Cleaning the insides of old fuel tanks

[Keith Webb]

Just been working on one of the fuel tanks for the gun tractor and having managed to remove the fuel guage sender I can see the bottom of the tank is covered with a sludgy tar which seems to be very difficult to remove.
When I took the tank off there were several gallons of water in it. It appears to be sound though. Interestingly the brass float on the sender has been corroded. What sort of chemical compound would do this?



Can anyone suggest a solvent which might dissolve this tar?

For the time being I'm trying soaking it in fresh fuel overnight to see whether this will soften it.

Here's a comparison with a standard tank.