Fuel gauge issues

[Cleveland39]

I bought my '39 standard back in November and thought I had found the goose that laid the golden egg because the fuel gauge always showed full. Recently, fear of being stranded on the side of the road with an empty tank brought me out of my fantasy world.

I have tried measuring the resistance on the float. The older looking float was in the tank. The newer looking one came in the box 'o' stuff with the car. I am assuming (I know) the newer one came with the Dolphin gauges and was not installed due to the difference in the mounting plate. I tried connecting the wire to the newer float and when I turned the ignition on, the gauge still goes to full, regardless of the float position, just as it did with the old float. I don't have any instructions or diagrams for the Dolphin gauges, so I don't know what the resistance should be for different levels.

Can someone please steer me in the right direction before I replace the sending unit with a lit match?

[TJ]

They make adapters that go from the old tank to the new sender. I think that Yogi's in Iowa may have the adapter.

[Zeke3]

That new sender looks really long for the tank, where is the arm located when it is in the down "empty" position? Is the depth of the sender adjustable? As TJ says, you should be able to find an adapter for the sending unit.

Also, you might want to consider rewiring your car, the wiring in the picture looks questionable.

[Flathead Fever]

It looks like the sender looks adjustable. the resistor slides up and down on the bar and you just trim the bar off to fit the tank. Trim the bar so it can reach the bottom of the tank. Adjust the sender to the same height as that other one. That will give you a starting point, you may need to move it up or down before you are done.

Normal fuel gauge goes to full if you remove the wire from the sender and ground it. They go to empty when the wire is disconnected. That would be the first thing you need to check. If it goes to full with the wire disconnected, it is either wired wrong or the wire is grounded somewhere. And like Zeje said get rid on that wiring mess. Especially those bluse connectors that pierce the wires so you can get power to another wire. They cut through the existing wires and break the stands and even they don't break them they are a poor connection. Trailer rental companies use them to quickly wire up the lights when they rent trailers. They open up the insulation so moisture can get into the wire, really bad idea especially under a car where they are subject to road moisture.


You don't need to know the resistance points for empty, half and full on the sender. You need to know the depth of the tank and the length to make the float arm si it is able to reach the bottom of the sender and the top of the senders arc. You can start by marking the angle of the float arm when the gauge is on empty and full by hooking the wires to it outside of the tank. Mark the angles with a Sharpee. I suspaect that float arm might come off of the sender so you can trim it shorter Then measure the depth of the tank and trim it so the float will be on the bottom of the tank when the resistors' angle is at empty. THis will take some trial and error adjusting the height of that resistor and the length of the float arm. A lot of guys make carboard templates of the tank height and just hold the sender at the top of the cardboard and operate the sender while wired up. That will tell how much to move the resistor up and down and how much to shorten the float alarm. Just don't cut until you are sure the gauge works right with the float at the top and bottom of the tank. Cut it a little long so you can slowly makes adjustments to it.

[40cpe]

I would first disconnect the sender wire completely and isolate the connector from ground. If the gauge still reads full, you probably have a grounded sender wire. If it goes to empty with the ignition on, investigate your sending un it.

[Ggmac]

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Is your car 12 v neg ground or ...? If its still pos ground thats why the replacement sender may not of been used along with the different mounting issues . Your gauge needs to have a good ground as does your sender , both having same ground . As stated it looks adjustable for depth and float arm length. I have instructions but am currently trying to tie everything down for nasty weather plus Im expecting my new project (46 ford ) from Missouri.
If you’re in no rush Ill dig them out on sunday .

[Ggmac]

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