I have a 78 chevy and my dual tanks are off the truck but i have no idea how to hook them back up

SOURCE: fuel gauge not working

Unplug the transfer switch from the dash and clean the contacts. I had a similar problem. rh tank would go max full. works fine now

SOURCE: 1982 chevy truck with dual gas tanks with guage or tank problems

all you need to do is listen to hear the tank switching valve is working. It will make a soft noise under the rear cab section with the key on with the engine off. zif you do hear it sounding the switch your tank unit for that one tank you try to switch to is a fault. Sorry no illustrated diagrams are on hand, just knowledge

SOURCE: i have a 1986 chevy 1/2 ton. the fuel gauge wasn't

When you changed the sending unit, was this in the tank? or does it have a manual that bolts to the block. If it is on the block, drop the tank (or take the bed off) and replace the float.

carsandcomps,

Guru, Premium Expert @Fixya.com

SOURCE: 2007 Chev. 3500 flatbed deisel trucks w/Dual Tanks

Unless they have a seperate switches for tanks and gauges they equallize to give you a overall reading.

SOURCE: I have a 1978 Chevy

The problem is in your carburator. Was it rebuilt in a shop or by yourself or a friend?Did they know what it was going on? It could be that the float level is too low. It could be that you have the plunger rod for the power valve in the wrong hole. It could be that you just need to adjust the mixture screws on the front. I would start with the mixture screws. Turn them in until they seat but don't force them,be gentle. Turn them out 1 and 1/4 turns each and start from there. You will have to turn each one separately from here.Set your curb idle about 500 RPM and turn 1 screw out until you hear the idle start to go up and then back it off until it starts to falter or miss, them come ahead just enough to bring the engine out of that. Then do the same with the other screw. Reset your idle and rev the engine by hand, a couple of cracks and then crack the 4 barrels open and let go. If it stalls then open the idle screws about 1/8 turn and try again. When the engine will return to idle off the 4 barrels without stalling your mixture screws are set right. Make sure you keep resetting the curb idle, usually 500RPM for a standard and 750 RPM for an automatic.
If you rebuilt the carb yourself then look on the rebuild sheet that came with the kit for your engine application and make sure you have the power rod in the right hole and that you have the correct float level. Different applications have different float levels even with the same size engine. Set them for the engine you have it on, if the carb came off something else. Hope this helps.