Fuel tank selector switch is on the dash next next to the heater/defrost control

 

If it's located on the right side of the heater control panel, it's genuine Ford. The switch on the left side of the heater control panel is the blower switch.

If the switch is by itself on the dash, it's an aftermarket switch.

 

In-cab tank and aft axle tank. 1977/79 Stylesides have hinged fuel doors painted body color.

If the door is aluminum and is riveted to the bed side, it's an aftermarket tank. If the fuel cap is exposed, it's an aftermarket tank.

 

Thanks Bill

great info. On the 79 bed, both gas tank fill ports are hinged doors painted the same color as the truck. On the in cab (77) tank, there is a screw in cap. Took some more pics this morning.

Thanks again



Side shot of truck. Rear port attached to a tank. middle port blanked off. Cab port attached to in cab tank

Is this the fuel selector valve?

Better look below the cab tank

Tank selector switch

 

I am not up on your year trucks but that switch dose look like a factory switch as Bill said.
Then from what others say on the in cab tank is a
The bed I can see as you said it is a 79 but what they are saying even the 77 would have the 2 fuel doors on the bed side so ?
As for the picture of that valve? it still looks like the 2 fuel lines, 1 straight in and the other 90* to the side of it making only 1 inlet, has me questing how the 2 tanks work?
I take it the hose coming in at 90* is from the in truck tank and the other running down the frame is the rear tank line?

Have you run both tanks yet? If you switch between them what dose the fuel gauge do? It should move based on how much fuel is in each tank.
Any way to see if that electrical wire to what ever that thing is has power on it?
If so when does it have power, main or aux?

FYI the normal 3port, 2 inlet / 1 outlet, defaults to the rear tank with no power.
I was on my front tank and could not figure why the gauge did not move?
The wire to the valve shorted on the frame when I pulled trailer wires and blew the fuse so I was running off the rear but showing the level on the front tank.


Dave ----

 

i also found this diagram and post from 2014 - not sure how to link it

it shows this as the selector valve

 

thanks Dave

there have been a fair number of posts about this same issue over the years - I found a diagram that appears to show this as the fuel selector valve. Looks just like it. I also found pictures on line of 77 F150s with gas tank filler cap on the cab, just like mine. So... I assume my truck was manufactured early in 77 and had a bed swap at some point (found vin tag on bed different than frame and cab). Looks like the selector switch and the valve are original

I have been so engrossed in figuring out what this is I forgot the whole reason I was asking

I replaced the fuel filter just before the carb and under the cab tank and have been running the gas from the cab tank only, and already there is junk in the filter at the carb but not under the tank

this is strange because the cab tank was nearly empty when I replaced the filters and tank looked good. Looks like it was replaced fairly recently - I could see the inside of the tank from the filler tube

additionally, the new filter just below the tank is clean as a whistle. Ran it about 150 miles on fresh gas and still clean.

so, I am guessing that this rotten looking thing, which I now believe is the valve and is on the downstream side of the filter is crusty on the inside and contaminating my fuel

Based on Bill’s response, it appears I need an aftermarket valve replacement because the old ones aren’t made anymore

so - thanks for all the insight. I think I’m off to buy a new valve