This has been the situation since I got the truck in September. I'm refilling the tank, which I assume is 19.5 gallons, when it is between 1/4 and empty. I have between 4 and 6 gallons left at that point. After filling the tank, the gauge reads 3/4 tank.

I haven't pulled the sending unit yet, but I'm wondering if this could just be a bad adjustment on the float arm?

What's your experience with this sender? Can I correct this reading error by bending down the arm on #9275? Or would this be the indication if the float is leaking and has gas inside?

 

Sounds like you have done your own best troubleshooting. You will have to pull the sending unit to test the float to see if its gas logged and also test to see if it can physically go as high as needed to change the resistance to read full tank.

 

Joe, It aint a huge undertaking so when you have a couple hours that you can devote take it apart. Also check the ground wire for a good clean connection. You might get it all figured out in 30 minutes. The grounding can make a difference.

Personally I think it is far better to have a better idea on the empty side rather than the full but that's just me.


John

 

Thanks. I was looking here at the Advanced Search and found Bill's (ND) repeated suggestion about the leaking floats. I would never have suspected that, as it seems a gas-logged float would never rise.

Thanks John. I agree with the E side being more important, and I haven't run out of gas yet and it's also why I haven't done anything about it yet. But it's annoying to fill up and have the gauge at 3/4.

I'll check the ground too. I know on my 51, the ground was provided by the attaching screws and the wire wasn't even on the truck when I got it. But that was the least of the things wrong with that truck when I got it.

 

*1961/69 in-cab fuel tank contained 18 gallons. 1970: Ford replaced this tank with the F100/750 (1970/72) tank that contained 19.5 gallons.

This 19.5 gallon tank (D0TZ-9002-A) is repro'd by Blue Oval Truck Parts.
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The float is made of two pieces of brass soldered together. Solder breaks down, gas seeps in, float begins to settle to the bottom of the tank.

C0AZ-9202-B Float is the same: 1957/79 Passenger Cars/Trucks, 1961/79 Econolines & 1966/79 Bronco's, it's available from Ford.

The in-cab tank fuel sending unit (D7TZ-9275-G [replaced C1TZ-9275-K & D0TZ-9275-A]) is the same: 1961/77 F100/750, it's obsolete but there are 100's available NOS

 

Thanks for the reply Bill. I read your comments about the leaking float in a couple of other threads after I did an Advanced Search. And I don't doubt that's what's wrong with mine, but I don't understand how the float works at all if it's full of gas. Wouldn't it not float at all? Or if it is leaking, wouldn't the indication change over time? Mine has been at 3/4 full on the gauge after fill-up since I got the truck.

 

It may not be full of gas, but it could be filling with gas.

 

The float can be partially full, or enough to reach neutral buoyancy, the gauge will flop all over the place while driving. Eventually though it will fill up with enough fuel where it will just sink and the gauge will read empty or near enough.

Take the sending unit out and manually swing the sender from low to high/stop to stop and observe the gauge indication. Somebody here has discovered the gauge itself has at least some adjustment. But it's easier to adjust the sending unit I'd think?

The aftermarket sending units are adjustable for calibration anyway, via set screw on the arm where it connects, if the float arm is already at the stop bending the arm won't help. To calibrate one has to change the clock angle of the arm relative to the sender "axle". Move it about a 16th" and try again.

 

Ah, I see what you mean.

My gauge doesn't "flop all over the place", so does that mean the float is not filling with gas?

I'll be taking the sending unit out for testing.

Thanks for the replies fellas.

 

Any combination is possible, I suppose. Maybe it just needs calibration sounds like. The gauges are accurate enough when set right. My 64 takes 12 gallons when at 1/4 tank after adjustment, haven't tried running it dry to get it super accurate. The replacement tanks are supposedly 19 gallons, but recall there is always a certain amount of unusable fuel at the bottom of a tank, maybe a gallon.

 

Thanks Tedster. I'll update this thread after I've figured it out.