Leaking fuel tank selector valve?

Hello all,

So - after working on this truck and ironing out a fair number of issues - thanks to the help of the members of this forum - I was driving to work a couple days ago patting myself on the back for getting all the 'key' jobs done and enjoying owning a reliable vehicle.

Silly me. So recently I've been making a point to park in a clean spot on asphalt while I have been at work for nine hours a day just to do a thorough check to make sure there were no leaks etc when standing. None! For over a week! Felt good!

I did the same yesterday but this time found a spot under the driver side door. Are you kidding me?!

Checking under the truck I see fuel is dripping from the lowest point on the frame by the fuel selector valve. The top half of the valve is dry, the bottom half is wet. The biggest wet area is on the rear tank return line, but, again, this might just be a low spot. It's a surprisingly frequent drip.

Looks like I have either a leaky coupling between a fuel line and the valve, or a leaking valve itself. The lines up to the valve on each side appear dry.

I'd like to ask some questions before I embark on this - I've found going into a job well-informed by Oilburners contributors is very helpful.

I'm planning on replacing the valve, I guess. My questions:

*If I cut the fuel lines to replace the couplings to fit a new valve, am I just going to get a tank full of fuel siphoning back at me? (If so I'll be ready. Tank is almost full....)
*Is there a common area from which these valves leak? Like the female couplings themselves? Or an o-ring on the pump?
*I can't find a valve that exactly matches the current one I have. The current (leaking) valve has one each of supply and return on the top, bottom and the rear-facing end. The closest one I can find is this one (which seems to have an extra inlet/outlet, which concerns me). Other than having to wire up a new connector correctly and reroute the fuel lines a bit using fuel hose, anybody foresee any issues here? Looks like the mounting bolts should match up. That would be something at least....
*Guessing this new valve will require new couplings, correct?
*Are there any fuel pressure - or other issues - which could cause a pump to leak? In other words, should I also be looking elsewhere?

Anything else I should know before getting into this? Really need this truck working by the end of this week for a job..... Doing some research online I see that these valves are a weak link on the truck, but I can't find any direct information on the questions above.

Thanks as always.

My recommendation is to just put one of these in place of your FSV, run fuel hose to and from your tanks and engine, and forget about it.

I suggest putting this valve through the floor, between the door and the driver’s seat.


Not much fun to do, but IMO it’s worth it. I did it to my 86, haven’t to my 91 though, I will probably get to it this fall. The electric FSV in that truck still works, but the truck has 35,000 miles on it, so not much is worn out.

You have to leave the wiring plugged into your old FSV, so that your switch can read each different tank.

The brass valve is the way to go. Ford used these back in the 70`s as I remember.
Full Proof.
If you go with the pollack valve, then yeah you need to cut off the ends of the fuel lines
and splice etc... to the new valve. Probably made in China.

The market is also flooded with the exact copy of the Ford valve on Amazon and E-Bay.
One example, then it is a matter of R&R the valve.



Goat

Old Goat said:

The brass valve is the way to go. Ford used these back in the 70`s as I remember.
Full Proof.
If you go with the pollack valve, then yeah you need to cut off the ends of the fuel lines
and splice etc... to the new valve. Probably made in China.

The market is also flooded with the exact copy of the Ford valve on Amazon and E-Bay.
One example, then it is a matter of R&R the valve.

https://www.amazon.com/Selector-Valve-Super-Diesel-6C3Z9189A/dp/B07GVFCJML

Goat

Click to expand...

Thanks as always.

Brass valve. Yes, thinking of that method. Not sure I want it in the cab. But also don't want a fussy electronic fuel selector valve... But seems lots of folks like that set up.

That Amazon one a) looks like a cheap toy! and b) gets mixed reviews at best. Makes me wary either way....

While I'd prefer USA-made for various reasons, the Pollack one being possibly made in China doesn't necessarily bother me too much - my expectations based on price just need to be realistic, regardless of the country of manufacture. I have used many high quality Chinese parts over the years. And, true, some duds.... I tend to keep away from the bargain basement parts.

If I cut the lines I'm just going to have the diesel siphoning out, correct?

Thanks again.

