Hi,, I'm a new member here, but not new to the site. When I have an issue with one of my trucks, I can usually find the answer here. This time I'm stumped, so I need to ask.

I have a '84 F250 crew cab 4X4 with a dually conversion. It came factory with dual tanks, but when I purchased the truck, the rear tank had been removed. The fuel selector switch has always been on "front" tank. Recently the fuel selector valve on the drivers inside frame rail started leaking, so I bypassed the fuel lines around it. I had to leave it on the frame and plugged in to get the fuel gauge to work. Now the gauge has stopped working, and I suspect it is the selector valve. With only one tank in use, I would like to remove the valve.

QUESTON: How do I bypass the 5 wires on the valve to get the front tank fuel ga. to work?

 

Its a hassle I know but why not add in a new rear tank with pump, and new selector valve? Its awesome to have more fuel in these beasts...

 

The box in the middle of the above diagram with the "M" inside is the valve. The wire coming from the gauge in the dash is the yellow/white wire. The wire coming out of the valve and going to the front tank sending unit is the darkblue/yellow wire. Take these two wires and connect them together and it should give you front tank only operation without the valve in place.

 

Thanks guys,, I appreciate the help. As for adding a tank and new valve, I would love to. I haven't had any luck in locating a new valve, and the wiring to the rear tank has been cut off. I did connect the yellow/white wire and the blue wire, but the gauge goes all the way to full when the key is on, so I am assuming the sending unit is bad. Parts are getting hard to find for these old trucks, but I keep looking. With the scrap prices being high, any old truck sitting around is finding it's way to the crusher.

I'm hoping to make this old truck into a decent driver/work truck. Hope to spray it in the next month or so. The wiring is the worst part of the truck. I would like to change the complete harness, but haven't had any luck finding one with air and cruise. SEVERAL things have quit working on it. The truck is from Arizona and is rust free, and I've converted the 460/4 speed to a Cummins diesel/5 speed. Took it from 7.9 mpg to 18.2 mpg and have power to spare. Still have lots to do.........

If anyone has a source for the wiring and/or selector valve, please let me know. I appreciate all your help.

 

Go to Autozone's site and type in FSV2 in the search box. That's the valve you need, but it's aftermarket and a little bit universal, so you have to make sure the wires are hooked up correctly like this;

You can use pollak valve. It's the same as FSV2 you find in autozone. Just different package.

The stock wiring is
1-2-3-4-5-6

(1) is not used

The pollak or FSV2 wiring is
A-B-C-D-E-F

(F) is not used

so when you use the new wiring trail make sure to map as follows:
1->F
2->E (Main Tank)
3->D (Aux Tank)
4->C (aux tank sender)
5->B (fuel gauge)
6->A (main tank sender)


If you want to check the wiring and the gauge, turn the key to run but don't start the engine, and then ground the sending unit wire to ground, and then unground it. Each time you do this, the gauge will swing back and forth from empty to full.

 

THANKS,,, I will try grounding the blue wire at the tank and see what happens. As for the numbers that correspond to certain wires, I clipped the plug so I don't know the order of the wires. The plug crumbled when I unplugged it. I can probably figure it out though.

Like I said,, the wiring is really bad on the truck, so I hope to find a donor soon. I found a bunch of wires that pass through a grommet in the firewall with splice connectors on them (10 or so). Looks like they were melted at one time. The wiring back the frame is cracked from one end to the other. I had to make several splices just to get the lights working. My horn and cruise don't work. I think the same relay controls both. Probably under the dash,,, still need to look for that. The temp ga. works with the heat off, but when I turn on the heater blower, the needle climbs. Turn the heat down, and the needle falls. A/C won't come on. Volt ga. doesn't work. I think it would be easier to change the harness than make the repairs,,,, If I can find one.

Thanks again,,,,,,

 

Yellow/Blue Stripe = A
Yellow/White Stripe = B
Blue/White Stripe = C
Red = D
Black/White Stripe = E
None = F

 

Definately the sending unit. It is working, but is not reliable. Will be ordering one in the next couple days. ROCK AUTO.COM has a Dorman brand with lock ring and gasket included for $52.79 plus shipping.

thanks for the help.

 

Your truck should be a F350. All of the crew cabs were. But 85.5 and older have the same running gear as a F250, just with a higher GVW (mine is 9300lb.) So you should have a Dana 50 TTB front and Dana 60 rear, and a BW 1345 transfer case (if it's still there); that is what mine came from the factory with, and it sounds like yours started life as virtually the same truck as mine. Dana 70 came behind the diesels.
As far as the tank selector goes; one from a newer truck is plug and play BUT, the switch on the dash will work in reverse; found that one out the hard way.............I pirated mine out of the 89 that donated it's drive train to my truck.

 

Actually,, I'm not real sure what the truck is. I was told by the PO that it was a 3/4 ton single wheel originally, with a "cowboy cadillac" conversion. My GVW is 9300 as well. There are no emblems on the truck at all. It was an Arizona truck. Last year I pulled the 460 out, along with a T19 and a 1356 case. It has a TTB front, and a Dana 70 rear. My father in laws F350 has overloads, but mine doesn't. The 460 was a strong engine, but the fuel mileage made the truck almost undriveable at 7.9 MPG. I dropped in a '90 Cummins diesel and a 5 speed, and now I average 17.6 MPG. Easy swap and makes towing a breeze.

I will try to decode the VIN if I can. I appreciate any info you can give. Always anxious to learn.

thanks,,,

 

Put your VIN into here, it might be able to tell you:

VIN Number Decoder offer to you by Ford Trucks Enthusiasts | www.ford-trucks.com

or here:

https://www.fleet.ford.com/maintenan...ls/default.asp

 

That sure made it easy. F350!! Takes the "wonder" out of it all.

I've worked for years on a different make of truck (I won't say which one...lol), and pretty much know all there is to know about them. I was never a fan of the Ford trucks, but now I own 2 of them. The '84 F350 and a '92 F150. They kinda' grow on ya. This site has helped me more than you know.

 

I think the tank selector valve I am removing from my 86 will probably work on yours along with the rear harness. I am putting later wiring and converiting to EFI so even the rear harness is coming out. It has some questionable areas from the PO's trailer wiring hookup. I don't know wher Le Roy WV is, but stuff moves between here and Falling Waters very regularly.

 

How much harness are you planning on changing? Will you be changing the harness under the hood and under the dash also? Do you have cruise and A/C on your truck? I'd be interested in a complete harness if you are changing yours out.

 

I'm changing all of them, truck has AC, Cruise etc. Unfortunately from your standpoint, I did it piecemeal so I could run the truck after I started the underhood work for the EFI system, as a result I cut the front harness on both sides where it went through the firewall. I may know where a harness is, my neighbor totalled his 86 F150 several years ago and the dashboard went to a friend in Virginia Beach. If he kept it when he changed the dashboard in his 84, I'm sure it will be available.