Auxiliary fuel tank problem...
My '05 F350 has an aux 50gal tank in the bed. It is plumbed into the fuel system via a "T" in the filler neck of the factory tank.
The system is setup so that the fuel comes out of the tank, into an Advanced Fuel Concepts valve (model 161), then into an aux fuel filter (Wix 33439), then out of the filter into the "T" into the factory tank's filler neck.
We bought the truck with this setup already installed and we've never had reason to use it; but we will be going 1400 miles at the end of the month and would like to carry the extra 50 gallons on board.
Talking to the previous owner, he used the aux tank as a primary tank and NEVER filled his factory tank via the filler neck. After checking out how the valve was wired up, it looks like it is getting +12V anytime the key is on. That would make sense if you're using the aux tank full-time to keep the factory tank full.
In my case, there is an estimated 7-8 gallons in the aux tank right now. I tried to verify flow out of the aux tank by removing the filter and turning the key on (and even running) it; hoping to see fuel from the aux tank draining out on the ground. I didn't get even a drop. I checked for +12V and it is indeed getting 12V when the key is on.
I've never owned an aux tank before so I'm not sure if this is normal for the last 7-8 gallons NOT to come out of the tank (on level ground), or if maybe my AFC valve is bad.
Any ideas? Is the AFC valve a good choice or is there a better option (less $) available?