A good bit cheaper here with free shipping too:

I did change out my FSV a few years back, and used the one with the
colored caps. Almost a direct copy of the Ford one. Who know`s, maybe
the genuine Ford one is made in China.
It did poop out a year later, pulled fuel from the rear thank and returned
to the front tank, till it over flowed.

There isn`t much to the guts of them, a little electric motor, valves that
switch between the 2 tank and connects the correct wire to what ever
tank you are using so the fuel gauge is correct.

I just run my rear tank to the engine and then the return goes to the
same tank. I have a 38 gallon one.

Here is a video showing how it works.

A thread showing how it works

With the brass valve, it is under the floor. with the the handle inside
the cab just below the drivers seat. So no fuel hoses inside the cab.


Goat.

I am a self-made professional expert when it comes to brass manual tank selector valves; I have used them for years and years and know all their strengths and weaknesses.

I strongly recommend you avoid the long ones like the link above that switch both Draw and Return and instead use two ordinary ones, one for Draw and the other for Return.

The place to mount them is like he said, through the floor, between the seat and door.

If you use the ordinary valves, they are much easier to mount to the floor as they have a mounting "ear" with two bolt-holes that you place spacers on the bolts to make the top of the actual valve against the floor.

Now, here is a huge tip that you will appreciate many times later; get the valves located and mounted through the floor; BUT, do not hook up any fuel lines yet.

Now, remove the valves; and, using the "stem" hole(s) as the pilot hole, take a hole saw and cut a big hole larger than the big nut on top of the valve, big enough that you can remove that big nut and take the entrails out of the valve from inside the cab, WITHOUT having to disconnect a bunch of fuel lines and remove the valve from the truck.

All of the brass valves have a Delrin "cone" that directs the flow of fuel --- this is the weak point; as, something about diesel fuel will make that Delrin cone seize inside the valve so tightly that you really have to get rough to get it out to clean and lubricate it.

If you followed my advice from the get-go and sawed/drilled those big holes through the floor, then you can address this without ever having to crawl under the truck.

That Delrin cone seizing is why I dislike the tall valves that switch TWO Delrin cones with a single handle on the same skinny stem; one or the other of the cones will seize and you will give the handle just wee bit too much torque in trying to get it to move and snap the stem off down inside the valve.

With two separate valves, you can better feel when you need to NOT attempt to turn the stem.

Don't worry about the big holes you cut through the floor; you are going to cover them up with a custom removable plate.

The guts inside these valves are really simple; and, once you have had one apart, you can do another with your eyes closed and blindfolded with a sack over your head.

As for the fuel gauge switching from one tank to the other, this is taken care of with a SPDT Toggle-Switch; that you can run longer wires into the cab or just mount the toggle-switch through a hole in the floor near the selector valves -- that's where mine has been for years.

I am really fond of my manual selector valves; I wouldn't have another electric valve as a gift with five big hunnert-dollar bills attached.

One more bit of advice = don't just screw a bunch of hose barbs straight into the valve and then crowd and kink the fuel lines around it.

Use some street-elbows and nipples and such to get things pointed in the right direction before connecting the fuel lines.

I highly recommend the ends of the fuel lines have Female JIC Swivels and there be Male JIC Adapters in the fuel valve ports; then, you can make up a couple "jumper" lines with JIC Males on both ends.

If a valve sticks or otherwise fails, you can quickly bypass it using your JIC "jumpers"


As for whatever you decide to do, the answer to your question is YES, you are in for a fuel bath; fuel will pour out of every line you disconnect and keep on coming so long as the lines are loose.

The original plastic lines don't much like being crimped closed with Vise-Grips and the like.

DELETE DELETE DELETE I hit a wrong button and it won't let me delete this.

Rupert8 said:

*If I cut the fuel lines to replace the couplings to fit a new valve, am I just going to get a tank full of fuel siphoning back at me? (If so I'll be ready. Tank is almost full....)

Click to expand...

Yes

Rupert8 said:

*Is there a common area from which these valves leak? Like the female couplings themselves? Or an o-ring on the pump?

Click to expand...

The fuel line connectors do have small o ring type seals in them. It could be the source of your leak. I've read that they are NOT fun to replace. I have no farther info on them.

Rupert8 said:

*Are there any fuel pressure - or other issues - which could cause a pump to leak? In other words, should I also be looking elsewhere?

Click to expand...

