1997 7.3 Fuel Gauge Problem With Rear Tank

clayholz

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Hello all, new member to this forum and first time poster. Recently purchased a 1997 obs 7.3 and it has become my new daily driver, and so far i'm loving it! However I'm having an issue with my fuel gauge fluctuating or going past the full mark when i'm switched to the rear tank. The front tank reads normally on the fuel gauge on the dash with no problems, it's only the rear tank. Usually when the tank is full, it'll read well over the full mark, but as i drive around it will fall back below full but the needle will jump around to full or half full or 3/4 full, and sometimes it seems to act "normal" but i'm weary to trust whatever reading it gives me. I've read a bit about different problems with the sending unit, or the fuel float, or wiring, but haven't been able to locate someone having this same problem. What do y'all think? Any help is greatly appreciated!
 

jschildm

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Sounds similar to a problem I had on mine, except mine wouldn't "jump" it was a slow process of basically going wherever it pleased. It did seem to act a little differently if the tank was full vs somewhere else. It was also on the front take. Mine ended up being a fuel float with a hole in it.

I am not sure which wire is which, someone will likely be able to chime in and help, but you should be able to ground the gage wire and make the gage go to full, and open circuit should make it go to empty. Thats how I'd test the wiring portion.
 

jschildm

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I did find this information for testing the fuel sending unit:

Fuel Tank Sending Unit

With the sending unit float arm in the empty stop position, resistance should be 15 ohms (below E). With the sending unit float arm in the full stop position, resistance should be 160 ohms (above F). The fuel gauge should read empty at 22.5 ohms and full at 145 ohms.
 

clayholz

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Thanks for the input, I need to get in there and pull the whole sending unit and check out what the issue is, i'm hoping its the same problem with the float as you had, but i'm sure with my luck it'll be something nice and expensive, or i'll be messing with wires. Not looking forward to dropping the tank or removing the bed to get to it, haven't decided which method i'm going to use yet.
 

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