CJ fuel guage questions

Got this from a good web site someone recommended here. Read the last two lines for testing. It says in a nut shell, if the guage does not move from empty, the guage is bad. The next line then says if it does move, the sender is bad. So if I do this test it reads damned if you do and damned if you don't. Do the test and the needle should or shouldn't move. If it does, the sender is bad. If it doens't the guage is bad. So either way this test will find something bad. I don't get it. Anyone know of a more simple test for the sender and the guage??? I'm totally confused by this one. Allen

Testing the Fuel Sender unit on a CJ

The sender should have one wire (pink) with voltage from the sensor's isolated center post. The tab style connector and wire is a ground to the frame. Make sure it has good contacts.

To be sure the problem is not the gauge, you can momentarily short the (pink) wire on the output of the sender to ground, and this should show up as FULL on your gauge. No resistance at all will peg the needle FULL (the whole 12 volts). DO NOT hold it long in this position - just touch it and release. If the gauge does not move from EMPTY either the gauge's wiring has an open circuit (no voltage, or no connection to ground) or he gauge and/or its voltage regulator is bad. If it does move, the sender unit or its wiring is bad.

Reply to
<ABanks5
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This test appears to be intended for a system where the gauge is stuck on empty, and you want to know why. In that case you already know that something is bad, right?

Earle

Reply to
Earle Horton

Reply to
L.W.(ßill)

I'd be curious if you find an answer to this. Mine is stuck also, but on 'F' rather than 'E' and I'm not sure where to begin figuring out the problem.

Reply to
Kevin Greene

Checking the resistance of the tank sender unit is a good start. I don't have the value handy but a good service manual would.

Earle

Reply to
Earle Horton

Something is broke or you wouldn't be playing around with it.

If you ground out the gauge and it moves, then the gauge is working fine.

If the gauge doesn't move, it is bad.

If the gauge is fine, then the sender has issues.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

snipped-for-privacy@columbus.rr.com wrote:

Reply to
Mike Romain

Try here:

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Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Kev>

Reply to
Mike Romain

The sending unit in the tank is just a big variable resistor. At full the gauge gets full current, as the float drops the current runs through gradually increasing resistance until it reads empty. So, that's why with the key off the gauge goes to ")"....no juice.

On the back of the gauge check to see if there's any current at the red wire to the furl gauge. If it does have current, then it's likely not getting a ground signal through the sender. Run a jumper-wire ground from the pink wire on the gauge to any good ground. If the gauge goes to full, the sender or it's wiring is faulty.

Reply to
Gerald G. McGeorge

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