the fuel crossover line:

Only if your cross over line is pluged.

 

Yes it would as long as the crossover has no air in it the fuel will syphon to the lowest tank. Gravity works everytime! We had a customer that use to complain that his truck would not start, leak fuel out, or start, and die. He would bring it over and the fuel would have the same level, it was a month later that I was neer where he parked and it was on a 30 degree angle.

 

the crossover line is basically a 3/8" line between the two tanks that has a T in the middle to send fuel to the engine. If you fill one tank, gravity of the greater amount in the one side will force the fuel thru the line into the other tank until they are even. But 3/8" will take a while!
The only thing you have to be careful of, is to make sure the crossover valve is open. Normally it is, however, sometimes someone will close it so fuel won't come from or go into one tank.
Does that answer your question?

 

technically, newer trucks do NOT have a crossover line like the older ones did, a real crossover line went from one tank to the other and that was it. Newer trucks have a line to feed the engine that come from each tank to a junction, and a return line from the engine to each tank. The proportioning valve at this junction can often be a problem if it sticks, or has junk stuck in or near it.

 

the best set up i saw is on a abf truck they have a 2in crossover line you can fill one tank on one side and both will be the same when you are done. with what you have wont level out quick enough even if you pump slow unless you want to take about 45 min to an hour to do it.

 

another reason for the big crossover line is to prevent freeze up in the winter. only drawback was if you ever do lose a cross over line , alligators, you will dump a lot off fuel before you can shut/block it off.

 

it depends on temperature and the size of the crossover line. diesel flows different at cooler temps. you wont fill both tanks by simply filling one. they will even out after a while. the gauge may read full, but when it levels off, you will be far from full.

if i only need a small amount of fuel to get home, i will put it in the drivers side tank.