Fuel Selection Valve issues

[Ranchdweller]

I recently bought a 1990 F350 that had been sitting for about 2 years. It does not switch tanks. It runs normally out of the front tank. It has steady power and ground to the tank switch, and all the other wires switch on and off when tested with a test light to ground. I have been unable to find a wiring diagram to check the wiring at the FSV. I would like to know which wires go where for the fuel gauge, so i can test those as well. the gauge will fluctuate from full to 3/4, although i think the tank is full. The rear tank is full. I have the feeling the valve itself is not working (stuck and/or bad). I saw the video of the tear-down and repair of the valve, which i think mine needs, but I like to test, not guess. Can anyone assist with the system schematic? Also, are the sending units 0-60 ohm or 0-90 ohm?

 

[Cubey]

Note that the numbers are out of order for the valve on this diagram.

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Vs an actual connector (wire colors vary but always the same pinout order). #1 is on the left, #5 is on the right:

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[Cubey]

Another diagram showing the same thing, but better illustrated:

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[franklin2]

If you turn the key on without starting the engine, and then flip the switch from front to back, or back to front, you will be able to hear a definite thump in the cab as the valve switches. The red and brown/white are the power wires, it works just like a electric roll up window motor. The polarity of those wires are reverse to make the valve switch one way and then the other.

 

[Cubey]

If you turn the key on without starting the engine, and then flip the switch from front to back, or back to front, you will be able to hear a definite thump in the cab as the valve switches. The red and brown/white are the power wires, it works just like a electric roll up window motor. The polarity of those wires are reverse to make the valve switch one way and then the other.

That doesn't mean that the plastic bits inside of the valve aren't broken or jammed, it just means the motor is operating when it's told.

It has to mechanically operate inside to both: change tank feed and sending unit being displayed. It's all plastic bits attached to a tiny motor so it's possible for them to get broken.

 

[NeverHave-I-Ether]

What would cause the fuse to blow if the chassis wiring harness is disconnected leaving the cab? Have a short I can't find also.

Never-Have-I-Ether

 

[Cubey]

What would cause the fuse to blow if the chassis wiring harness is disconnected leaving the cab? Have a short I can't find also.

Never-Have-I-Ether

The positive wire contacting ground/negative.

 

[franklin2]

That doesn't mean that the plastic bits inside of the valve aren't broken or jammed, it just means the motor is operating when it's told.

It has to mechanically operate inside to both: change tank feed and sending unit being displayed. It's all plastic bits attached to a tiny motor so it's possible for them to get broken.

Just an easy step 1 in the troubleshooting process.

 

[Ranchdweller]

Exactly what i was looking for! I hope to get it checked out in the next few days.

What is the overall difference in the OE valve VS the valve that is readily available at the parts store? I'm sure it operates the same, but does it perform the same? What are the drawbacks of it?

 

[Nero]

I've used both with good results on both. The most common issue I've had with both is that if you leave it on one tank for too long (parking truck for 6+ months) the valve gets stuck at whatever tank you're set at. Usually flipping the switch a few times after the truck has warmed up unsticks it.

 

[franklin2]

Exactly what i was looking for! I hope to get it checked out in the next few days.

What is the overall difference in the OE valve VS the valve that is readily available at the parts store? I'm sure it operates the same, but does it perform the same? What are the drawbacks of it?

The valve that is available at the store is the same valve made by the same company (Pollack). But the problem is Ford had their valve custom made with different fuel line fittings and a different electrical plug. So if you do not mind doing some plumbing and cutting the Ford plug off and splicing in the wiring into the new plug, it works the same. I have also heard with the different fuel line routing it's hard to mount the universal valve back in the same exact spot.

I think I heard there is a China made valve they sell on ebay and Amazon that while not exactly the same, may plug in and be easier to fit up.

 

[Old Goat]

Yes, the market is loaded with the Chicom knock off Ford valve. It is an exact copy. Uses the same electrical Ford Plug.
Plastic Fuel lines connect the exact same way.
E-bay sells them as well as Amazon and a whole slew of of Auto par sites. Price range is $50 on up.

The original Ford Valve with the Ford name has pollack on it also. Pollack makes their own version, but the electrical plug has round pins compared to what Ford used with the flat pins.

I installed one of the chicom valves, worked good at first, then would not switch tanks. Just ran it off the rear 38 gal tank for a long time, then a month back I got to fiddling with it, and the gauge showed the front tank, but would not switch back or either way.
So what ended up going on, is I was pulling fuel from the rear tank, and returning to the front tank.....and you know what eventually happens.....I now mark my territory where ever I go. It over flows.

When I originally installed the 38 gal rear tank and the new FSV, the original Ford plug had one of the clips broken off. I found one at PNP in better shape.
Cut the PNP plug with plenty of wire, and the old one, cut the wires at the plug, this way I had plenty of wire to deal with.

The 2 wires from the rear and front tank are wired to a Weather pack plug, and the 3 going for ward are in a separate weather pack plug.
I did it this way, if i ever install the pollack one with round pins, I can make another separate plug.

One thing I found out, the early FSV like on my 86 is a smaller plug, and the later trucks uses a larger 5 pin plug.
I pulled 2 FSV from PNP, one off a gasser F250 and one off a 90 or 91 F250 7.3. And took the plug along with 3ft of wire harness each way from the valve.
I took apart the chicom one along with my original 86 one, then noticed the recess the plugs live in are 2 different sizes, along with the plugs.

The picture of the white plug in post# 2, is the older style smaller plug. Use it in the later newer FSV`s and it will not fit tight.


Look at post#7 in this thread, this is what the later plug looks like.

Wire connector/plug for Fuel Switch Over valve - Ford Truck Enthusiasts Forums

Pre-Power Stroke Diesel (7.3L IDI & 6.9L) - Wire connector/plug for Fuel Switch Over valve - Note: this thread is from 10/19....added an update on post# 14 3/22 I need a new wire connector/plug for my new FSOV I installed. have new rear 38 gal Tank with new sender and new Sender for the front...

www.ford-trucks.com

Goat.

 

[Ranchdweller]

Has anyone tried taking the universal pollack valve apart to fix the OE valve? I don't know that I'd trust a CHICOM valve for this. The last thing I want is to be broken down on the side of the road. with the intent of using the OE fuel lines and new electrical connector.

 

[franklin2]

Even the Pollack valves, whether the Ford type or the universal type, have reliability problems from day one. That is why everyone is leaning toward one large tank in the rear. If you get rid of the side tank, that also opens up more options for running exhaust.

A few years ago people were also retro-fitting brass 3 port marine valves in the floorboard to manually switch the tanks. Of course you still need a regular toggle switch to switch the sending units.

And then you have the transfer tank guys, they just move the fuel from one aux tank to the main tank, whichever one that happens to be.

I can see the advantages to carrying a lot of fuel. These trucks don't seem to mind the extra weight and you can save a lot of money, especially when you have to travel north.

 

[Cubey]

The earlier FSV (uses hose clamps) that I bought from AutoZone in their branded box is a Pollack made valve. Instructions tell you to put in line filters between the tanks and valve or warranty is null and void. I did so and so far it's still working fine after a year so far. Lifetime warranty on it anyway, so it's not a big deal if it doesn't last forever.