I have a 70 Barracuda. My gas guage reads a quarter to a half a tank after I fill up. Up to this point it was working fine. I tried replacing the sending unit (an OER unit). The same thing happened. I have a ground to the sending unit, directly from the battery. I tried both sending units outside of the tank, both seem to work fine. When I place the units back in the tank, they read the same as before. I checked the sending units with an Ohm meter, it's within specs. I know the guage works, I grounded the lead, it pegs the guage. Could there be something in the tank that is interferring with the sending unit? I read about the same problem on a number of forums but no difinitive answer. This is driving me crazy. Thanks
Fuel Sending Unit Works Outside of Tank But Not In the Tank
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69hemibeep
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See if you are getting a full 5 volts past the limiter on the cluster. I had two from Redline that were 4.5 volts which equaled almost 1/4 tank
I'm not familiar with the limiter you are speaking about. Where is it located on the cluster? Also, could my temp gauge be causing this problem? I read in a couple of forums that sometimes the temp and gas gauge have problems at the same time. I'm not using my stock gauge. Electrical issues isn't my thing, that's why I'm getting frustrated. Thanks again
I have a ground directly to the battery. I check to make sure I Have a pulsing voltage at the wire that connects to the sending unit. Thanks
69hemibeep
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You figured out the limiter I see. I like these the old style failed and smoke my fuel gauge
https://www.rt-eng.com/rte/index.php/RTE_limiter
https://www.rt-eng.com/rte/index.php/RTE_limiter
gs73rallye
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Not sure if you have this fixed yet, I see it's a month old. There should be a ground strap that goes from the sending unit, to the fuel line on the body. The gas tank does not ground the sending unit. The rubber o-ring isolates it.
Did that wire solve your problem? There is a grounding strap internally in the sender. Check continuity from the top flange to the rheostat to see if you have very low resistance. I find it hard to believe 2 senders would have the same problem. But of course in this day & age with import quality being suspect anything is possible.
I guess the issue with the fuel sending unit is a common issue. The modification that was on one of the other forums said that the sending unit is grounded only in one place on the rheostat housing. So although there may be an internal ground strap, it may not be good enough. It looks like the modification worked. It was actually the more expensive OEM unit that I had just replaced, that failed. Thanks for your input.
Tactical185
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I’m having the exact same problem with my 71. The unit works fine out of the tank, put it in the tank and it only shows 1/2 tank when the tank is completely full.
Were you able to solve the problem and what was the fix? Please help, thank you.
Were you able to solve the problem and what was the fix? Please help, thank you.
340challconvert
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For what it is worth; pics of my original tank and ground strap;
Tactical185
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Just for info, I had the same issue, purchased one from classic industries $99.99 + $15.00 shipping. Nothing but headaches, would only show ½ full when the tank was completely full. Remove it from the tank and it worked perfectly, install back in the tank, and would not work.
Searched amazon and purchased this for $62.00 w/ free shipping. Installed in the tank and it works perfectly. The sending units from CI are suspect?? Just my opinion and experience.
https://www.amazon.com/gp/product/B000C7QJJM/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Searched amazon and purchased this for $62.00 w/ free shipping. Installed in the tank and it works perfectly. The sending units from CI are suspect?? Just my opinion and experience.
https://www.amazon.com/gp/product/B000C7QJJM/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Rapidfire
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That's the same one I put in mine over three years ago and it still reads perfect!
I ended up soldering a wire from the pick up tube to the thermostat housing. And running a ground wire to pick up tube where it exits the tank. So far so good. Thanks for the pics.
Thanks. I'll check it out.
gzig5
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Does this one from Amazon read linearly from full to empty? The one that I got with my new tank reads full when full and gets to E with more than half a tank left. I guess I should never run out of gas, but it is bothersome.
Tactical185
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If I understand your question right, the one that I got from amazon and CI both read the same. From empty to full. I spent 2 weeks messing around with the one from CI. Worked great out of the tank. In the tank would only read 1/2. Wasn’t a ground issue or anything. Called CI and they sent me a new one with no questions asked. When I received it, they sent me the wrong one.
Nothing against CI, I like them and I bought most of parts from them.
I checked amazon and they had one, I received it in 2 days. Installed it and the thing works perfect, free shipping and the cost was a lot cheaper.
Hope this helps
gzig5
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Yes. Apparently it is not uncommon for replacement sending units to not read correctly or linearly through the complete range. Sounds like you stumbled on one that does.
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