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Fuel Sending Unit help


Mopar Wayne

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Hey all, I just replaced my fuel tank in my 48 D 24 Custom. I went to install my new sending unit and my new unit is a 2 pole sender and my original is a 1 pole. Any ideas on where I can get the 1 pole? It looks like in mid 48 they changed to a single pole design. My car is still 6 volt positive ground. I did some research and found only one reference from 2010 on the forum. Thanks 

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Hi...you can use a universal sender available from Summit for about $20..since fuel senders are not voltage sensitive they work on variable ohms resistance the 6 volt positive ground will not affect it..other than it might read backwards in which case you have to turn the float and resistor upside down. The float has an adjustable arm to accommodate different tank depths..

hope this helps...

Tom

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On many "new type fuel senders one pole is for a separate ground wire as to not count on the tank itself to be grounded. Usually they are marked on the sender. ;) If not make sure both poles are insulated from the mounting plate and use either one as a ground terminal makes no difference as the sender is just a variable resistor to ground.

Run a separate ground to be body close by.

 

DJ

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Hi again...the fuel gauge has 2 terminals ...one goes to ign the other to fuel sending unit ....the ign side has constant voltage, the sender side has variable voltage to ground, the variable part meaning the level of the float...the variable voltage is what makes the needle move...the gauge is grounded through the mounting screws...

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On 3/31/2018 at 5:37 PM, DrDoctor said:

   How many terminals are on the back side of the fuel gauge? Our ’46 Plymouth has 2, and the ground is from one of the mounting screws to a common ground post, which is wired back to the negative terminal of the battery (the car is 6v neg ground). Is there a difference between the gauges on Dodge vs Plymouth? If there’s 2 terminals on the gauge, it seems logical that you’d need a sending unit with 2 terminals.

Hey DrDoctor, thanks for the info.  My gauge has 2 lugs on it. My car is positive ground as well. 

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Update, I ordered a single post 10-75 ohm universal unit from Summit. The gauge still is not reading correctly. I am at a loss. The gauge has 2 posts on the back of it so I am sure it is a single wire unit. With the key on and the wire in the trunk not touching anything the gauge reads empty. If I ground the wire the gauge goes to full. When I wire in the sending unit it goes to full no matter where the float is. Does anyone know if I can test the gauge? I went with the 10-75 ohm resistance unit because that is what I saw on another post. I would think it would read something no matter what. I even took the sending unit and connected straight to the gauge with the same result.  Any ideas would be really helpful. Care is still 6 volt, positive ground system.  Thanks all

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Did you try reversing the leads on the gauge ? If you have a multi meter check the wiring for continuity from the tank to the gauge - might be grounded or something like that. You can also test the sender with an ohm meter to see what the resistance is depending on the arm position...

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1 minute ago, Dartgame said:

Did you try reversing the leads on the gauge ? If you have a multi meter check the wiring for continuity from the tank to the gauge - might be grounded or something like that. You can also test the sender with an ohm meter to see what the resistance is depending on the arm position...

Thanks Dartgame, I did check the sender for changing resistance when the lever is moved. It does vary when moved. I also tried reversing the leads as well, with the same results :( . I am beginning to think the gauge is bad. 

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19 minutes ago, Dartgame said:

What about the wiring from the sender to the gauge ?

It is one wire, and I took the sender to the gauge and connected straight to the gauge with the same result. Plus it's only 1 wire going to the gauge from the front. 

 

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Hi..Ok...remember electricity is really not magic although l have thought so once or twice...let's look at the various checks before we go any further...first...make absolutely certain that both the sender and the gauge are perfectly grounded. I can't tell you how much time and brain cells l have burned chasing similar problems only to find insufficient ground.. a visual inspection is not adequate...got to check with voltmeter or test light.

Ok?  All grounds good! Next check your wire that runs from sender to gauge...make sure it is satisfactory and not touching ground somewhere between sender and gauge. Then check your power source to make sure there is sufficient voltage at gauge. All good?

You mentioned you checked your new sender with ohmmeter to make sure it is operating correctly..l have had new in the box senders and gauges that were defective...Maybe not

likely but certainly possible...your ohmmeter should increase or decrease when you move the float arm.

The next check is the electromagnets in the gauge itself...find the fuel gauge thread with explanation by Plymouthy Adams ...he does an excellent job explaining the entire troubleshooting process and particularly the gauge.

Hope this helps!

Tom

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Hi again...l just reread "50 Dodge fuel gauge operation" by Gregarious...check it out...l also recall a similar problem l had and l wanted to ask if you are doing your checks with the sender installed in the tank or out...observe your gauge with the sender out of the tank ...again making sure grounds are good...see if needle moves when you move float arm..if the needle moves as it should  determine if the float arm is up or down according to needle movement., then make necessary adjustments.

Edited by Tom
Forgot something
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  • 2 weeks later...

Hey all, thought I would give everyone an update - She is fixed! Found my gauge to be bad. For some reason the gauge itself was not grounding. I procured an NOS one from ebay (for a great price mind you) and tested it before I replaced. BOOM, I can now tell how much go juice I have left. I finished up making my sending unit and just finished installing it all. As a side note, I now have a 2 post sending unit for sale, Brand new. Installed to find out it was wrong. So if anyone needs it make me a fair offer. Also, thanks for all the input. This is such a great tool to have. Kudos to you all!

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