Dual Tank Switching
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Junior User
Joined: Jan 2004
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From: Sacramento
Dual Tank Switching
Hi all, I have a 1976 F150 4x4, shortbed. It has dual tanks, one behind the seat and underneath the bed, filler neck behind rear wheels. The factory tank swith by the climate controls does not work, and the previous owner had a green KC light rocker switch installed for this purpose, however flipping the switch seems to have no effect on the truck, as I have burned enough fuel through it to see that it only draws from the tank behind the seat. I would like to have both tanks, as my 390 gets quite thirsty. In either position, the fuel gauge does not work. I have checked all the fuses and they are fine, so I cannot determine why the gauge is not working for either tank, nor do I know how to figure out what is not allowing me to draw from the AUX tank. Thank-you all in advance for your help.
Posting Legend
Joined: Sep 2001
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Get a schematic for the tank selector system and find out how much or what has been modified, -then repair.
Good luck, the tank selector system is a pain. It was set up so that the fuel gage indication only switches if the fuel selector valve actually moves.
Good luck, the tank selector system is a pain. It was set up so that the fuel gage indication only switches if the fuel selector valve actually moves.
New User
Joined: Jan 2008
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Sero, I assume there isn't a valve down on the floor behind the driver to turn as well ?
As Eric stated, you need to crawl under and see what you have installed on the truck for valving.
The Factory switch was also wired in for the gauge reading per tank.
See what you have under the truck and report back.Meanwhile I'll see if I can find an illustration for the dual tank fuel system.
As Eric stated, you need to crawl under and see what you have installed on the truck for valving.
The Factory switch was also wired in for the gauge reading per tank.
See what you have under the truck and report back.Meanwhile I'll see if I can find an illustration for the dual tank fuel system.
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Junior User
Joined: Jan 2004
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From: Sacramento
Mil1ion- you are correct I do not have the switch on the floor; its old hole was covered with the nice 70's **** house carpet that now covers the floor of the cab. I was told that the aforementioned green rocker switch worked well at one time. Thank-you for searching for the schematic, I imagine that switch has to be connected to the valving setup in some way if it did work correctly at one time. I will be pressure washing the truck off today for inspection, as I couldnt resist a little mudding when I got her home. Truck is in the gallery, Spirit of 76. Pics are outdated, and I should be taking additional pictures today. Thanks
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Joined: Jan 2008
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Unfortunately none of my books shows the fuel delivery system in detailed illustration.
Look for a fuel selector valve in front of the rear tank... along cross member or frame
I have an illustration of the 80's but that is much different.
Look for a fuel selector valve in front of the rear tank... along cross member or frame
I have an illustration of the 80's but that is much different.
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Junior User
Joined: Jan 2004
Posts: 65
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From: Sacramento
Thanks anyway Mil1ion. I was under the dash yesterday and I noticed that there was a four wire plug (very similar to the plug for the voltage regulator) that was unplugged and dangling. On the driverside wall under the dash was the receiving end for said plug and upon plugging it and replacing the battery, I had my gas gauge back. One small victory for me. I also laid underneath the truck and discovered that the selector and the switching valve are in there stock location, however the switch itself has been removed and a wire runs under the carpet toward the steering column. I have yet to trace the wire to its other end. When I do I should be able to determine whether or not I need a new valve. Are they relatively cheap/easy to find? thanks for your help all.
