Wireing for Auxilury Tanks

[Jimbo]

I have a 69 F-100 Custom Cab with 3 tanks. I am not getting the fuel gage to work right on it. It looks like some one rewired it because I have a couple yards or extra wire under the dash. I would like to get them to work right. Thanks for any information that you can pass along. I have tried to look at the wire diagram for a 67 but that only showed 1 aux tank.

[68F250]

Hi Jimbo!

A couple yards of extra wire? Hey what's the price of copper nowadays?

You have a "custom" job there. We have to figure out how it was done before we can fix it. Question: How do you suppost to know what the fuel level is in each tank? Is there a switch somewhere to select what tank you're on? Is there also a separate valve that you use to switch between the tanks? Need to understand the system.

Barry

[Jimbo]

It has a switch on the side of the driver on the floor to switch tanks. There is a toggle switch on the dash next to the steering colum (right side). Two wires are blue (rewire) then I have a black and a white one.
Thank you for any information that you can pass along. Jimbo

[68F250]

OK, trying to understand it a little better. So the fuel tank switch lets you switch between three tanks?

The toggle switch has three wires going to it? That's not enough to do the job. You would need one wire from each tank sender and then another one to go to the gauge so that makes four. In fact I don't see how it can be done with a toggle switch, not enough positions. A rotary switch would do it though. The cab tank sender wire is orange, do you see it anywhere? Maybe it's been disconnected.

[Jimbo]

It has has 4 wires one black, one white, and 2 blue. The toggle switch has a place on one end to connect 1 wire in the middle a place for 1 wire and then on the other end a place for 2 wires. The 2 blue wires are connected to them, the white wire is in the middle and the black is on the other end. You can E-Mail me direct if you want my address is
whitehorsefcf@hotmail.com. I need to get a wire diagram to figure this out what wires go were and what color they are. Thanks for the info.
Jimbo

[68F250]

Hey you're welcome!

I'm gonna have to wait 'till tonight when I can look over the wiring diagram.

Still don't see how a toggle switch can switch three inputs to a single output. Does the switch have two positions like left or right, up or down? If it does then it can only switch between two inputs into one output.

[Jimbo]

It has a left - middle - and right. I will be going out to the truck in a little while and see what the switch say on the dash. I think it says something about travel tanks. Left Main Right. I tried LMC Trucks and they did not have any kind of switch. I would like to get the right for the job. Thanks again. Do you need vin to help with this? Jimbo

[68F250]

Ahh! A three position toggle switch and the center position is not an "off". That explains it enough, thanks for clarifying!

I don't think I need the VIN for this.

Let me first check out the wiring diagram tonight before we start troubleshooting, ok?

[Jimbo]

I just went under the truck and found it has an electronic fuel pump. It looks like someone did not know what they were doing. I have 1 blue wire comeing from the left tank and 1 blue wire from the right tank. They go up through the firewall to the switch. The fuel pump has 2 wires the black is a ground the red wire goes through the fivewall to something (have not check yet). There is a wire harness that is down by there that has a red wire that has been cut. This is driving me nuts. Thanks again Jimbo

[Jimbo]

I think they are stock. I have not pulled the dash to see where they go from the switch. I think the main tank is working does not look like the other 2 are. The switch is located on the dash next to steering wheel and the choke is on the right side. The tag on the dash say travel tanks Left Main Right. Thanks for the help so far.

[68F250]

Cool! So the gauge has life, that helps a lot. Let's start at the switch and see if the L and R positions work. You see where the two blue wires for the L and R tanks attach to the lugs on the back of the switch, take a jumper wire and ground out one of the lugs to the dash, it doesn't matter if the blue wire is attached or not, whatever is easier. Now turn the ignition switch to accessory and flip the switch to L. Watch and see if the fuel gauge rises to above the full mark. If nothing, flip the switch to R and see if it does now. If still nothing, flip the switch back and forth a bunch of times and see if that makes a difference.

Now assuming that one of the positions did send the fuel gauge above full, remove the jumper from that lug and go to the other lug with the blue wire and ground that one out. Flip the switch to the other position and see if the gauge goes past full again. If nothing, flip the switch back and forth again like before. If it does, then the gauge and switch are functional and we need to work back toward the L and R tank senders. Lets stop here and see if we get this far (fingers crossed).

[Jimbo]

I will give it a shot tomorrow as I have to take off soon for dinner. I do not have a garage so all my work is done outside. It has been raining here the last couple days.

[Jimbo]

I think I am going to need a wireing diagram to do this. I have a short in the system some where. When I put on my brakes the dash light comes on. When I use the right turn signal it works untill I put the head lights on. Do you know where I can get a wire diagram for a 69 F-100 Custom Cab. It has a 302 engine It is problably a late 69 or early 70. Thanks.

[68F250]

Yeah it sounded like you got a rats nest under there. A wiring diagram would be a good investment, time to go shopping:

http://www.osborn-reproduction.com/cata ... sition=PAR:

[Jimbo]

Thank you for the information. I will keep you updated on how this turns out. The main gas switch is working but not the other two. Thanks again. Jimbo