hey all i have a 1994 f600 with the 5.9 cummins. It has dual 150 gal fuel tanks. My problem is that i fill both tanks up and it only uses fuel from passenger side tank. I have checked to make sure all the valves are open underneath. but it will not pull from the drivers side tank. I know there is a sending unit in each tank. However, is there a sending unit in the middle, is there some sort of a relay, crossover switch,one of the sending unit in the tanks gone bad, etc.... any help is apperciated it already left me stranded twice. thanks in advance.

 

Have you tried the dash mounted switch? Usually to the right on the heat/AC control panel.

 

Check the fuel caps. The driver side needs to be a vented cap in order to drizzle over to the other side.

 

ok i will check the cap. Also it does not have a switch on the inside of the cab. Is there supposed to be one? maybe someone ripped it out? or is it a self feeding process

 

There is no switch on the bigger trucks. Only the manual shut off valves underneath.

 

Funny! My 91 F700 has it right where I stated...in the heat/AC control panel, all the way on the right. Mine is a gasser though so maybe that's the factor.

 

Have you removed the lines from the both tanks to see if fuel will flow out of the lines?
It should self level if so.
And I'd think both tanks need a vent or a vented cap.

 

Yes, my correction, the diesels didnt have the switch. Ideally, you would use 2 vented caps to eliminate any possibility of transfer issue. From what I remember, OEM had just 1 on the opposite side of the suction line.

 

alright i will definatley check for blockages, and the vented fuel caps. no it was not leveling the tanks out it ran the passenger side dry then shut off. At which point i found the valve to the drivers side shut off so i turned it on

 

Well if the drivers side valve was shut off, I would say you found the problem ?

David