I have recently purchased a 1978 f150 4wh.dr. as a project truck, however I had to drive it home by pulling the inlet side of the fuel pump line off and sticking it into a gas can, then leaving the gas tank under the hood to drive home. It has dual tanks, and I have no understanding with the theory of how they switch from tank to tank. Ive not found a manual valve,but I did find a device which looks like a electronic valve near rear tank, which kinda believe would be switched at instrument panel. My question is can someone brief me on this,and two should I even bother trying to get both tanks operable again or just go with a single tank? Thanks in advance!

 

If its a factory set up, the tank switch is in the heat/defrost control panel.(two switches look the same, one controls fan speed, one switches front to back tank) I'd get both tanks working if it were me. Trucks are not known for high gas milage, you want to be able to pass at least one gas station!

 

You can try bypassing the valve and running to one tank to verify that it is the valve that is not working. If you need a new valve J.C. Whittney has them ALOT cheaper than ford. And it is a bolt on replacement as well. Mine was bad when I got the truck. But it would only feed on the front tank. With just on tank I think I had a range about about 150 miles or so.

Chris

79 F-150 Lariat: Long-bed, 2wd, 460 (intake, headers, cam, early heads), C-6 (shift kit)
79 Mustang: 460 swap under way, balanced rotating assembly, forged pistons, truck rods, c-8 heads ported, Lunati solid lifter cam, more stuff...
98 Chevy Silverado ext. cab 4x4 (work truck)
95 Lexus SC300 (wife's baby)

 

All,
This dual tank thing has got me confused.
1. Is there a separate fuel line from each tank to the fuel pump.
2. Are the fuel lines joined together at the switching valve.
3. Why can't the valve be removed and the two lines be unioned. If so, you would just need one tank gage to work and both tanks would feed one line. As both tanks empty the gage should read true.
School me,
Kingfisher

 

The way the lines run is like this:

From the tank to the switching valve. (2 lines in, one out)
The line going out runs to the fuel pump (electric on mine) and to the engine.

BTW - run both tanks, you really do need the fuel!

Jim

76 F250 HiBoy
360 with mild mods (stupid dealer said it was a 460, then I found this page and voila!)
C6 that will 'bout throw your head into the bed!

 

To Kingfisher,
What you are thinking of would work IF the tanks were in a gravity feed system, that is, with the fuel outlets on the bottom of the tanks. The way the fuel lines come out of the top of the tanks, if you got an air bubble in the line it would quit siphoning and draw out of the tank with the least resistance. That might not be the one with the gauge. IMHO better to run the valve.
Just my $.02
Greg

'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
huct on foniks wurkt fer me

 

Also, if one tank is in cab and the other is in the bed, then if you just connect the two together the gas in the cab tank would run down hill to the bed tank and overflow it. I don't think this was so in 78--both were in the bed IIRC.

 

 

Has anyone ever seen A 1979 f-100 FACTORY dual tank SHORT WHEEL BASE (2 fuel doors??) I haven't... But, I just bought one. In fact, come to think of it, it's a Ranger. I'm not sure I have seen a ranger after the 72's.

 

look up the VIN under the stickies section and read the first 3 or so posts at the stickies im pretty sure 77&78 F250 has info at least a diagram on the dual tanks.


The switch should be to the right of your heater switch in the center of your dash board saying "main aux" its an up or down. Start there to see if the switch has power then move to the tank selector. Chances are you have a bad ground and the hoses are crap and the selector is bad. You'll really enjoy having the range of dual tanks if they don't leak.

 

https://www.ford-trucks.com/forums/1...ing-valve.html


for older truck but its info


Technical Index - FORDification.net - The '73-'79 Ford Pickup Resource


for vin info


https://www.ford-trucks.com/forums/1...then-some.html


scroll down to post #10 and keep reading

 

Ranger: 1965/66 F100/250 2WD / 1967/81 F100/350.

Ranger XLT: 1970/81 F100/350.

New "mini" Ranger pickup introduced March 1982 as a 1983 model.

D5TZ-9189-B .. Fuel Tank Selector Valve & Solenoid Assy-Use with dual fuel tanks: 1975/79 F100/350.

D5TZ-9A050-A .. Fuel Tank Selector Switch-Use with dual fuel tanks: 1975/79 F100/350.

Located in heater control panel, switches the tanks and the dash fuel gauge from one tank to the other.