sucking air from somewhere?

[whitehorse]

Ok my truck just started this mess. The rear tank you can run until empty,but the front tank can be full plumb up to the filler neck but it cranks and idles high and skips like its got fouled spark plugs!!?....wait it don't have them,.... anyways it will clear up when I go back to the rear tank. Is this the tank switch doing this or is it something else going bad? Tim

 

[argve]

I would recommend checking the fittings and lines between the valve and the front tank. I suspect this is where your problem lies, or you have a leak at the top of the tank on the pick up tube - I don't expect this to be it but it's worth a check if all else fails...

Now it could be the valve but if you still have fuel in the rear tank and it does it then that pretty much rules it out because the pick up is covered by fuel so it could only suck fuel.

I truely suspect you problem is bad lines or fittings between the valve and tank. Probably a rub spot or something.