Fuel Gauge searching/wonky - Defender Source
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  #1  
Old September 15th, 2014, 08:33 PM
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Chris Davis
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Fuel Gauge searching/wonky

Yesterday my fuel gauge started "searching". Goes up, down, all around. Usually settles on what may or may not be right. Gonna have to fix it. Before I start digging, have any of you had this?

My two thoughts are that the gauge's ground wire may have come a little loose--that is the first thing I will check as it is easiest.

Second thought is the sender. This is part of the pump assembly, correct? Been a while since I have pulled it, but I am almost positive it was part of the cage where the pump is. I can't seem to find one of these assemblies as a separate bit--is it?

If I have missed any possibilities, please chime in :-)
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  #2  
Old September 15th, 2014, 08:59 PM
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Jason Lavender
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Had this happen last month...bum ground from the sender was the culprit. Ironically, only seemed to really happen in the rain...go figure. Anyhow, regrounded to the chassis and all has been well since.
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  #3  
Old September 15th, 2014, 09:25 PM
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Yes, like I always say, horses first then zebras.

Check grounding. If that's not it, then fill up your tank, pull the gauge and measure the resistance across the line (should be around 15 ohms or so). When it's empty it'll be closer to 300 ohms. The sending unit is basically a potentiometer and rarely needs to get replaced.
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Old September 16th, 2014, 12:42 AM
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Chris Davis
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Well it did rain the night before.... I usually start with the grounds too. Can you shortcut this for me and let me know where the ground for the sender connection is?
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Old September 27th, 2014, 11:50 PM
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Chris Davis
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Well, as much as I didn't want to, I dove into the tank. Hate that job, but sucked it up. There is a bare flexible wire on the sender that moves on its mechanism. Some,sort of woven wire. Friggin thing disintegrated and only one strand was still there when I pulled it and when it touched it it broke. Couldn't think what I could use for the wire that was flexible until I remembered my desolder ribbon, cable. I'm pretty sure it will hold up well-- so I used it and my problem seems to be solved. Not sure how it will stand up but my guess is quite well...
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Old September 27th, 2014, 11:53 PM
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Only letting me post one photo at a time...
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  #7  
Old September 27th, 2014, 11:54 PM
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Photo of pump/sender
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  #8  
Old January 3rd, 2015, 03:23 PM
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F word! I was just testing all my gauges and noticed that I am at 1/3 when it's empty on the fuel gague. Ohms are like 117. Sounds like it times to drop the tank again and take a look at the sender. I removed the pump and put on a pickup tube for the tdi swap and I thought it was all good when I put it back in. But sounds like it wasn't. Grr.
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Old January 3rd, 2015, 06:07 PM
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Mine's acting up too. Thought I had it fixed, went to Moab and the thing bounced up & down a lot, became stuck on full. Starting acting normal on day 3, now I know it has fuel but it's dropping off to way empty. Maybe it is the ground after all, but it is 18 years old now. Where is the ground point?

I think I solved the dealing with rusty tank skid plate bolts, use plumbers sealant on them. The kind that comes in a can with a brush attached to the lid. I had to re-thread mine to 3/8" bolts, the stock ones were totally stripped out.
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  #10  
Old January 3rd, 2015, 07:01 PM
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http://www.defendersource.com/forum/...ad.php?t=52549

See my thread above for some more background on the flaky ground issues that affect gas and brake lights on the NAS D-110.
Photo enclosed to show the ground point location behind the right rear speaker.
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  #11  
Old January 10th, 2015, 09:25 PM
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peter
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Hey Chris,
Where did you get that ribbon?
I dropped the tank tonight and I just nudged the existing ribbon and all of a sudden it all works. I don't trust this will last long. The existing is realllllly crumbly. Nice to see the range read right though.
I was surprised how touchy the existing ribbon was. I could keep poking at it and get differnt ohm readings.
Thanks,
Pete

Edit: found a bunch on ebay. "Viton" you can PM me your address and I can send you some from my order. I won't need all 5 ft!
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  #12  
Old January 11th, 2015, 09:34 PM
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Chris Davis
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Glad you found some! Any electrical place that sells solder/reaistors should have some, too. It's worked great for me, glad I could give a useful tip!!!
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Old January 11th, 2015, 11:32 PM
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I had bought the least expensive tank pump assm'b (off Ebay & for a RRC about $65) just to obtain the the float as my original had become stuck at the top & read full continuously.

So I replaced the float but I noticed that the fuel level sender seemed different so I assumed the tank shape of the RRC was different than than the NAS 90 hence the difference in the little "tick things" that react in Ohm's to properly register the fuel level of the 2 different shaped tanks. The D90 fuel sender unit says, NAS D90 on the little Ohm resistance board, so I left it in the tank & now it is totally screwing up, dropping off all the way to "way below empty". So something is up with the sender or possibly the ground, though my truck has Zero rust on it, but since the screw by the rear L speaker does screw into the Alum. tub base, maybe that is the problem.

I later saw a reference here in this forum to the full Ohm's vs empty Ohm's on the D90 sender so I checked mine on the unused RRC I bought, and it has the same resistance as the D90, so a swap is in order when I drop the tank.
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  #14  
Old January 23rd, 2015, 01:02 PM
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peter
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Success!
Thanks to Chris for making this easy to troubleshoot.
I got 1.5mm copper wick, but I would recommend getting 1.0 if possible for anyone else doing this. The stock size looks to be about 0.8mm.
I was able to hold the wire in my fingers and roll up the ends to get them through the holes in the tabs.
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Old January 23rd, 2015, 03:00 PM
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I've got my D90 '97 fuel unit out & mine doesn't have the braided wire on it at all nor the soldier point on top of the "pump canister", were the pump was once located. yeah, my unit is different than the pictures in this thread.


No need to send that braided wire to me Bronco
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  #16  
Old May 17th, 2015, 01:06 AM
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Hey Chris, how is the fix holding up?
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  #17  
Old May 17th, 2015, 01:52 AM
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Really good. It has been perfect since I replaced that braided cable.
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