Fuel Tanks Not Equalizing

Good idea. I would also suggest swapping the fuel caps to see if the problems follows the fuel cap.

Make sure to label the fuel caps before swapping them.
It seems the problem has to be either a plugged vent line or plugged crossfeed.

 

Thrown away? Doesn't diesel liquify when it warms up?

 

What about big tank full of fuel makes rig drain little tank first? I don't have the english to explain my position except to attempt to show that big tank many gallons dominates little tank few gallons based on weight. Truck is going to draw on little tank.

 

Unless they have a bottom tube for equalizing, they won't.

 

Have had similar problems with 2 Detroit Engines, something gets in the fuel line and it will clog up at the cross over valve, sometimes blowing air through the fuel line corrects it. Sometimes the fuel return line will put more fuel to one tank than the other,

 

Ahh, hasn't happened in quite a while. Like you said, sometimes it will equalize other times it wouldn't. One time I had a shop take the crossover lines off and blow them out. It seemed to work for a while, but a few other times it still didn't equalize? But that hasn't happened in quite a while. However, mine would quit running from lack of fuel in the passengers tank even though the Driver's side tank was full.

 

My mechanic experience was not on trucks. My vehicles had the fuel tanks vent through the fuel caps. My remaining theory is that either a vent is partially blocked and is becoming fully blocked during operation or ditto for whatever your vehicle uses as a fuel crossover tube between fuel tanks.