Diesel tank

A lot of times there are two valves on the cross over, one on each tank, did you miss one?

 

Look in the tank and make sure the pick up tube isn't broken or blocked.

 

Well if you have quite a lot fuel in the aux (right) tank and low fuel level in the main (left) and no closed valves then it about has to be blocked at the auxiliary tank crossover outlet or cross over line.
Normally you would have two valves or at least check valve on the main tank so in case of an accident you could stop the fuel flow from both tanks. Sorry I cant be of more help!

 

If you have regulated shop air and a helper. Take one line at a time loose from diverter valve. Use shop air to pressurize tank,put loose end of hose in a bucket. Compare flow for each return and suction line. It would be best to have tank about equal with fuel.

 

You need a regulated supply or it won't be consistent. Still not exact,but it will give you a idea. Probably start with about 30psi then bump it up if you need to,so you don't take a diesel shower.

 

Search duel draw fuel and similar items. Lots of info on this sight.

 

Check fuel return splitter valve
Should be on top of trans where return line goes from one into two
Fuel lines collapse internally too