Single wire fuel sending unit?

[bluebanshee]

I'm currently running an aluminum fuel cell with a 0-90 ohm single wire sending unit. The gauage works great.... just in reverse. I've read on here that others have had the same issue but all of those that I read were two wire sending units so the wires could be reversed. My truck did not have a gas tank under it when I purchased it but rather a newer style one in the bed. Unfortunately I scrapped that one and the gauge that worked correctly. It appears that the gas gauge is isolated so I tried swapping the 3 terminals on the back of it but the gauge didnt even move when I tried that, although I could have had a bad connection. Not sure what I can do here. This is something I've been living with but I'd like to fix it properly.

 

I did see elsewhere that Mopar is 73-10 ohm up to 1986.... this would explain why my 0-90 works in reverse. If thats the case, I just need to figure out what ohm sending unit I need (I've searched on here).

Edited June 4, 2019 by bluebanshee

[MBF]

I'm gonna make a guess here and say that your float arm mechanism is on the wrong side of the pivot causing it to read backwards of what it should.  The sender itself is a progressive or variable ground.

[bluebanshee]

I have not taken the sender out but I believe its the tube type so no pivot arm to change? It would make sense that the Mopar show full at 7X ohms, when mine starts at 0 ohm, the fuel needle would be opposite.

 

This is probably what I have as I got the tank form these folks

https://www.rhodesracecars.com/Tube-style-sending-unit--0-90-Ohm--85-Tall_p_12068.html

 

I believe this (70-10 ohm) might fix it:

https://www.rhodesracecars.com/Tube-style-sending-unit--70-10-Ohm--85-Tall_p_12065.html

[Plymouthy Adams]

ok...first...the resistance being high (90) is the indicator of low fuel...and at this point should indicate E and not really below the E mark  this gives you a range of accuracy.   ....when at 10 (you should never ground the wire except to quick check needle movement to full BUT NEVER LET it peg out as ground is zero and damage to the gauge could result) with this 10 ohms you will put the needle on full mark with a slight tolerance above this for gauge protection...if your float lever is within its built in stops...and still reads reversed....you should pull the sender to ensure at lowest float setting you get your 90 and at the highest you get your 10  you may have to remove and reverse the resistor if backwards or at minimum return it with this explanation.....

[bluebanshee]

Update: I installed a 73-10 ohm sending unit and the gauge goes from empty to just over half tank (when full). At this point I'm not sure if the gas gauge itself is bad. I can't recall now if the gauge ever went to completely full. With the 0-90 ohm sending unit a full tank would put the gauge at empty, and near half I was almost out of gas. Not sure if its worth spending $25 to verify with a cheap gauge or not. I suppose I could test resistance from a pin on the gauge to ground?

[B1B Keven]

Take one set of wires off of the fuel gauge. Read across both posts with an ohm meter.

You're looking for something in the 25-45 ohm range. If so, the gauge is good.

[bluebanshee]

Measured 94 ohm across the terminals. Looks like it's bad, are there any oem type replacements? Maybe a new gauge could be cannibalized for the guys?