Dumb ?: Which tank in which? Aux / main?
 

On a 79 F150. One of the sending units does not work and I am confused with out a manual.

Thanks

looks like this



A
U
X



MAIN

Thanks. So the Aux is the front tank and Main is rear. Time to use the Sharpie.

Not so fast, the rear has always been the Aux on every one I have owned, (5) Maybe there are different ones out there. Your fuel tank selector switch should say "Rear" (up position) and "front" (down position). In 1978 models the swith is labeled "Aux"-up and "Main"-down. Anyone else??? -Dale

Time to get the lacquer thinner out....nah.

My switch says Aux on the top and Main on the bottom.

I will wait for the consensus.

up is rear down is front for me

I've got a 78, on my way home from picking it up, I ran out of gas (which was frightening cuz I just filled both tanks up) I flipped the switch, but evidentally it didn't matter. we stopped for gas and it looked like the rear was main, so I poured in my couple of gallons and couldnt start it up. we went back and this time filled the middle tank. to which it fired right up...the moral of the story is ....??? I dunno, it looks as though the rear would've been the main, but I think somebody hillbilly fixed it

I've been told that the front tank is the main and the rear is the aux. On my dash the switch in the down position is the main tank and the up is the aux.

I have a 77 shop manual. It refers to the miship tank(side mount) as the auxiliary tank.

I would suspect since all trucks have a rear tank(main) that the optional side tank should be the aux.

The rear tank should be the main tank.

On my 77, The Main was the tank behind my seat and when i turned it over to AUX the gauge started reading the Rear Tank.

my 78 f-150, main is the rear.

in my 78 aux is the rear. I wonder if the switch is upside down?

the rear tank between the rails is the main always has been always will be. the aux is the frame mounted one.

Hi I can only speak for myself,but I have 2 1978 4wd supercabs and I checked them both before writing this.On both the rear tanks are marked AUX and switch is in the up position.Hope this helps