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karldavidson's avatar
karldavidson
Explorer
Aug 05, 2018

Diesel pouring out of filler tube when cap removed...

Over 2 months ago, I installed a 40 gallon auxiliary diesel tank in my Ford F250. Yesterday, I noticed diesel was leaking out under my truck. I checked all connections and none of them were leaking. I remove the cap from the filler tube and Diesel started pouring out.

The original tank is 2/3 full and the auxiliary tank is full. I have taken several trips with no problem.

The ambient temperature is averaging 95 degrees. I have no idea if this could contribute to the problem.

I took the filler cap off the auxiliary tank to see if it had built up pressure. But, it did no good. When I opened the filler tube cap, diesel continued to poor out.... In fact I would say it was gushing out.

Has anyone else experienced this problem? And if so, how did you solve it? Thanks, Karl Davidson

17 Replies

  • What kind of aux tank? Have not had this happen before on my RDS gravity feed tank. If the factory tank is truly 2/3 full, not sure why it would flow out the filler neck and not down to the tank.
  • Fluid seeks it's own level. If shut off is elec. Not working right. If manual, left open or not all the way shut. Be may guess.
  • How do you have the auxiliary tank plumbed into the main tank?

    If I've read this correctly diesel is coming out of the auxiliary tank when you take off the filler cap. If that's true then you've simply overfilled the tank and the increased ambient air temperature has caused the fuel to expand and the only place for it to go is out the fill cap.
  • If it is a gravity feed tank there is supposed to be an automatic fuel shutoff installed where the fuel line enters the main tank fill hose. If that isn't done correctly, fuel will continue to fill up the truck's main tank fill hose and drain out as stated.
  • You'll probably have better luck getting an answer in the Tow Vehicle section. I'd ask the moderator to move it there.