As part of getting my new '54 6400 ready to drive home last week, I had to figure out why the fuel pump couldn't pull fuel from the original tank but could from a 5 gallon can.
I went up and pulled the tank several days before the big day and brought it back to the shop to find the problem.
Here's a couple of problems, one I didn't even know I had yet (no fuel gauge reading). Original Sender
The pile of crud was a solid plug in the pickup tube a couple of inches from the bottom. Some pounding with the end of the welding rod broke it up. The brass strip is supposed to go from the terminal on the top to a terminal on the variable resistor in the middle.
The bottom and lower sides of the tank were covered with a black stuff that appeared to be gum/varnish from evaporated gas. We later found quite a bit of it in the fuel line up to the fuel pump.
I cleaned the inside of the tank with an all purpose cleaner like you would use on a garage floor, greasy parts, stove hoods...
I started with about a pint of straight cleaner on the bottom of the tank. I agitated it several times to get the cleaner up on the sides of the tank and then let it set overnight.
I got a LOT of black stuff out with just that.
I then put in a mixture of hot water and cleaner and a hand full of new 7/16 lock washers. I taped up the openings and then slowly rocked the tank back and forth over a saw-horse. I did this for 15 or 20 minutes and then dumped the water and loaded it with cleaner and water again. Another round of agitation and I started to rinse it out with straight hot water. It looked pretty clean so I finished rinsing it and then started dumping the washers out.
The last step to dry it out was to put a quart of so of denatured alcohol in and sloshed it around to pickup any remaining water drops. After dumping the alcohol, I used the exhaust hose from the shop vacuum to final dry it. Installed Tank
If you blow up the picture, you can see a white wire on the sender from one of the mounting screws and a screw in the upright body support behind the tank. The white wire is the ground from the unit to the body which I hooked up as soon as I put the camera down.
I had a rubber hose on the tank to pump fuel line at the pump end and the tank end of the steel line hanging open. I flushed an entire can of brake cleaner through the line by putting a little in, waiting a few minutes and the blowing the line out with the air compressor. Again, a LOT of the black crud came out with each flush. It was finally getting clear down at the end of the can.
Put gas in it, turned the key, hit the starter and the engine started and the fuel gauge showed just under half a tank.