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Discussion Starter · #1 ·
I have a '93 YJ and I modified the fuel filler vent so it now will fill to 22 gallons (used to fill to 16 gallons).

The problem is that the gauge will show 1/4 full, but is empty. Does anyone know how the sending unit works?

Any help is appreciated.

 
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you will need to drain and remove the fuel tank, be careful, don't use a droplight or electric powertools or any pilot lights in the area. too many people have been burnt when thier drop light ignited gasoline fumes! the sending unit is retained by a metal retaining ring that is removed by carefully tapping it around with a brass punch. When the sending unit is removed you will see that it is a very simple device consisting of a float arm and a rheostat. The mechanism can be tested by reconnecting the sending unit to the vehicles wiring harness and connecting a jumper wire from the sending unit to a good ground, when the float is fully extended the gauge should read empty, moving the float up and down should show a coresponding change on the gage. if everything checks out then test fit the sender in the fuel tank to check for interference, the float arm can be bent to clear obstacles or correct the reading. hope this helps, jjc

 
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I had to replace the sending unit in my CJ due to a similar condition. The rheostat in the CJ unit consists of coiled copper wire. The wire scored and eventually broke, causing a short and the gauge didn't read properly.

 

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/wwwthreads_images/icons/tongue.gif After reading through LEVE's guide, I have decreed that the problem is that the lever arm rode higher than it ever was, and something bound up which kept it "floating" and not dropping alla way down when the tank emptied. It needs to be cycled to get the thing really free./wwwthreads_images/icons/cool.gif

CJDave
 
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I did the same modification and now my Jeep is empty when the guage reads 1/4 full as well. Someone explained to me that the only fix is to get a sending unit which is made for the 20 gallon tank. The 15 gal sending unit will not work no matter what you do to it. It isn't broken. It's just fooled like the gas station fuel pumps that now think your tank is bigger. It isn't bigger, you just moved something out of the way. A new sending unit is about $225 when I checked a year ago. I figured that kind of money will be better spent on gas so I didn't get one. I just make sure to fuel up at 1/4. Also, have you noticed by making your tank hold more, the guage reads full for a lot longer?

-Dorian
www.4Low.com
 
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Sorry, just noticed we're talking about a YJ and not a CJ. Quadratec lists Fuel system parts for CJs and Wranglers (pg118) and YJ sending units are NOT on the list. My mistake - and I agree that $225 is way too much $!

 

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Trust Larry to give you good advice. Follow it.
Seems to me that if you have eliminated the part of the filler tube that extends into the tank (I suspect it was designed this way to prevent over filling and contaminating the system's charcoal canister).
The sender's wiper has only a limited amount of coils (travel) yet the float's travel on the other side of the pivot has been extended due to the increased capacity of the tank. The only way I see to make the OEM sender indicate properly would be to move the sender rod's pivot a little towards the rheostat so that it will be able to travel the new empty-to-full distance and still have the other side move within the peramiters (travel) of the rheostat.
Moving the pivot or altering the arm/s are the only way to keep one side's travel of a lever the same after extending the travel of the other side.
It's funny... after modifying the tank to hold more fuel above the limit of the arm of the sender, it still should register similar to your old levels after your fuel level is down to the old "full" level.

JAF
 

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Discussion Starter · #11 ·
Thank you all for the responses.

Just to clarify, the guauge is normally right after going through the first 5 gallons or so. It is pegged full until it gets down to the normal full level. After that it will drop to empty. I think something must be stuck (after reading the great responses) and that it won't go below 1/4 tank. So, the gauge isn't that accurate from full to about 3/4 full (the old full mark) and gets stuck at 1/4 even after the fuel drops below that level.

With the sending units being so pricey, I think I should just go for the dual jerry can tire carrier.

-ray

 
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Maybe you are right. I never thought of looking in a catalog for the sending unit. Figured that was too sophisticated a part for any person to buy. The $225 was dealer price and who knows what they tack onto that.

-Dorian
www.4Low.com
 
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