86 F350 6.9
My tanks read empty at the gauge halfway through each tank (I have to put about 9 gallons in either when it hits E). I've owned the truck for about half this year, so still working some bugs out.

The front tank's sender had stopped working a while ago. I dropped the tank, pulled the sender and cleaned it up, and it read within resistance specs that I found on here. Put it back in and worked again (but hitting E halfway through the tank). I'm trying to avoid the $80 price tag per sender, and trying to figure out why they're both reading off at about the same rate.

Moving from CA to ID in a few weeks, so trying to get this resolved before I'm driving through Northern Nevada with all my stuff in the bed, and my T-Bird being towed behind...

 

First guess, the sending unit arm needs adjusted because someone bent it.

Second guess, the insturment cluster voltage regulator is going bad sending the wrong voltage to the gauge, making it read wrong.

 

I originally thought it would be something with the sending units, but the fact that both are reading E at half a tank tells me it's something else. I just filled the front tank, so I can't drop it to mess with the unit and see when exactly it tells the gauge E, but I'll check after I empty it enough.

If the issue is in the instrument cluster, what can I do to test for it? I'm working in Los Angeles for a couple of weeks, so my DMM is a few hundred miles North of me at the moment...

 

Anybody know the pn# & price of the "instrument cluster voltage regulator"??? Where can it be purchased?

 

Ouch, they're about $46.99 through all the chain stores...

Once again, any way to test things to see if this is the issue or not? I forgot I do have my AC/DC clamp meter/DMM with me down here, so I can test whatever I need to.

 

Maybe the float bowl has corroted a small hole, and has filled abit with fuel, causing it to sink in the fuel tank?

 

Already checked that, the one I dropped is solid. It's definitely an electrical issue...

 

Right now I can't for the life of me remember what the insturment cluster voltage is susposed to be.

Working to many hours I guess, brain dead.

 

It took me a lot of reading to find it on here initially, not about to start looking for it right now. I feel you on the too many hours and not enough working braincells by evening.

I mentioned my prob to Franklin2 in the electrical forum, and he has a theory about some resistance in the ground throwing off the reading, so I'm going to try to check into this tomorrow, if I have the energy after work...

 

iv been driving 1989 7.3 IDI and since the first year the fuel gauges have been bad. Been replaced already by Ford and they went bad again. Iv just calculated my mpg and know how many gallons in the tanks.

 

Mine is a 1989 as well. Regardless of which tank the selector switch is on the needle in the gauge will move from empty to well above the full mark. If I start with a completely full tank, after driving for about 130 miles, the needle moves just a little yet remains above full. The closer I get to empty, the more erratic the needle moves. For example when going around a sharp turn the gauge might go from completely empty to beyond completely full when the actual level is below a half tank. This happens with both tanks and its been that way as long as I've owned it, never got better or worse. I'm planning a two tank replacement in the near future (already bought two 19 gal PVC tanks and a Holley Red pump) and thought I'd research the guage problem before starting. I'd love to correct the problem however I'm not throwing good money at a bad design!

 

thats the exact same thing that happens to mine. just something ill live with.

 

I'd go off of the mileage if I had the correct speedo gear. Mine was already removed when I bought the truck, put in a random one from the junkyard, and learned why the last one was pulled. The speedo needle would just spin around and make tons of noise. Replaced that, but still haven't crawled under the truck to count the drive gear to see what driven gear I need...

And still haven't crawled under the truck to check the resistance of the sender ground either. Spend all day doing flooring, back is KILLING, and I have some cold brews to self medicate. I'll try to get to it soon...

 

Stacked up 240 retaining wall blocks this afternoon.

115 to 120 pounds each.

Wanna change jobs, I like Idaho.

 

Hows your hands ...

-Enjoy
fh : )_~