Gauges.....

[rhelomass]

I know many of you have seen this problem all over the place, but mine is kind of stupid, and im tired of dealing with it and want it fixed ASAP.

So my fuel and temp gauges dont work. I dont know what it is, i have checked ohm readings, wiring, grounding, have new gauges and sending units. I have tried everything suggested i can find.

Threads i have looked at and tried:
http://www.jeep-cj.com/forums/f7/fuel-gage-14487/index2.html
Fuel and Temperature Gauges Troubleshooting 1972-1986 Jeep CJ's

and many others that i cant remember.

I have looked at a wiring diagram of what it should be and it fits perfectly. The wire going from the temp gauge to the fuse box is fine and connected correctly. The one going from the fuse box, through the firewall, out of the other side of the fuse box, and then to the temp sending unit is fine. The metal tab going from the temp to fuel gauge works great. the pink wire to the sender is fine as well, the red one is also great. I cannot find the problem anywhere.

The other day, the temp gauge was showing MAX hot, but it was just some contact that I fixed. The fuel gauge has not worked at all.

I replaced all the gauges, temp, fuel, electrical, and oil, but not the speedometer, which is only a little off and doesn't absolutely need to be replaced.

The only things i can think of is maybe the fuse box is shorting out somehow only just the temp sending wire, or maybe i need a new cluster. Other than that im clueless and REALLY need help.

 

[IOPort51]

OK so this will totaly off the wall but try switching the wires to the two gauges, I seem to remember seeing it backward on the diagram, the color code is wrong. and it may well just be something the voices told me.

 

[Lumpy Grits]

Sounds like your CVS(constant voltage sensor)is act'n up.
Jeep CJ Gauge & Sender Diagnostics

LG

 

[TeamRush]

The fuel gauge has a ELECTRICAL CURRENT REGULATOR built into it.

This is NOT a 'Voltage' regulator,
It is NOT an 'Amperage' regulator.

It's a CURRENT regulator, and it cycles 'On/Off' fairly steadily.

Where I would start is making SURE I had that gauge supply wire 'Hot',
The. I would check current on the 'Strap' between gauges, see if the current regulator was cycling or not (flashing light on test light),
Then I would check the wire to my sensor to make sure the power was making it to the sensor (flashing light),
Then I would check the sensor for 'Ground', if the sensor or engine block/manifold isn't getting a good 'Ground' the sensor isn't going to work.

If you have power to the sensor, and the sensor/sending unit has 'Ground' you can, for a very short period of time 'Ground' out the sensor wire to see if the gauge is working,

If the gauge is working, then there is an issue with the sensor(s).

 

[rhelomas]

(i had to make another profile as my other one (rhelomass) wouldnt work for some reason)

I looked at my wires, and in the link given (Jeep CJ Gauge & Sender Diagnostics) , it shows, from left to right, pink, connecting tab, red, connecting tab, and then purrple. I had mine set up with the wires, from left to right, red, tab, pink, tab, purple. so I switched those to match what was stated. It didn't seem to work.

As for the sensors, would i have to open up the fuel gauge to find it/them?

As for the ground, I'm pretty sure i have good ground, or else the speedometer wouldn't work right? since the temp and fuel gets ground through the cluster, shouldn't that mean that if the cluster has ground, then the gauges have ground? I may be mistaken on the speedometer needing ground, but thats what i got from the diagrams i've looked at.

Anyways, thank you all for the amazing help you've give, and hopefully will give more. I'm going to take one last look at all my grounds and make sure that those are all good.

 

[Lumpy Grits]

OEM speedo is mechanically driven.
Listen to TR-He knows of what he sez!
I strongly urge you to get a copy of the REAL Service Manual(MR-252). Chilton/Haynes is all but worthless.
LG

 

[TeamRush]

If you don't test the current regulator for function, you are wasting time.
If you don't test the voltage supply to the current regulator, you are wasting time.

The 'Ground' for the gauges comes from the sensors/sending units.
Hooking to power and testing for solid 'Ground' at the sending units will tell you if its a sensor or not in most cases.

If you have power on the sensor wire, and you have 'Ground' at the sensor, its usually the sensor.

Two things come to mind right away,
If you over work the current regulator, you can blow the gauges fuse and you can burn up the current regulator.

Test for power to the current regulator, see if the fuse is working,
Test output of the current regulator to see if the regulator is working,
Then see if the wires to the sensors have power to see if you have a broken wire somewhere.

Then hook to power and test for 'Ground' at your sensors.
If the sensor has power reaching it, and it has 'Ground' then the sensors have failed or the gauges are cooked.

Momentarily ground the sensor wire terminals and see if the gauges move.
DO NOT keep the gauge sensor wires grounded any longer than to see if the gauge needles move!

Now, you have tested the power supply, the current regulator, the gauges, sensor wires, 'Grounds' and the only thing left is the sensors...