40 sedan original gas guage adjustment

[Gezer]

new sender working but reading high. Tank about 7/8 full and gage reading about full plus 1/8 to 1/4. Can the gage be adjusted?

[Seth Swoboda]

The reproduction sending units are garbage. You'd be better off placing a want ad on here for a good working original. I just picked up a good original 1940 gas tank with sending unit. I have not yet tested the sending unit to see if it is good, however.

[rotorwrench]

Is this an original King Seeley type sending unit or is this one of the late aftermarket type senders? It's common to have problems with accuracy on the late replacement senders due to them not having the same type of electrical function as the OEM KS units. Late repros are rheostat types with specific Ohms reading from empty to full and the OEM units are a variable current draw by heating coil type mechanism. The quantity indicator units don't have provisions for adjustments.

Its kind of a hit or miss indication with the late type senders installed. They generally can be adjusted with the float mechanism for full to empty but that's about it.

[19Fordy]

Gezer, I just spent the last 2 weeks trying to get my 1940 OEM gas gauge to read accurately. Finally got it to read accurately. Here's what I did. Disconnect + battery terminal and switch OFF ignition. Disconnect + wire and ground wire from tank sender. I have a plastic tank so I am running a separate ground wire from sender to frame.

Lay a piece of cardboard on trunk floor and place sending unit on that cardboard so it touches no metal. Stuff rag in open hole in gas tank. Take one wire with alligator hooks and attach one end to power wire that feeds the sender and clip the other end of same wire to input screw on top side of sender. Take another wire with alligator clips and attach one clip to bare metal of floor trunk latch hook and clip the other end through one of the screw holes in sending unit. Make sure all these wires are making good contact and that the sending unit is insulated from the car with the cardboard. Now reattach your battery cable and switch ON your ignition.

Move your float all the way up to the FULL position and check the needle on your gauge. Give needle a chance to heat up and register as the King Sealy units don't operate on Ohms law. It may take a minute, etc.

Then move float its lowest position and check gauge reading. Keep in mind that when your gauge needle is on the E mark you want to have enough gas left in your tank to get you to the filling station. If your fuel gauge doesn't read correctly you can make adjustments by bending your float arm and also by adjusting the star wheel inside the sending unit. I did both since my plastic tank holds 16 gal. not 14 like the stock tank.
Be sure to flip your ignition switch to OFF when you connect and disconnect you alligator clips when making adjustments.

To adjust your tank sending unit, you turn the starwheel inside the unit clockwise to make the needle read closer to the Full mark and CCW to make it read more towards Empty. You adjust the starwheel with a small flathead screwdriver moving it only about 1/32 in. at a time with the tank sending unit clamped in your vise. A brake adjusting tool is used to pry off the top of the sending unit and you can use channel locks to carefully reinstall it.

This entire process is very tedious and you must be patient as you will make incremental small progress each time you adjust starwheel. When you get tired, STOP and take a break so you don't do something stupid out of frustration. I disassembled the fuel gauge but did not adjust it as it is extremely delicate.

Gezer: The first and easiest thing I would do in your case is remove the sending and rotate the startwheel CCW just a teeny, weeny bit and reinstall it to see any differences in needle reading. Also, make sure your float is not cracked or filling up with gasolene. That will effect gauge readings.

Once you get the gauge to read correctly reinstall the tank unit using your OEM wires. It should read the same. If it doesn't your OEM wiring may be faulty.

Even with the original steel tank, I think it's a good idea to run a separate ground wire from your sending unit to your car frame just to make sure you have a really good ground.

Hope this helps. More experienced electrical folks may have a better approach.

[fordor41]

On my '41 I used an aftermarket sender (75-10 ohm) from Yogi's street rod parts in a 17 gal poly tank and stock gauge. Powered via a Ron Francis VR-1 12-6V reducer. E is EMPTY, 1/2 takes about 8 gal & is slightly above F with full tank. Close enought for me.

[19Fordy]

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Wow! It's good to know about that Yogi's unit. I am very surprised it actually works with your stock gauge. I am also using a Ron Francis VR-1 reducer and a poly tank.

[Gezer]

Thanks 19FORDY.
I did the test and found that the original OIA 9275 A sender I have is good but it has a leaky bulb. I patched it with JB Kwik Weld but in checking with JB Weld after the fact, (GRRRR) They said ALL their products with deteriorate in time when exposed to gasoline because of the ethanol.SO... Where would I find a replacement float bulb. The one on the sender I purchased is smaller in diameter and will not work in the larger arm in the original sender.
Can I squeeze the arm smaller without it breaking?

[19Fordy]

Forget JB WELD.
I have had success soldering the OEM leaking brass float bulb. Use a blow dryer or just put it out in the sunlight to evaporate the gas from inside the bulb. Then solder it with 60/40 electrical solder. Very easy to do. You can use the smaller bulb if you use a pair of pliers to make the loop that snaps around the bulb smaller. It's very "springy" metal and won't break.
However, since new bulbs are available, I suggest buying one new. My stock float is 1 3/8 " dia. by 2 1/2 " long. You can buy a new float from C and G. Give them a call to verify what size you need. Remember, be patient.
https://cgfordparts.com/ufolder/cgca...&searchnumber=

[Gezer]

Thanks, Ordered C and G Float

[mike42]

I bought a replacement unit for my '40 Sedan from C&G. I had the same problem in the reading. I just kept bending and adjusting and it finally came out reasonable. When full its just over full mark, but so is my Mercury Milan which is a 2009 model !!

[19Fordy]

Mike, How much gas do you have left when the needle is covering the E?
Enough to get you to a gas station?

[HDowse]

!9Fordy,
Thanks for the detailed explanation on the tank sender/gauge. My wife and I took a short dust off ride yesterday and I saw the gas gauge reading much lower than the gas level I knew was in the tank. I read your post, went after the unit this afternoon and as soon as I lifted the sender out of the tank, I could feel the gas sloshing in the float. I tested the sender as you described and it reads E to F correctly. A new float is on order. Thanks for the help, Hunt.

[mike42]

Fordy.....I'm guessing about 2 gallons, but I really don't let it get real low.When it gets to half full I fill it up.

[19Fordy]

Thanks Mike. I wish you many smiles of happy motoring.