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Well, I finally got this tank running and smogged. Smogging it required the carb to be rebuilt, which made a HUGE difference in how it runs and smells. It passed very clean. Now I have to deal with the fuel tanks. I have searched the forums here but didn't seem to find what I am looking for. I have, of course, two tanks. I am not sure if the fuel gauge works properly or not. I put $40 in the front tank and $30 in the back tank. My selector switch is set to the front tank. I cannot be sure, but I recall the fuel gauge sitting on empty. Now it looks like it is just a hair above empty. Maybe by the width of the needle itself.
I watched videos about checking the wiring on the sender unit to check if the sender or the gauge is bad, but those videos were all single tank scenarios. Can one of you smart as hell people explain to me how the system with two tanks works please? Does it read from both tanks at once and average or what? I don't get it, nor do I get how to troubleshoot it.
Thanks,
JSM
You should have a control on your dash to switch between the two tanks. It's on the heat/air control...far right (up and down switch). Pretty sure it's not marked. there's a drawing of it in the owners manual.
My switch is on the left side of my seat on the floor. Like a large toggle switch that says Main and Aux. But that does not help me in regards to the gauge though.
JSM
Are we talking about a 78? Then it "should" have just the environmental control panel switch only, if the dual tanks are OEM. But since you have a tank selector switch on the floor, I bet you could have a dealership installed aftermarket dual tank? And the dash switch is just for the selected sending unit fuel quantity reading.
What does the dash added red flip switch do? What about the one under the steering column ?
As I understand it with an OEM set up, when you change the dash switch that changes the elec valve back by the aft tank, fwd crossmember and changes over the signal from which ever sending unit of that tank you selected.
Well shoot. All of that was darned helpful. I'll have to reread most of it tonight when I get home. As far as those two switch, I think one is for the cheapo fog lamps that are on the front bumper. The switch under the steering column, I can't say yet. It goes up under the dash and disappears up into a huge amount of other wiring. You know the drill, all of the factory stuff plus everything else anyone ever spliced in since. Sigh. But once I know, I'll report back with an update.
Thanks,
JSM
Hey Jigsaw
What I have done in the past is get a single pole double throw toggle switch.
If I remember correctly, the dash fuel gauge wire was cut and goes to the center of the switch, then run wires from the tank sending units to the switch, either the front tank goes to the top
of the switch And the rear tank goes to the bottom of the switch.is your preference.
Easy to wire up and you can check the amount of fuel in either tank any time.
If you are interested,,Do your research and look into some wiring diagrams.
Just an idea .02
Hey Jigsaw
What I have done in the past is get a single pole double throw toggle switch.
If I remember correctly, the dash fuel gauge wire was cut and goes to the center of the switch, then run wires from the tank sending units to the switch, either the front tank goes to the top
of the switch And the rear tank goes to the bottom of the switch.is your preference.
Easy to wire up and you can check the amount of fuel in either tank any time.
If you are interested,,Do your research and look into some wiring diagrams.
Just an idea .02
Better yet a double pole double throw toggle switch and wire 1 half for the gauge above.
Then pick up a fuel switch valve for a 81 F150 with a 300 six and duel tanks.
It would replace that lever valve you have next to the seat.
Power to it lets fuel flow from 1 tank and no power from the other tank.
You flip the switch and the gauge reads from the tank being pulled from, works great.
I dont know what your dash switch is now but thinking single pole double throw toggle switch?
I also dont know how it is mounted but you may want to look into the dash switch for the same 81 F150 duel tank truck as it looks to be the same.
This is the HVAC panels from said truck. The one on the right has the fuel switch on the left side of the panel.
Just my .02
Dave ----
Ok, got it worked out. My gauge selector switch is the switch on the heater/ac panel to the right. Down is the rear tank (works) up is the main tank (does not work). I think the sender unit is bad in that tank.
JSM
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