• Welcome to For E Bodies Only !

    We are a community of Plymouth Cuda and Dodge Challenger owners. Join now! Its Free!

Fuel Sending Unit Works Outside of Tank But Not In the Tank

money pit

Well-Known Member
Joined
Nov 17, 2017
Messages
505
Reaction score
62
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
 

69hemibeep

Well-Known Member
Joined
Jul 20, 2018
Messages
81
Reaction score
13
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
 

money pit

Well-Known Member
Joined
Nov 17, 2017
Messages
505
Reaction score
62
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
 

tonysrt

Well-Known Member
Joined
Mar 12, 2017
Messages
560
Reaction score
152
Also make sure your tank is grounded. Gauge won't work without ground.
 

money pit

Well-Known Member
Joined
Nov 17, 2017
Messages
505
Reaction score
62
Also make sure your tank is grounded. Gauge won't work without ground.
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
 

gs73rallye

Active Member
Joined
Jul 8, 2015
Messages
37
Reaction score
12
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.
 

tonysrt

Well-Known Member
Joined
Mar 12, 2017
Messages
560
Reaction score
152
On the sending unit, the metal ring that holds it in place should ground the unit. But use that metal strap on the fuel line also.
 

money pit

Well-Known Member
Joined
Nov 17, 2017
Messages
505
Reaction score
62
I have the sending unit grounded directly to the battery. I found a modification on one of the other forums. I soldered a wire from the piece that holds the float to the pick up tube. Thanks for your reply.
 

tonysrt

Well-Known Member
Joined
Mar 12, 2017
Messages
560
Reaction score
152
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.
 

money pit

Well-Known Member
Joined
Nov 17, 2017
Messages
505
Reaction score
62
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

Well-Known Member
Joined
Jul 26, 2020
Messages
71
Reaction score
26
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.
 

340challconvert

Well-Known Member
Joined
Feb 13, 2011
Messages
5,177
Reaction score
2,707
Location
Parsippany, NJ
For what it is worth; pics of my original tank and ground strap;

IMG_2808.JPG


IMG_2807.JPG


IMG_3006.jpg
 

Tactical185

Well-Known Member
Joined
Jul 26, 2020
Messages
71
Reaction score
26
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
 

money pit

Well-Known Member
Joined
Nov 17, 2017
Messages
505
Reaction score
62
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
Thanks. I'll check it out.
 

gzig5

Well-Known Member
Joined
May 10, 2018
Messages
393
Reaction score
131
Location
Mequon, WI
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
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

Well-Known Member
Joined
Jul 26, 2020
Messages
71
Reaction score
26
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.
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

Well-Known Member
Joined
May 10, 2018
Messages
393
Reaction score
131
Location
Mequon, WI
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.
 
Back
Top