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I just bought a '71 F100 long bed with auxiliary gas tank. Never had a truck with two tanks before, and the PO only had it about a year, during which time he didn't drive it much. He knew nothing about them. It has this switch on the driver's side floor, near the sill plate:
I assume that this was added somewhere along the line, right? It still has the switch on the dash. Am I safe in assuming the dash switch is inop? Or does the dash switch only switch over which tank is displayed on the fuel gauge?
Also, the fuel gauge only shows a little over half full when I fill the main tank. Not sure if it's a problem with the sending unit, or if indeed it only gets half a tank on a fill, for some reason. Easiest way to find out, I guess, would be run the tank dry. But before I do that, I need to figure out the auxiliary tank switch so I don't get stranded somewhere without gas! Any help would be appreciated. Thanks!
For what its worth, I use the dash selector. I've never gotten more then 3/4-7/8 full tanks on my '70. There are lots of posts about guys putting blocks of wood under their tires to help with the air gaps when filling. Be aware that a lot of people on here, including myself, can tell you that the main tank will spill out the fill tube on a hot day on an incline with a "full" tank. Whenever I'm filling up and going to put some miles on it, I fill it and make sure I pull from the main tank first.
I just bought a '71 F100 long bed with auxiliary gas tank. Never had a truck with two tanks before, and the PO only had it about a year, during which time he didn't drive it much.
He knew nothing about them. It has the "manually operated" fuel tank selector valve on the driver's side floor, near the sill plate.
I assume that this was added somewhere along the line, right? Wrong.
It still has the switch on the dash.
Am I safe in assuming the dash switch is inop? No, because it has nothing to do with switching the tanks. Or does the dash switch only switch over which tank is displayed on the fuel gauge?
Also, the fuel gauge only shows a little over half full when I fill the main tank. Not sure if it's a problem with the sending unit, or if indeed it only gets half a tank on a fill, for some reason.
Easiest way to find out, I guess, would be run the tank dry. But before I do that, I need to figure out the auxiliary tank switch so I don't get stranded somewhere without gas!
1967/72 F100/350 w/optional 25 gallon auxiliary fuel tank: These were only available factory installed, there was no dealer installed accessory kit.
Manually operated fuel tank selector valve located on the floor adjacent to the drivers side of the seat.
The selector switch, located on the left side of the dash only changes the dash fuel gauge from one tank to the other.
Someone, when they installed the carpeting, covered up the bezel that is below the handle that tells which way to turn the valve.
So, whoever did it...used a grease pencil (probably a laundry marker) to write the instructions on the sill plate.
The fuel sending unit float (C0AZ-9202-B) is made of two pieces of brass soldered together. Solder breaks down, gas seeps in, float slowly settles towards the bottom of the tank.
The float is available from Ford and is the same for ALL 1967/79 FoMoCo vehicles.
1967/72 F100/350 w/optional 25 gallon auxiliary fuel tank: These were only available factory installed, there was no dealer installed accessory kit.
Manually operated fuel tank selector valve located on the floor adjacent to the drivers side of the seat.
The selector switch, located on the left side of the dash only changes the dash fuel gauge from one tank to the other.
Someone, when they installed the carpeting, covered up the bezel that is below the handle that tells which way to turn the valve.
So, whoever did it...used a grease pencil (probably a laundry marker) to write the instructions on the sill plate.
The fuel sending unit float (C0AZ-9202-B) is made of two pieces of brass soldered together. Solder breaks down, gas seeps in, float slowly settles towards the bottom of the tank.
The float is available from Ford and is the same for ALL 1967/79 FoMoCo vehicles.
Thanks for the info. So the switch is stock; just the hand-lettered diagram isn't, huh? Great information. Thanks!
I figured the auxiliary tank was original; I just questioned the switch and hand-lettered instructions. My (incorrect) assumption was that the dash switched was what switched from main to auxiliary, and that someone had added the lever on the floor. I learned something very valuable tonight!
The build sheet was retrieved and saved by a previous owner years ago when he apparently had the seat reupholstered (which is a topic for another thread--WAY too squishy!!!). But it's in pieces and discolored, so hard to make out anything.
I don't know if this is considered hijacking or not, but my 70 F250 only has the dash switch. While I've never waited until I was out of gas, does this mean that a PO made the dash switch select the tank AND select the tank to be displayed on the gauge?
I figured the auxiliary tank was original; I just questioned the switch and hand-lettered instructions. My (incorrect) assumption was that the dash switched was what switched from main to auxiliary, and that someone had added the lever on the floor. I learned something very valuable tonight!
1973/74's also have the manual valve, but the switch is located in the heater control panel.
1975/79's have a fuel tank selector valve and solenoid assy mounted on the cross member.
The switch located in the heater control panel changes the tanks and the dash fuel gauge from one tank to the other.
11-14-2017, 03:16 PM
