Dose any one have a wireing diagram for the dual fuel tanks. I think I just have a broken wire some were but I dont know how all the wires are saposed to go. It dosent have any thing in my Chiltons manual, so I thought I would check here. Its a pain having a truck that a hack of a mecanic worked on before I got it.

If it aint broke, keep fixing it till it is.

This is hard to belive no one has any suggestions or ideas. Any thing would be of help. It would be great to be able to use the 2nd tank.

If it aint broke, keep fixing it till it is.

I don't have any wiring diagrams available to myself to help you there, but I'd start first at checking all your ground connections. On old rusted chevy's that's usually the problem. My 78K20 had the dual tank added by a previous owner so my wiring's custom, but it's pretty basic power and grounds. My truck had a camper on it years ago and the guy actually had phone line running thru the frame rails for who knows what application, not to mention a birds nest of wire under the tailgate. I'm sure someone here will pick this up and give you advice on the diagram you're looking for. Good luck.

I have had good luck with wiring diagrams from Mitchell's Manuals. I live near a public library that keeps the Mitchell's Manuals in the reference section. I'm even lucky enough to get up to 10 pages of any reference book photo copied for free.
dave

Which side doesn't work? The reason I ask is because from my experience and what quite a few people have told me is that when the switch (solenoid, not the switch on the dash) goes bad, it sticks on the right tank (I'm pretty sure). That's a pretty easy fix, but kinda expensive I guess. I'd check the wires out good first I guess and then go after something like the switch.

If it hurts, soak it in cider!

Sorry i didn't see the post earlier. There is a single wire going back to the solinoid, comes into fire wall under the master cylinder to the left and low facing master cylinder. Chances are this wire just came unplugged from its little plug on fire wall. You should have 12volts on single solinoid wire when switch is to left tank and key on. Or just listen with key off for a popping sound when the switch is kicked. Try that wire first then let me know. I have more tricks for that.

I think its the selinoid thats mounted down on the frame rail, because I went trought the wires and every thing seem to be in order. For the switch in the dash dose it only send power to the selinoid when the switch is full pressed in or should it be hot all the time. It is stuck on the driver side tank wich I belive is the main tank and the one on the right is the secondary.

If it aint broke, keep fixing it till it is.

Put a test light on the one wire under the cap at the solinoid then switch the switch in the cab the light should come on when the switch is on drivers side I thought. I am basing this on my 77 truck. Is the gas guage switching? This is done at the switch. Need to determine the solinoid is bad before you spend the $30 bucks. Try putting 12v on it to see if it swaps I used a remote starter. Dont for get to put the little skid plate back on when your done with solinoid. That dash switch just turns on 12v to solinoid thats all, (and switches guage senders)

Your pre fuel injection so the switch only does two things (assuming you have a mechanical fuel pump on the block, if it has an aftermarket electric pump(s), it may do more). In normal applications the switch has 12 volts going to it, a sending wire (usually pink) going to the gas gauge, a wire going to the solenoid, and two sender inputs (one from each tank). The solenoid should have one wire going to it (the one from the switch) and it's self grounded. First check the ground on the solenoid (unbolt it, clean both mating surfaces, and rebolt it). Next take a test light and put it on the wire going to the solenoid. Then put the switch in the other direction and check it again. Assuming the ground it good, there should be power (12 volts) in one direction, but not in the other. If there is no power in either direction check the power going to the switch, if there is no power going to the switch, then a fuse is blown (change fuse)or you have a break in the wire (replace with jumper). If there is power to the switch, but none coming out when the switch is in either position, you have a bad switch (replace it). If you have power in one direction but the tanks won't switch, then you have a break in the wire (replace with a jumper) or you have a bad solenoid (replace). Another thing to check (non-electrical) is for plugged lines coming from one tank. If all electrical checks out you may have a blocked line. There are a couple more things to check and ways to check the solenoid for proper function. PM me if you have more questions. Hope this helps

If you didn't built it yourself, how can you call it yours.......

There are 2 green wires coming of the switch in the dash to the selinoid. One is a dark green the other is a kind of lime green. They only have power when the switch is fully depressed. Depending on which way the switch is pressed then then that wire becomes hot then when u press the switch the other way the other wire becomes hot. There is still power down at the selinoid so the wires are still good.

If it aint broke, keep fixing it till it is.