My vans fuel gauge doesn't read. It has double tanks w/2 sending units & fuel pumps. I thought that even if one sending unit was defective the other should work so I replaced the fuel gauge but that wasn't the problem. There is power going to the gauge. What should I do next? Help please!

 

When you switch fuel tanks, it also switches fuels senders, maybe that switch is the problem. I would normally suggest checking ground connections, but as you stated, the problem is with both tanks and unlikely that both have a problem.

 

I just bought an 87 ford f150 with 2 tanks and when I bought it the fuel guage was flopping from empty to full, then I filled it and it said over full, then all the sudden it said empty and (guess what it was empty, had to walk home). I had gas in the back tank so I switched nothing happened. guess it didn't switch. I have seen several posts on the net about these 2 tanks and pumps and guages and switches, non of which is good, it seems you can spend the value of the truck to fix a fuel guage problem. I have decided to fill the front tank and put some gas in the rear and carry a can of gas. I will run the tank out of fuel and check mileage to determine how many miles I can go on a tankful and then try the same with the back tank. Hopefully I don't have to walk too many times, lol. Have a good one. Geo