Bad fuel and temp guage

1crazy-jeeper

What's a scrambler?
#1
I've read a few posts in here and you guys all say that the fuel guage and the temp guage work together and if 1 goes out the other usually does too. Why is that and what do I need to do to fix it?:confused:
 

VinnyM

Rolling work in progress
City
Martinsville
State
NJ
#2
If i rember correct the fuel and temp gague us a non standard voltage...meaning not 12 volts. I would have to look it up for sure. As for fixing them.....How do you fee about the "rosery"...and maybe a few other choice prayers.

.....lol......

if you are sure...try new gagues.

Vinny
 

1crazy-jeeper

What's a scrambler?
#3
Domonis Omis;)

The guages didn't work when I bought the jeep. There is already another temp guage installed. I sure would like to get the fuel guage to work and wanted to see what could be done before I faught the rats under the dash.
 

RJCJ-8

SOA Member
LIFETIME
CJ-8.com Member
City
Rome
State
GA
#4
the fuel gauge uses 12 volts the temp uses 5.
there is a bridge from the fuel to the temp and the fule gauge controls the votage to the temp gauge.
here is a very good writeup on
gauge diagnostics
 

1crazy-jeeper

What's a scrambler?
#5
:cool: Man you're cool. I needed an oppertunity to buy more tools. Voltage testers and Ohm meters here I come. I'll probably take it apart this week end and see what is the problem.

Thanks for the advice.
 

SurfnCJ8

Legacy Registered User
SOA Member
City
Wilmington
State
NC
#6
me too

I have gauge problems too, but my temp seems to work fine and the fuel gauge hangs up. Used to only work from about 1/2 tank to E. This week it stayed on 1/2 & never moved and I almost ran out of gas. Is there a sending unit or something that controls the fuel gause at the tank end and do you think that may be the problem?

Please post if you get yours working, I'm curious to hear what you find out.
 

RJCJ-8

SOA Member
LIFETIME
CJ-8.com Member
City
Rome
State
GA
#7
there is a sending unit in the tank that could be the problem.
on that link it gives what ohm values you should have a various fuel levels.
you can pull the wire at the gauge, it should be pink, and check the ohm value between it and a ground source. Where it goes into the tank is on the drivers side. There is a disconnect there that you can check the ohm value from the sender. and compare it to the chart. The sender also has a ground on it that has to be connected to the frame. if there is not a good ground there it will cause issues as well.

before mine died it did the half tank thing then finally stopped working. I'm not sure it was the gauge or the sender as i replaced both when i put in the new tank and gauge cluster.
 

wm69

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
God's Country
State
AR
#8
ok, here's one for you. My jeep has the 20 gal factory poly tank and when the tanks full, the guage reads full, and when the tanks 1/2 full, the guage reads empty. Any ideas on this? My temp guage works fine.........
 

RJCJ-8

SOA Member
LIFETIME
CJ-8.com Member
City
Rome
State
GA
#9
if the sender was changed out the wrong one. looking on jeepdoc.com there are 2 seperate units one for the 15 gal tank and one for the 20.
could also be a bad spot in the sender.
 

1crazy-jeeper

What's a scrambler?
#10
Results!

O.K. guys here are the preliminary results. I didn't check the sending unit because I didn't feel like dropping the tank (just yet). On the fuel guage from post I to A I got a reading of 0.02 Ohms (good) from post I to gnd I got a reading of 51.8 O (again good) However from post S to I it regestered 1 (bad) when it should have shown 19-21 O. From S to gnd I got 1 (bad) when it should have shown 68-72. So this means a bad guage.
Since I am now replacing the guage, does any one have any suggestions. My local Advancd auto parts guy couldn't even spell CJ-8 let alone look up a part. Where do I get a factory replacement fuel guage?
 

1crazy-jeeper

What's a scrambler?
#11
I forgot to mention to you guys just how difficult it was to get the guage out. I'm sure you know that only circus performers and loose women can contort their bodies in such a way as to reach the top right nut holding in the speedo. I spent half the evening in the wrong end of town looking for a girl who was good with her hands. I found a lady named Alex. She was the ugliest woman I'd ever seen with a great big adams apple. But she told me she knew the way around tight spaces and off we went. Wouldn't you know it I was stopped by Johnny Law. I tried to explain why she was flat on her back with her feet in the air, I needed her under my dash, but he wouldn't listen. He said I was going to get screwed. I told him that if I'd wanted to get screwed I'd have gone to the dealer for the repair but he wouldn't listen. So $50 to her and $75 to the man later I have my old fuel guage out. I just hope the new one goes in much easier;)
 
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