Fuel spill

[Jon Simmons]

I have a 4300 international box truck and fuel is leaving the driver side tank going into the passenger side and coming out of key hole of fuel cap and it also has pressure built up on and need some help on how to fix it

 

[The patriot]

Sounds like your crossover line is clogged.

 

[Hoefler]

Sounds like your crossover line is clogged.

Or the cross over line valve has been closed.

 

[The patriot]

Yea, well you SHOULD turn off the valve before opening the AN fitting.
I've had them stuck in the opened position on me before.

 

[Mikey-KE7LBB]

Another thing to check is the tank vents...

It is mud season here in WY and there are plenty of times when a truck will run out of fuel while the other tank is full! The tank that is full is usually the one that has the clogged vent and draws a slight vacuum and all of the fuel from the return goes into that particular tank while allowing the other one to run dry. The opposite will apply when a non-vented tank allows the air to escape from a tank with a vented fuel cap which will allow all (or most) of the return fuel to go to that tank.

There are two types of fuel tank combos and you need to figure out which one you have. One is a tank that has a non-vented fuel cap and a one-way vent that only allows air in as fuel is used. The other is a sealed tank with a vented cap. Easy and cheap fix to knock the crud out of a vent hose or replace a bad fuel cap! Also, check the crossover line for a closed valve or clogging as others have pointed out.