts new from Riff Raff. Like I said same error as I had before the valve replacement. E- fuel pump cavitating from the rear tank, and rear tank fuel returning to the front tank overflowing it.
 

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I'm going to have to find a schematic of how that all works internally for me to get my head around it. Is there any chance it's the actual connector to the valve itself? The pigtail? I asked him to fish all the junk out of the tanks replace the pick up feet with Motorcraft pickups and put in the Motorcraft valves. I supplied all the parts new from Riff Raff. Like I said same error as I had before the valve replacement. E- fuel pump cavitating from the rear tank, and rear tank fuel returning to the front tank overflowing it.
I doubt it could be the wiring. Just because he said he got everything out, doesn't really mean much, imo. I physically looked inside my tanks to verify o had everything out.
Imo, your problem is within the quick connections. Mine started sucking air when I went efuel. I had to replace the orings inside of them. I wouldn't do that again, I would replace the quick connects, or the whole line with diesel rated rubber line.
Did your mechanic do anything with the tank valve? When that valve is switched from the front to the back or the other way both the feed and return lines are switched. So if you are running on the front tank and the rear tank is overflowing then there is a problem in that valve where the front tank return is not opening up or opening very little.
I always see people talking about the valve being able to do this. I took one apart to "clean it." So no way that could be possible. Would take a big failure, more than a piece of trash in the valve. Unless I was missing something visually.
(This was a factory valve. Maybe the aftermarket ones are different)

I think a more likely chance is the lines are hooked up wrong.

Sent from my SM-G988U using Tapatalk
 

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If it was me I would crawl under the drivers side of the truck and take a look at the valve and make sure that it was changed. I would also look at it to make sure that they didn't cut wires and splice things in to make a aftermarket one work.

Here is a picture of what one should look like. Notice that there are 6 fuel connectors feed and return from each tank and feed and return from the engine. Also notice that it isn't cheap.

 

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Discussion Starter · #15 ·
Just popped under there. Nothing out of whack that I see. It's definitely Ford OEM part, new. Nothing spliced.
 

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Discussion Starter · #16 ·
I doubt it could be the wiring. Just because he said he got everything out, doesn't really mean much, imo. I physically looked inside my tanks to verify o had everything out.
Imo, your problem is within the quick connections. Mine started sucking air when I went efuel. I had to replace the orings inside of them. I wouldn't do that again, I would replace the quick connects, or the whole line with diesel rated rubber line.

I always see people talking about the valve being able to do this. I took one apart to "clean it." So no way that could be possible. Would take a big failure, more than a piece of trash in the valve. Unless I was missing something visually.
(This was a factory valve. Maybe the aftermarket ones are different)

I think a more likely chance is the lines are hooked up wrong.

Sent from my SM-G988U using Tapatalk
[/QUOTE

OK well now I am confused as sh**t. I filled both tanks to the brim to help test to see if I was still overflowing the one tank. I have been running just the front tank the last couple days, and noticed the fuel level was going down slowly. I just switched between the front and the back and they are both down nearly a quarter of a tank? There is movement on the needle, the sender is working on both tanks.....Now I am pulling from both tanks at the same??? How is that possible??
 

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Discussion Starter · #17 ·
OK well now I am confused as sh**t. I filled both tanks to the brim to help test to see if I was still overflowing the one tank. I have been running just the front tank the last couple days, and noticed the fuel level was going down slowly. I just switched between the front and the back and they are both down nearly a quarter of a tank? There is movement on the needle, the sender is working on both tanks.....Now I am pulling from both tanks at the same??? How is that possible??
 

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Here are a bunch of PDF's on the selector valve you might want to look at. Not much for trouble shooting it but you may be able to see where your problem is. I would print them out then you have a hard copy to look at.

About the only way that you could be drawing from both tanks would be something jammed into the selector valve or wiring problem.
 

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Discussion Starter · #19 ·
Thanks for those. The weird thing is that the truck has not had any problems for years. Just recently started overflowing the back tank, so would wiring still be an issue?
 

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The only way that I know of that the back tank will overflow when you are running on the front tank would be if the valve has something stuck in it not allowing it to switch but switching the feed from the back to the front.

I would really have to tear into it to actually see just what is happening and why it is happening. But I would wager that the valve is the problem. I'd check with your mechanic and see if there is a warranty on the valve that he installed and get a new one.
 
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