i just bought it, only put 15 dollars in each tank, but im unsure if the switch even works, is there a way to test it without putting billions of dollars of gas in the van and playing with it? i bought it for work and very tight for money atm, but i have access to a car garage and all their tools.

it runs fine whether i have front of rear tank selected, though theres no way for me to tell if it even switches at all. and i was almost sure the rear tank was empty when i bought it, but it runs when its selected.

 

Try running one tank outta' gas and flick the switch. Then tap on the tanks - you should hear one that's pretty much empty. (P.S. don't try this in traffic for god's sake).