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Jeep Electrical for Dummies!

Jeep Electrical for Dummies!

jzak

Old Time Jeeper
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Location
Pittsboro, NC
Vehicle(s)
1981 CJ5/258 4.2L I6, Tremec T-176 4-speed, Dana 300, Power Steering, Howell Throttle Body Injection System, Warn Locking Hubs, Warn Rock Crawler front/rear bumper with Tire Swing Carrier, Full Roll Cage, Pro Comp ES9000 shocks
So I need somebody to walk me through this like you were talking to a 8 year old. How do you test a Fuel Gauge and Sending Unit on a CJ5 ? My fuel gauge was working fine and then it just stopped for no reason. I didn't change or add anything to my CJ. Just one day it was working, and the next morning it wasn't. I thought maybe some kids had syphoned the gas during the night, but it turned out I had a full tank.

I've spent hours online researching websites discussing this issue, and all of them assume that your day job is working as a Electrician. They start going into terms like Ohms, Resistance, Amps, and they might as well be speaking Mandarin. When I downloaded a CJ5 wiring diagram, I thought my head was going to explode. I bought a voltmeter, but I have no idea which of the 20 "Hieroglyphics" on the dial I should set it to. The farthest i've gotten is using the voltmeter to confirm that the powerwire on the fuel gauge is working, but the fuel sending wire showed no power, but again i have no idea if i set the voltmeter to the correct setting. I checked all the fuses, and they're good.

In desperation to find a quick fix, i bought a new guage. After I installed it, it didn't move, and now the gauge makes this crackling sound like there's a mouse behind the dash. I know its the fuel gauge, because the sound stops when i disconnect the power wire.

When it comes to CJ mechanical stuff i'm fine, but with the exception of switching out a light bulb or hooking up a car stereo, I am completely lost with the Jeep electrical system. So if someone could give me a layman's step-by-step explanation on what I need to do to get me out of this hole, i'll mail you a case of beer, but don't tell me to get a degree in Electrical Engineering! :D
 
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Good luck. Are you sure that you installed the new gauge properly? The crackling sounds make me think you may not have. That will fry your gauge. And it won't be worth anything and won't help you diagnose.

I am by now way an engineer. I have just learned through trial and error and the web. Youtube can be your friend here. You will want to use the ohms setting on the multimeter/voltmeter. It is the upside down U with feet. ;)

Full the reading should be low. Empty it will read a higher number. Sorry, I cannot recall the values, but if it reads anything at all then it is probably the gauge. If no readings I would think it is the sending unit. Use Youtube to find what posts on the gauge to use for testing the readings.

I have had to replace 2 gauges and now I am needing to replace the sending unit. It sucks. Also make sure your grounds are good. I have had lots of grounding issues.

I hope that I dumbed it down enough. That is the level I know it at.
 
UPDATE: Christmas Miracles do happen ladies and gents. So I took out the speedo again, and this time I thoroughly tightened the nuts going into the fuel gauge. Last time i just used a pair pliers to tighten them down. Turned the ignition and the fuel gauge started working again. Good Times! :chug:

Thanks for the help guys!
 
UPDATE: Christmas Miracles do happen ladies and gents. So I took out the speedo again, and this time I thoroughly tightened the nuts going into the fuel gauge. Last time i just used a pair pliers to tighten them down. Turned the ignition and the fuel gauge started working again. Good Times! :chug:



Thanks for the help guys!


Glad to hear it. Maybe it was the jumper between the temp gauge and the fuel. Hope you don't run into any other issues.
 
Glad to hear it. Maybe it was the jumper between the temp gauge and the fuel. Hope you don't run into any other issues.

Thanks! I'm also guessing it was the ground jumper between the two gauges. The arm wasn't laying flat on the ground bolt, so there wasn't a good contact.
 
I hate when things fix themselves. it makes me look bad.:D
 
I hate when things fix themselves. it makes me look bad.:D

No Worries! Knowing my CJ, i'm sure some new electrical gremlins with popping up eventually. :D
 
I strongly urge you to run a dedicated ground wire from the dash's panel directly to the battery's ground. 12-14 gauge stranded wire will work fine.

LG
 
I strongly urge you to run a dedicated ground wire from the dash's panel directly to the battery's ground. 12-14 gauge stranded wire will work fine.

LG

Alternatively, mount a common bus bar with 1/4" terminals on the interior, ground the bus bar with 8 ga stranded wire to the battery ground and ground everything on the interior to it.

That solved all my "maybe it's poorly grounded" issues.

-Jon
 

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