Hi all . . . since my gas gauge is not working, I am thinking of replacing the sending unit on my front tank on my 1973 F-250 V8. Is it necessary to drop the tank to do this? Is there a schematic I can see that shows where things are so I can replace it? Is the access under the seat?

Also, the back tank got some water in it and now if I switch tanks, it messes with the fuel line and filter and will not run. Do I need to drop the tank and clean it out somehow? Also, how do you clean the fuel lines once the tank is cleaned so that any residue will be cleaned out?

Thanks.

 

I'll try to be as much help as I can. I had to replace all fuel components on my truck, however I only have a fear tank. In mine, it was absolutely necessary to drop the tank to replace the sending unit. However if I were you, I'd try other tests to make sure it really is the sending unit at fault. I had this same question and this is an answer I got on my post:

"Disconnect the wire that goes to the fuel sending unit at the tank. Ground that wire to the frame, making sure the frame is clean. Turn the ignition to the "run" position and watch the fuel gauge. If the gauge swings all the way to full, either the sending unit itself is bad or it has a bad ground.If the gauge stays on empty then either the gauge is bad or there is a wiring problem.

To pop the plug off for the test, you can barely get up in there with your head and see the plug. While looking at it, VERY CAREFULLY use a screwdriver to pry it off. AND I MEAN VERY CAREFULLY. It is only pushed on like a 1/8". This is only if you can’t get it with your hands."

This answer was from the user 77&79f250. Give him the credit.

What do you mean if you switch tanks it messes with it? If I were you, I'd drain the tank, and put fresh gas in, then go up to the engine bay, and disconnect the fuel line right in front of the filter, then fire it up, and it will spew gas out of the fuel line, but since it's disconnected it won't go into your engine. You'll have enough gas left in the bowl to let it run for a little bit. You only need it to run long enough to flush the fuel lines with fresh gas. I'm not sure if this is the "correct" thing to do, but it's what I'd do.

Hope I helped, good luck.