Fuel Gauge Prob

1987 Wrangler, 4.2L 5spd

Fuel tank is new, sending unit is original, and worked prior to tank replacement.

Problem is, with switch on, gauge on dash reads full until tank is almost completely empty, then gauge drops down to

1/4 mark.

I'm scratching my head over this one, but I'm guessing I've got it grounded wrong somehow.

Any ideas?

I might add, there is no rust on this vehicle.

Spdloader

Reply to
Spdloader
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Check the ground from the battery negative to the body. The wire can corrode inside the connector and look OK from the outside. Use a jumper cable from the battery negative to something mounted to the body (horn, starter solenoid).

"Spdloader" wrote in news:a0u7h.44349$ snipped-for-privacy@southeast.rr.com:

Reply to
Red Jeep

Jumper from battery negative to starter relay? I can think of a _lot_ of less hazardous places to put a jumper on.

-- "I defer to your plainly more vivid memories of topless women with whips....r" R. H. Draney recalls AFU in the Good Old Days.

Reply to
Lee Ayrton

Especially since the wires on a starter relay/solonoid are hot.

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The test for rotted motor strap is battery ground (or frame) to the engine block side of the motor mount or somewhere out of the fan and belts.

Reply to
DougW

Here is a good site on how the older gauges work. It is for CJ's, but I believe the early YJ 4.2 was the same.

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This is a Bill Hughes link, the original seems to have gone.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

-- "I defer to your plainly more vivid memories of topless women with whips....r" R. H. Draney recalls AFU in the Good Old Days.

Reply to
Lee Ayrton

My SWAG is that the sender worked fine until you disturbed it and now it is bust, but that's just my SWAG. As you saw when you pulled it out it is just a length of fine wire wrapped around a bit of card. The fuel gauge circuit goes something like this:

[ Gauge ] Sender B+ >---------[ Voltage ]----[gauge]---/\/\/\/\ [Regulator] ^ |----------> Ground

For yours, the higher the voltage seen by the gauge the higher the needle indicates. If the ground is faulty or completely open the gauge won't see any voltage and will just sit. You can check the ground straps from engine to body and engine to frame (the fuel sender gets its ground from the frame, not the body) but I'm guessing that if you haven't seen other electrical problems then chasing the ground won't yield anything useful.

I think that you're going to have to drop the tank again. You'll need to do that anyway if you want to check the ground connection.

Troubleshooting guide:

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-- "I defer to your plainly more vivid memories of topless women with whips....r" R. H. Draney recalls AFU in the Good Old Days.

Reply to
Lee Ayrton

Thanks to everyone! I'll update when I've time to try some of the ideas.

Spdloader

Reply to
Spdloader

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