Gas Gauge

Gas Gauge
J

justinkase

Jeeper
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Location
Laramie, Wy
Vehicle(s)
1985 cj7, 4.2L I6 w/.06 overbore, T-5, dana 300, amc 20, dana 30, 4.10 gears
Yesterday my gas gauge went out and I don't know how to fix that or in what places it could be broke. Could someone please give me a for dummies explanation of how to check this out. I don't have the money to just start replacing stuff. Thank you
 
more than even chance it is the sending unit, that is in the tank and will require a tank drop to replace it. to check the gauge you can disconnect the wire going to the sending unit and ground it out while some one watches to see if the gauge responds. just ground it for a second. to check the sending unit you can check the resistence with part of a tank and at fill up and see if it changes.
I recommend you find one or both of these books to help you on the road to enlightenment. right now it is likely the best investment you can make.
this will give you wiring diagrams and pictures. you can find diagrams for the wiring at Autozone.com as well and they are free.

Amazon.com: Jeep CJ/Scrambler 1971-86 (Chilton's Total Car Care…

Amazon.com: Jeep CJ 1949 thru 1986: All models (Haynes Repair Manual) (0038345004124): Larry Warren, John H. Haynes: Books
 
Old Dog said:
X2. I THINK Brrock might have a couple different ones listed in there, all by John. Very good reading in there about gauges.;)
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X3. I've used John's stuff myself. It is very good reading.:punk:
 
justinkase said:
Yesterday my gas gauge went out and I realized that I was probably the last guy on the planet with a working gas gauge in his Cj that wasnt previously repaired.
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I have yet to have a working gas gauge in any Cj I owned. :laugh:
 
I'm pretty sure that I have a grounding problem. I started it up yesterday and the gas gauge started registering again. Thank you for the book suggestions.
 
the sending unit is on top of the tank, the ground wire is from the sending unit to the frame, not too hard to get to.

justinkase said:
I'm pretty sure that I have a grounding problem. I started it up yesterday and the gas gauge started registering again. Thank you for the book suggestions.
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Petescj said:
I have yet to have a working gas gauge in any Cj I owned. :laugh:
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I had one that worked in an 86 CJ I owned once. The wiring hadn't been violated yet. Wish I hadn't sold that Jeep. :( My current CJ has a non-working gauge. I know it's the sending unit. I have another but just don't have the time to install it yet.
 
couldn't wait to see this post! i'm on my 3rd (soon to be 4th) sending unit.
the first, original(?) broke near the resistor so i replaced it with a new one
and a week later found that the gauge had failed.. turned out the float
filled with gas and wouldn't float! got a free replacement and it is now
slowly going into the failure mode.
long story short.. if you go through the pains to replace the sending unit;
try to get a unit that has a solid float not one that is soldered together.
memory is that resistor runs from 10 to 83 ohms (GMC???)
drain the tank first!! GOOD LUCK

radman
 
This is my first cj and I am learning that there is work that I have to do on it most days. Like last night I found out that it runs like :dung: if I turn the heater off under the hood
 
I've had my 1978 CJ5 V8 AMC 304 about a month. I know the fuel and temp gauges in the speedo cluster are bad, so I've unhooked the wires to them and want an aftermarket fuel gauge. How do I test the SunPro fuel gauge the PO had hooked up? How do you test the sending unit? With aftermarket fuel and oil gauges, do they still need to be linked together like the factory did in the speedo cluster?
Thanks,
Tim
 
To those who have bypassed using the gas guage (PetesCJ and Nitor) how do you know when to fill? I'm facing that problem with a few other wrinkles. I want to believe the gas tank is factory on mine for a '66 but with the buick 231 and a shorty dual exhaust I'm guessing the mpg won't be great. It must take a little getting used to until I feel out when to fill. Also smart to keep a jerry with a few gallons on the back for the first few trips :)
 
Ya my tire rack has been modified to hold two jerry cans and they always have a few gallons in them, and my gas gauge works most of the time, weather has been bad here and I don't have a grange so I have not been able to track down my ground problem. Gotta love Wyoming, it's snowing today
 
peep6543 said:
To those who have bypassed using the gas guage (PetesCJ and Nitor) how do you know when to fill? I'm facing that problem with a few other wrinkles. I want to believe the gas tank is factory on mine for a '66 but with the buick 231 and a shorty dual exhaust I'm guessing the mpg won't be great. It must take a little getting used to until I feel out when to fill. Also smart to keep a jerry with a few gallons on the back for the first few trips :)
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Peep6543 - I know that my CJ will go about 300 miles on a tank full. So I write down the milage +300 on a piece of paper and attach it to the dash with a magnet. When I start getting to that many miles, it's time to fill up.
 
tim843 said:
I've had my 1978 CJ5 V8 AMC 304 about a month. I know the fuel and temp gauges in the speedo cluster are bad, so I've unhooked the wires to them and want an aftermarket fuel gauge. How do I test the SunPro fuel gauge the PO had hooked up? How do you test the sending unit? With aftermarket fuel and oil gauges, do they still need to be linked together like the factory did in the speedo cluster?
Thanks,
Tim
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Start by reading the links for the gauges here- http://www.jeep-cj.com/forums/f49/useful-info-thought-id-share-665/ it will tell you how to test the sending unit and gauge.
To answer your other ? aftermarket gauges do not need to be linked together. At least not if they are both aftermarket.
 
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