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Old 08-08-2009, 05:37 AM
aaa aaa is offline
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Fuel sender "dead spots"?

Thanks to this thread, I've cleaned out my fuel sender in my 82 240, and it kinda sorta works now. The shaft was rusted, and I managed to sever the reserve wire while sanding it...

Anyways, I tested it by hand, it behaves oddly. The 1/2 to full range functions smoothly, but a little below 1/2 the needle starts being very fritzy, bouncing all the way to the bottom, and staying there more often than not.

Any ideas on what causes that? I get the feeling that when my tank goes down below 1/2 the guage will become useless.

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Old 08-09-2009, 12:56 PM
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Old 08-09-2009, 01:21 PM
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Mine does that too, about 3/4 it goes nuts, then a little under 1/4 it goes crazy again. I'd imagine its due to bad contacts on the sender that vary the resistance, or to fungus (I had a problem with fungal infestation a while ago) that has built up on the contacts. I'm not sure how to fix this since it is in quite a harsh environment for something like contact grease.
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Old 08-09-2009, 04:05 PM
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Take the sender apart (if you don't know how, follow the instructions in this thread). Very carefully inspect both of the wires that run the length of the sender; these are resistance wires and the action of the float creates a variable resistance that makes the fuel gauge respond. If these wires are oxidized then the sliders in the float won't make good contact. The slider itself can also have oxidation problems but yours sounds more like the wires. Be gentle! I recommend 0000 (quad-zero) steel wool. Take your time. You should be able to feel the difference between the oxidized and non-oxidized sections. This might have been caused by water in the fuel. Don't leave any stray bits of steel wool to cause short-circuits later. Check the low fuel switch contacts while you're in there. Make sure the center rod is smooth so the float will not stick. Put it back together and re-install.

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Old 08-10-2009, 03:18 AM
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Mine did this when I got it. Below 1/4 it would jump between R and the actual level. I tried a bit of biodiesel and after that it stopped. Clogged up my filters, so I think it was covered in gunk.
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Old 08-10-2009, 06:42 AM
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My sender was going all over the place. It was pretty much reading empty on a nearly full tank of fuel. My problem was a mix of two things. A bad cluster ground AND a dirty sender.

Once I cleaned and repaired both it started reading more accurately. It bounces occasisionally when it is in the middle, but when I start the car up it reads the tank perfectly.

I'm glad I got this fixed. I certainly don't want to have to guesstimate the amount of fuel in it!
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Old 08-10-2009, 08:09 AM
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On my 91, gauge operated fine down to about 3/8 of a tank, then started bouncing between R and actual amount in the tank. However, over the course of five tanks of fuel, operation has improved considerably....doesn't do it nearly as much. PO hardly drove the car at all (elderly woman), so I'm figuring fungus or something had built up.

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