Not that I'm aware of. The FSV doesn't really see much pressure. It's suction that foes through it on the supply side and practically no pressure on the return side.

Rupert8 said:

Brass valve. Yes, thinking of that method. Not sure I want it in the cab.

Click to expand...

The brass valves themselves are underneath the cab. It's only the handle that sticks through the floor into the cab.

Rupert8 said:

If I cut the lines I'm just going to have the diesel siphoning out, correct?

Click to expand...

Again, yes.

I will add this, you can slide ordinary rubber fuel line over the cut plastic line and double-clamp it leak free for years and years.

It is easy to slide as much as a foot of the plastic inside the rubber.

There are two sizes; the Grey Return lines are ?I think? 5/16" O.D. and the Blue Draw lines are ?I think? 3/8" O.D.

Someone correct me on this if I am off on the sizes; I do know for fact that the Blue Draw is of larger diameter than the Grey Return.

MIDNIGHT RIDER said:

There are two sizes; the Grey Return lines are ?I think? 5/16" O.D. and the Blue Draw lines are ?I think? 3/8" O.D.

Someone correct me on this if I am off on the sizes; I do know for fact that the Blue Draw is of larger diameter than the Grey Return.

Click to expand...

This is correct. Supply lines are 3/8" and return lines are 5/16". I did this to cheat and bypass my FSV over 8 years ago and haven't had any issues.

Also, there is no need to go all out on some expensive name-brand valves; most all of them are made in the same Chinese factory and all have the same internals.

I have had expensive name-brand valves apart and el-cheapo Chinese ones apart and I can see no difference nor reason to spend all that extra money.

Got it. Thanks, all. Very helpful information as usual, I feel more prepared going into this now.

Think I'm going to get the Pollack valve and figure out how to connect the existing lines to it for now, wish the connections were in the same place. Will look into the brass valves at a later date, I do like the idea of keeping it simple and non-electrical.

Not looking forward to siphoning 25 gallons of diesel but here goes.....

Rupert8 said:

Not looking forward to siphoning 25 gallons of diesel but here goes.....

Click to expand...

Don't siphon......; just drill several zip-tie holes around the rim of a couple 5-gallon buckets and place them in strategic locations.

Take a line loose and have your assistant zip-tie it to the bucket top such that the fuel goes in the bucket.

Just don't get this started and then head off for several days as your buckets are going to run over.

Just as an update - and in case it helps anyone else down the line - here's what happened.....

The leaking fuel selector valve on my 1986 F250 6.9 turned out to be a Pollak, although I don't see a model number. While I'm not sure if it was the original valve, the wiring harness certainly did look like it was original to the truck. Neither the style of the valve or the harness matched what any online or in-store reference pulled up for the truck, and did not fit. So perhaps Ford changed the FSV mid-way through the 1986 year?

But if it helps anyone, I ended up buying a Dorman DOR 904-454 (the same valve I was snarky about, above....) and a Standard Ignition STD S544 wiring harness.

The valve matched right up but of course I had to connect the new harness to the old wiring. Worth noting that the new harness has six connectors whereas the valve only needs five. Just leave one disconnected - by comparing the harness to the valve you'll see the prongs on the valve aren't centered - and the female connector on the harness to ignore will be obvious. I just snipped the wire.

Not sure about wiring colors on other years or trucks but attached is a photo of my old harness. I just copied the order over to the new harness (making sure to have it facing the same direction...), leaving the single side prong in question unconnected. It is as follows, with the harness oriented as in the photo:

(Blank, on the new harness - imagine it to the left of the brown in the photo)
Brown/white
Red
Blue/yellow
Yellow/white
Yellow/green

I didn't need to drain the tanks, I just took off the rear tank quick connectors and stuck them in a bucket and let them slowly drain while I quickly moved the front tank and feed connectors across. A little messy but not too bad.

All seems well. I haven't had time to drive the truck yet but I've run it idling for a while and taken it up to 2000 rpm and no leaks, and the truck seems to run fine. The fuel gauge works as it should.

I'll add more details here if any issues pop up. Fingers very much crossed.

If this valve does go south I'm definitely leaning toward bypassing it or adding in the manual in-cab valve.

I hate all fuel line retaining clips.

Thanks for all the help along the way.