Fuel tank switchover problem

[Greenie]

The truck ran fine on the front tank but when I switched over to the rear tank at 80mph the motor started bucking and the fuel filter light came on. Switched back to the front tank and the motor ran fine again. I did use the rear tank at lower speeds and it seemed to work fine. I don't think there's a fuel quality issue in the rear tank.
Any ideas?

 

[Cubey]

Disconnect the fuel lines on both sides of the valve and try blowing through it in the rear tank position. It might have trash blocking it. Aftermarket valves tell you to put filters between it and the tanks or warranty is void, due to that risk of trash damaging the valve.

So I did with my new lifetime warranty valve, with a pair of $4/each filters from AutoZone.

You must be registered for see images attach

 

[Big Bart]

Try Cubey’s idea first.

But if it happens again you probably need a new tank selector valve. The fuel tank selector valves wear out over time. They seem to get stuck in between tanks and cause issues. Not sure what style your year used. Some try used ones other buy the new small version as the big old ones are hard to find.

 

[Cubey]

Try Cubey’s idea first.

But if it happens again you probably need a new tank selector valve. The fuel tank selector valves wear out over time. They seem to get stuck in between tanks and cause issues. Not sure what style your year used. Some try used ones other buy the new small version as the big old ones are hard to find.

The new one I got was the same size and style as the old, but the connections were backwards vs the original, so I had to drill new mounting holes and mount it upside down as you see in the pic, otherwise it would have been a mess of excess hoses to go back and forth. It also needed the different pigtail spliced in. It doesn't matter that it's upside down though, it still works fine. My original one leaked badly but still operated properly.

 

[Old Goat]

Here is a YT Vid of taking apart the FSS showing what is inside it, and what his problem was.

There are also some threads here or on FTE detailing how the take one of these apart.

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EDIT:

Found one of the threads on tear down of the FSV Valve

FSV tear down.

Been quite a few discussions on FSV's lately (Fuel Selector Valve). Everyone likes pictures. Different years have different electrical circuits and connectors, but they are all basically the same. I'll try to explain each picture as best I can. If you have trouble with yours, don't be afraid to...

www.oilburners.net

another one

Fixing dual tanks. Tank switching valve - Ford Truck Enthusiasts Forums

1987 - 1996 F150 & Larger F-Series Trucks - Fixing dual tanks. Tank switching valve - Hello I'm new to this section but not the site. Im usually over in the bumpside section with my 1971 4x4 crew cab. However I had a problem with my dual tanks recently on my 1995 7.3 diesel and searched the web...

www.ford-trucks.com

One more

Tank Selector Valve Rebuild with some pics. - Ford Truck Enthusiasts Forums

1994.5 - 1997 7.3L Power Stroke Diesel - Tank Selector Valve Rebuild with some pics. - Don't know if anybody has busted one of these apart yet. I would imagine so. I took one off of my truck that wasn't switching, and decided to see if it could be fixed. Dang thing at the ford house is like...

www.ford-trucks.com

Goat

 

[Cubey]

Here is a YT Vid of taking apart the FSS showing what is inside it, and what his problem was.

There are also some threads here or on FTE detailing how the take one of these apart.

xc_hide_links_from_guests_guests_error_hide_media

Goat

Yep. I took the original apart but I couldn't find o-rings to fit it that can stand up to diesel, so I put the parts in a zip lock bag and tossed it in a box.

 

[Greenie]

Wow! Lots of good, useful information here.
Many thanks!

 

[Greenie]

If the valve is happy on one tank for now can I run it and just not try switching tanks until the valve is replaced?

 

[Cubey]

If the valve is happy on one tank for now can I run it and just not try switching tanks until the valve is replaced?

Yes, if your returned fuel is going to the same tank it's being pulled from. That's what I do on my F250. I've never tried to use the rear tank.

On my RV, I just removed the valve entirely and used blue clip on splicers with a jumper wire to activate the appropriate sending unit and plumbed to bypass it, making it a single tank setup until I replaced my badly leaking valve. It leaked worse set to rear than front but I get single digit mpg, so any fuel leaking is unwelcome. That's also why I needed the valve replaced, for more than a 100-120 mile range before having to refuel on a single tank, never going below 1/4 tank.

 

[Old Goat]

You can get all complicated and create a plumbers night mare, and go all mechanical.

Manual Selector Valves / Electric AND Mechanical fuel pumps

I've had people ask me about my fuel system, and have never started a post on it, just commented on others. So here we go; I have been running this setup for about 4 years now, and it still works perfect. I'm running a Carter P4070 electric fuel pump parallel to the stock mechanical fuel...

www.oilburners.net

Goat

 

[Cubey]

You can get all complicated and create a plumbers night mare, and go all mechanical.

Manual Selector Valves / Electric AND Mechanical fuel pumps

I've had people ask me about my fuel system, and have never started a post on it, just commented on others. So here we go; I have been running this setup for about 4 years now, and it still works perfect. I'm running a Carter P4070 electric fuel pump parallel to the stock mechanical fuel...

www.oilburners.net

Goat

It's not that bad. Just get a couple feet of both 5/16 and 3/8 fuel line and run a bypass around the valve. Leave the valve there for the sending unit function.

 

[ROCK HARVEY]

Your fuel pickup screen assembly in your tank has probably disintegrated, and part of it is clogging your valve. I would check to make sure that the valve isn’t stuck halfway, drawing fuel from your front tank and returning fuel to the rear. My front tank was overflowing out of the vent tube for exactly this reason. I bypassed the valve and am just running one tank until I get around to fixing it.

 

[Slicknik]

Good info here , don’t waist your money on a FSS from Ford (350$) like I did,

Better off fixing the one you have or converting to e-pump setup and run a 38 gallon rear tank , then you don’t have to worry about the switch on the dash either and can eliminate the mechanical fuel pump as well.

I have had 2 selector valves fail on me , lucky I was able to warranty one