Dean Parker Posted April 6, 2009 Report Share Posted April 6, 2009 Ok , lets hope that some one here can figure out THIS problem !! For the most part I'm pretty good with my hands, but this is one problem that I can't seem to find any information on. I just bought a 1948 Dodge D-25 4-door sedan, and the Fuel gauge is not working right. When I turn the key on the fuel gauge needle pins to the full side ( no the tank is not full of gas) so I figure that I must need a new fuel tank sending unit. So I bought one from "Roberts" and installed it. And it still did the same thing when I turn on the key, it just pins it's self to the full side. ( by the way, my old sending unit has one wire and the new one also has one wire) So I was thinking that maybe that wire that go's from the gauge to the sending unit is bad, so I bypassed it and ran a new wire from the back of the gauge to the top of the sending unit on the out side of the car just as a test, and still no good, the needle still pins to the full. Now my original gauge has two wires that come from the back of it, One that go's to the sending unit and is marked GA, which I'm guessing go's to the sending unit, and the other that is marked SW, and to best that I can tell go's to the ignition switch. When I turn the key on , my light tester shows that I have power to the SW side of the gauge, but nothing to the GA side. When I disconnect the wire from the back of the GA side or the gas tank sending unit, the needle go's to empty ( just like turning off the key). Ok, now I started thinking that my Fuel Gauge it self mite be bad, so I bought a NOS fuel for the 1948 Dodge, which by the way is identical in every way to my original gauge. So before I installed it I tried to hook it up from just jumping the hot side from my old gauge to the new and running a new wire form the back of the new gauge to the fuel tank sending unit, ( kind of like a test to make sure that that's the problem) But unfortunately I get the same result !!! The needle again (with the new gauge now) pins it self to the full side. Yes...I checked the ground to the sending unit to tank to battery and also checked it with gauge grounded an ungrounded, I even tried just running a new wire from the battery Hot side to the back of the gauge just to eliminate any internal wiring , and still the Fuel Gauge Needle pins to the full side. What am I doing wrong? I see no evidence that it was ever wired in any different way, And I can not find any up to date wiring diagram for this car that show just One wire from the sending unit. Can someone please solve this Problem ! Thank for reading Dean Parker .... Phone 856-655-1830 Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted April 6, 2009 Report Share Posted April 6, 2009 Use the search function on the tool bar above. Fuel gauge repairs have been discussed many times. Quote Link to comment Share on other sites More sharing options...
Dean Parker Posted April 6, 2009 Author Report Share Posted April 6, 2009 So far not finding anything that helps. Quote Link to comment Share on other sites More sharing options...
Norm's Coupe Posted April 6, 2009 Report Share Posted April 6, 2009 This is why a service manual would be an excellent thing for everyone with our cars to buy, before buying any other part for their car. If you have a service manual, your problem is explained in detail (with pictures) and instructions on how to trouble shoot and fix it. It may also be on the main site http://www.p15-d24 on one of those links. Also, by buying a service manual, you will get a detailed electrical wiring diagram at the back of the book. Quote Link to comment Share on other sites More sharing options...
Dean Parker Posted April 6, 2009 Author Report Share Posted April 6, 2009 Do you mean the Blue 1941 to 1948, D-49,22,and D-24 Shop Manual ? Well if you do, then you wound know that it only shows a two wire configuration, not one wire as I mentioned .......Dean Quote Link to comment Share on other sites More sharing options...
Norm's Coupe Posted April 7, 2009 Report Share Posted April 7, 2009 To be honest, all I have is a manual for 1946 - 1954 Plymouth. Have two. One original and one reprint by Crankin Hope. Both of those books shows both one wire and two wire gas gage wiring, and trouble shooting, and how to fix for Plymouth. Also has the wiring diagrams for all those years at the back of the book. That's why I did not answer your question as you have a Dodge. But.....I assumed the Dodge service manual would have all that information, because the Plymouth manual does. After all, Chrysler published both original books. As Don mentioned, there have been many discussions about fuel gages and how to fix. Here's one recent link http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=14279. There has been many others too. If you do a search they should come up. Search for either "fuel gage" or "sending unit". Otherwise click on my profile and click on the link that says, "View all post by Norms Coupe". You'll have to scroll through at least 20 pages or more of post, but you should find other threads on the same subject. Quote Link to comment Share on other sites More sharing options...
steveplym Posted April 7, 2009 Report Share Posted April 7, 2009 A thread I started on this a few years ago. http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=3029&highlight=Fuel+Gauge Sounds like you have your wires connected right. I had to run a ground from under the sending unit out to the frame. That took care of my problem. Otherwise it always went straight to full. Not properly grounded means it will go all the way over to full. If the wire that runs to the switch from sending unit is grounded it will read 1/2 when full, 1/4 when half, and so on. If you haven't run a ground wire from under the sending unit screws to the frame yet try that. Over time with painting the straps and the frame the tank ground can not work. Quote Link to comment Share on other sites More sharing options...
Dean Parker Posted April 7, 2009 Author Report Share Posted April 7, 2009 Steve, This sounds like good information, will try it tomorrow and will let you know how it went. Thank you...all Dean Quote Link to comment Share on other sites More sharing options...
Dean Parker Posted April 13, 2009 Author Report Share Posted April 13, 2009 Okay all, this weekend I looked closer at my Fuel gauge problem,and as I removed the new sending unit from the tank, I noticed that the power tab on the bottom side was bend over and contacting the body of the sending unit and causing it to ground out, making the fuel gauge needle read full all the time. So after I corrected this the needle started working again, only thing is that it was now working backwards, meaning that went I moved the sending unit float up (by hand) the needle wound start to go down, and went I moved the float down the needle wound start to climb up. Try reversing the wires but still the same. So not sure what the problem could be, I just modified the new sending unit by flipping the internals around. Seams to be working fine now. One strange thing though, after I was finished, I went to start the car ( had just drove it five miles before I start working on it) a it wound not fire up. It just cranked and cranked. Noticed that I was not getting any spark, so I replaced the Condenser in the distributor and that solved the problem........go figure. Thanks to all who showed an interest in this thread. Dean Quote Link to comment Share on other sites More sharing options...
steveplym Posted April 14, 2009 Report Share Posted April 14, 2009 Glad you got it fixed Dean. Those fuel gauges are very finicky. They have to be just right to work right. Not sure why it was reading backwards, that is odd. Condenser going out is a bit odd too, oh well all's well that ends well. Quote Link to comment Share on other sites More sharing options...
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