Black gas mystery

[Slow Poke]

I have been chasing a fuel delivery problem on my 77 fj40 with a 2f. I’ve rebuilt the carburetor a couple of times (thanks Pinhead) and recently pulled the manifolds off and had them resurfaced by a machine shop. Those two things have radically improved the performance of my engine.

However this summer I’ve been struggling with symptoms of vapor lock. On hot days it will get progressively worse the longer I drive it. I have to keep my foot on the accelerator at all times or it will die from fuel starvation.

The fuel tank was definitely sketchy when I rebuilt the truck 15 years ago. I lined it with POR 15 and hoped for the best but I’ve always been concerned that it would cause a problem some day. So I ordered a new steel tank from CCOT and put it in only to have a slow leak that I’ve been trying to fix these last 2 weeks. I’ve pulled the tank back out twice now in hopes of finding the problem but today as I was draining the last of the fuel It turned black. I’m stumped. Is this something that was in the tank? (It appeared clean and nicely made when I received it) or is it from fuel lines breaking down?

I definitely have a tank leak that needs fixing. I can pressurize it with compressed air and hopefully find the leak. Possibly send it back and put another one in but what in the world is going on with this black gasoline?

 

[Slow Poke]

Mystery solved. I used some torch down rubber roofing material strips under the gas tank. The last bit of gas wicked out sideways under the tank as it was draining and the gasoline dissolved the rubber torch down material and turned the gasoline black. It was a bone head choice of material to use in that situation. Strange though that rubber fuel hose handles gasoline without any degradation but rubber roofing material turns to mush.

The gasoline tank from CCOT has leaks in the upper corners. It came with a rubber tubing that covered the seams. Had I looked underneath when I first got it I probably have noticed the problem. Oh Well. Hopefully they’ll make it right

 

[charliemeyer007]

CCOT isn't my favorite vendor. I don't think POR gas tank liner is very good stuff. Learn to inert the tank properly then Weld/braze, silver solder the leaks. Next do an alcohol resistant liner. There are gas tank rated epoxies - might be ok at the top where the gas only sloshes on the leak spot