XJ6 & XJ12 Series I, II & III 1968-1992

Gas Guage Death

 
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Old 02-04-2009, 03:34 PM
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Default Gas Guage Death

I used to have operable gasoline guage for both tanks, but now they are both dead. I am sure this has come up before, what is the fix procedure?
 
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Old 02-04-2009, 04:12 PM
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Most common fault is the sending units. They're cheap, about $54.25 each. What makes me wonder is did they both fail at once? They seems like a rather odd occurrence. If one failed, then the other, I would suspect senders. If both at once, maybe a gauge?....I don't know.
 
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Old 02-04-2009, 04:24 PM
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Crawl up under the dash to gain access to the fuel gauge. You'll see a terminal on the guage with a light green/orange wire. Clip a wire to it. Turn key "on" and touch your wire to ground. The gauge should go to full. If not, your gauge is dead or it is not getting voltage from the solid green wire. The latter is not likely....or you'd see all the guages having a problem as they are in series.

If the guage is OK I suspect a problem with the change-over switch. Try jiggling it around, and/or check the connection at the back. Does the switch feel funny? If it feels spongy, that's a clue.

Sending units often fail but it would be odd to have them both fail at exactly the same time.

Cheers
DD
 
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Old 02-05-2009, 09:04 AM
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Thanks fellas. This morning my speedometer wasnt very smooth, it jiggles as it reads the speed. It also does not kick in untill 20 mph....
 
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Old 02-05-2009, 10:57 AM
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Check the plug on the transducer.
 
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Old 02-05-2009, 11:08 AM
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Default change-over switch

"If the guage is OK I suspect a problem with the change-over switch. Try jiggling it around, and/or check the connection at the back. Does the switch feel funny? If it feels spongy, that's a clue."

Doug where is the change-over switch?
 
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Old 02-05-2009, 11:09 AM
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Ken, where is the transducer to check my speedo?
 
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Old 02-05-2009, 11:47 AM
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Originally Posted by Walter1982 View Post
"If the guage is OK I suspect a problem with the change-over switch. Try jiggling it around, and/or check the connection at the back. Does the switch feel funny? If it feels spongy, that's a clue."

Doug where is the change-over switch?


You know....above the radio, the one for changing the fuel tanks

Cheers
DD
 
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Old 02-05-2009, 11:48 AM
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Originally Posted by Walter1982 View Post
Ken, where is the transducer to check my speedo?

Right side of the trans, maybe 3/4 way back, 2 wires

Cheers
DD
 
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Old 02-05-2009, 12:20 PM
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Thank you Doug
 
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Old 02-05-2009, 01:38 PM
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My 85 XJ-6 had the same problem when I first purchased it, no reading at all. The plug behind the change over valve had come loose. Once I pluged it back in, everything worked fine. Hopefully thats all it'll take. Good luck.
 
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Old 02-05-2009, 02:06 PM
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do you just pull the switch off the panel then? I do hope that is all it is too!
 
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Old 02-05-2009, 06:44 PM
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Default change

change over Valve or changeover Switch?
 
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Old 02-06-2009, 12:06 PM
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My 85 XJ-6 had the same problem when I first purchased it, no reading at all. The plug behind the change over valve had come loose. Once I pluged it back in, everything worked fine. Hopefully thats all it'll take. Good luck.
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Drive them daily to make them last!
 
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Old 02-06-2009, 12:27 PM
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Apparently all of this discussion is over a typo, since the changeover valve in the trunk has absolutely nothing to do with the fuel tank sender reading. He meant to say that the harness connector at the back of the fuel changeover switch on the dash was not properly connected.

Damage to this connector can occur when one of the fuel return solenoids is faulty and drawing excessive amperage: there is no separate fuse for each solenoid, so the current draw can overheat the wiring connector at the changeover switch and damage the switch.

If I was working on that car, I would go to each sender individually and ground them, since that is where the faults are most likely. That also enables you to test the gauge and switch. Absent of a reading, Doug's gauge test is the next step. Still no joy and I'd pull the changeover switch and jump across the sender terminals to the gauge and bypass the switch.

You need a good wiring diagram, some time to accustomize yourself with it and learning to think like an electron, a 12v test light and a couple of jumper leads with aligator clips. There isn't anything you can't fix by yourself on a 1982 XJ6 if you are so equipped, and the need will arise more often than the appearance of accurate troubleshooting tips.
 
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Old 02-06-2009, 07:02 PM
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Default el changeoveroo switcharoo

Originally Posted by Walter1982 View Post
do you just pull the switch off the panel then? I do hope that is all it is too!
you can reach the changeover switch plug by pulling the trip computer. how do you pull the trip computer without damaging the lacquer finish?

you can use Flossing String, nobody uses it anyway. double it and slide it behind each edge of the trip computer, pulling a little at a time. The trip computer is designed to be removed that way, it has a spring bracket on each side. If it refuses to come out, someone opened the brackets, so you will then have to remove the entire panel to get to the changeover switch.

The Floss string also works to remove the grille under the wipers. Same way.

Jose
 
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Old 02-06-2009, 07:06 PM
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Uh, dude, it's an '82. He doesn't have a trip computer, and doesn't need dental floss.
 
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Old 02-07-2009, 05:40 AM
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if the '82 has a Clock instead, it comes out the same way as the trip computer.
 
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Old 02-11-2009, 04:11 PM
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Yep I have a clock. It does not work, I have always wanted to toss the junky plastic factory one and find a classy working one instead. Ill try the floss idea. I do need to buy a test light also. Thanks so much.
 
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Old 02-14-2009, 10:12 AM
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Talking

Kieth, I had a loose connection behind the switch on the dash also. After I pried off the aluminum plate that held the fuel tank switch (and the other switch), I noticed that the wires werent pluged in completely to the switch. I plugged it all back together, put a little black electric tape on it to hold them together, and now my guages are fully functional! Thanks again everyone for saving me time and money and keeping another happy Jag owner on the road with my series 3!
 

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