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Unread 09-13-2009, 07:08 PM   #1
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2005 WK 
Join Date: Jul 2009
Location: Birmingham
Posts: 17
Fuel gauge reading?

I have a 79 cj7, with 258. My fuel guage reads 1/2 tank but it will not let me put any more fuel in the tank. It acts like it is full. I have been to scared to test it and keep going when the guage reads E. Have any of you had this happen? Any suggestions?


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Unread 09-13-2009, 07:55 PM   #2
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1978 CJ7 
Join Date: Oct 2008
Location: Cottonflat, TX
Posts: 677
I have the reverse problem. My gauge reads full and stays on full until i reach half tank and when it starts to indicate less than full, i know i have reached half tank., at indicted half, i hve a quarter tank and so on. My problem started when i changed to a larger tank (with the correct fuel indicator float)

To know for sure, drain 5 gallons of fuel from your tank. note how much is indicated, then drain 5 more. and so on. then you will get the idea of how much fuel you have. kinda primitive, but then i have never seen a gas gauge that was very accurate. for sure you will be the only one who knows how much fuel you have.

If you want change it so that it is more accurate do a web search for one of the fuel tank sites and give them a call, I did that, and got a reference to the ohms. Played with my gas gauge but never got any of the same numbers and finely sad WTH, and do what is noted above.
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Unread 09-13-2009, 08:21 PM   #3
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2005 WK 
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Posts: 17
Thanks for the help. I will try that.
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Unread 09-13-2009, 08:31 PM   #4
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1976 CJ7 
Join Date: Apr 2007
Location: Naples, FL
Posts: 1,417
Search on some of the information John strenk has posted regarding testing the gauge cluster and fuel sending unit, he also has some links to pages with tons of info on repairing your fuel and other CJ gauges. In addition here is another link that will help you test your fuel gauge/sending unit out.

Jeep CJ Gauge & Sender Diagnostics

Maybe John will pop up and post his links and info for us.

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Unread 09-13-2009, 08:49 PM   #5
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1985 CJ7 
Join Date: Jun 2007
Location: Daytona Beach
Posts: 10
CJ7JEEP mine does the same thing. I hope someone knows how to fix this.
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Unread 09-13-2009, 09:25 PM   #6
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1983 CJ7 
Join Date: May 2009
Posts: 396
Well my gauge doesnt work at all so to double check that I have gas I put my ear to the opening and shake it. Also if there is a lot of suction when taking off the cap, it means its just about out
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Unread 09-13-2009, 09:42 PM   #7
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It happened to me for a while and then one day it stopped working.
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Unread 09-14-2009, 02:01 PM   #8
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1978 CJ5 
Join Date: Dec 2008
Location: Palmetto, Florida
Posts: 418
my 78 guage never worked, found out that the PO had disconnected the wires. after i hooked them back up, it still didn't work and i checked with an ohm meter and a test light and eliminated that it was not getting any current. i had to drop my tank because the jeep would die when you put it in gear and under a load (it would run forever at any idle sitting there in neutral), and cleaned it and sealed it with POR to eliminate the problem the gas tank was full of crud (mud and rust), i replaced the float (it was half full of gas) and the pick up filter. while i had the sending unit out, i took it apart (probably not reccommended) and put it back together, and rigged it over a five gallon bucket, using the fuel guage and a test light and finally got it to working by using rust remover and a knife and cleaned it up. i was able to move the gauge to full if i clipped directly to the backside of the unit and bypassed the needle that moves along the winding when the float moved, but could not get the gauge to budge when it was wired up correctly until i cleaned off the back part of the unit where the needle made contact. if you look at the john strenk pages and pictures you can see what i am talking about. everything was rusted and corroded before i cleaned it up. once i did that, i made sure the guage worked with the unit in the bucket and then put it all back toether. it has worked fine since. your problem sounds similar. during the cleaning process, i did not have that plate completely cleaned, and on several attempts, the gauge would only go to half full, even though i would physically move the float, of course when you take the float all the way up and the lever arm touches the unit frame, it would jump to full. i started messing around with mine because i;m a cheakskate and also figured that something with so few moving parts, sitting in a tank of gasoline, shouldn't go bad. i just hadn't counted on the rust. getting the tank out was a pain in the ***, but easy. dirty, but easy. probably worth a look. of course, once you have it out, you could go to a parts store and replace the unit. as long as you have it out, if you have it out, i'd replace the filter as well.
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