VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1940 gas gauge fun

Hello everybody,
have to learn more about the functional connection between fuel tank sender and gas gauge in dash.
1st: My 1940 runs perfect and wonderful, made about 4000 mls without any trouble since I did register it in April. What a wonderful car!

2nd: Everything seems perfect, but the tank sender maybe not.
Full is full, the gauge shows full. I fill up, drive, drive more, some hundred miles, and when it shows half I can fill up close to 16 gallons, that means if I see half on dash gauge I must fill up and it is easy mathematics to calculate I did reach the gas station just with the last drops.

I took out the tank sender and did check it in my electronic cabinet downstairs and it is 90 Ohm in "full" position and 30 Ohm in "empty" position. Comparing that with my previous 1931 I remember the 1931 had close to zero (means 0 Ohm or shorty) when empty.
I guess my tank sender does not give out the correct signal in empty position.
Btw: The dash unit is brand new, an ebay NOS part.
Am I right?

Regards
Stefangermany

Stefan,
It would seem, then, that the sender is kaput. Give it a decent burial.
Charlie

Stefan......I would assume that your "old car" (the 1931) was still a original with a 6 Volt electric system..If this is so than your 6 Volt fuel sending unit should have read 0 Ohm on empty and 30 Ohm on full.

I think your 1940 tank should hold 14 Gallons..U.S.
If you have a 12 Volt system in your 1940 then you need a sending unit made for 12 Volts....A 12 Volt sending unit when tested should read 90 Ohm on full....And I would assume it should read 0 Ohm whem empty...Also Make sure the sending unit is grounded well or it will read "Full" all the time...Good Luck....ED

I don't want to be argumentative but I don't think 12 or 6v would make any difference with the sending unit. I converted several vehicles to 12v and never once had to change a sender because of the additional voltage. If the sending unit that's in it is a 90 ohm sender and he still has a 30 ohm gas gauge it'll never read right. He'll either need to put an original 30 ohm sender or a 90 ohm gauge in it for it to read right. Least wise that's the way my senior gray matter sees it.

Tiny you are right...I agree. I just did not describe it right about the dash gauge would have to match the Ohm of the sending unit...I think his 1940 has been converted to 12 Volt....ED

Gas tank capacity on the '40 is 16 gallons.

Why did you replace the dash unit? Does the sending unit drop all the way down freely? If it drops all the way down, and you still have 30 ohms reading, I'd say it is probably shorting out about half way through the coil. Is this a recent problem, or has it been doing this all along?

Hello, to go a bit more into details:
I got my car in Jan.2011 from US and it was 6Volt with a dead battery. I didnt make any experiments without battery, I began to convert the car to 12 volt because there was no chance to register it with the original headlights. That was another topic, long ago.
So I converted to 12 Volt and I did use a small selfmade electronic device converting 12 Volt to stabil 7,5 Volt to feed the fuel gauge system. So the system gets the correct current and should work. I had to replace the dash gauge because the original one was damaged and did not work in the right way, even after repairing it. So my dash unit works ok, the sender arm is free and works, the sender and the tank is well grounded, I have just to know is 90 Ohm full and 30 ohm empty correct or not. If I want to order a new one at filling station I must decide between 30 ohm and 90 Ohm and I dont want to order the wrong part. Packages over the ocean are always one way packages, the complicate customs stuff cannot get reversed. I can only junk away the wrong part and order and pay again.

My tank unit shows 90 ohm if full and if I move down the arm slowly it gets less ohm more and more and ends with 30 ohm in empty position.
Next is the unit is not gasoline tight. If I fill up (overfill) until last drop in filler neck it begins to drop under the car and I loose gas until I drive some miles and the filler neck gets empty, that will stop the dropping under the cdar. It comes out at the tank sender unit. The rubber there is new, so it must be the sender unit itself beeing untight.
Stefan

Stefan, assuming your NOS gas gauge is 30 ohm (it should be) you need to buy the 30 ohm sender. The sender on my '38 weeps a bit too so I never fill the tank unless I'm preparing to drive a distance.

Comparing the pictures at page #339 in the filling station catalogue I guess my car has the wrong sender. My sender looks exactly like the 1950 to 1954 unit which is FS-843 in the catalogue. Maybe this is the reason why my gas gauge does not work well. But: Since weeks we have only rainy weather and my car is just waiting for sunshine, I have no hurry to repair my gas gauge system. I know half on dash is empty in real and my drive without ending with empty tank anywhere in nowhere.

Stefangermany

Stefan,

According to my parts book, the part number for the sending unit is: 1516182. It is right for all except the 1940 models: Business Coupe, Coupe Pickup and the Sedan Delivery.

The part number above is not listed for any other year.

Either the Filling Station or Chevies of the Forties or Ida's should be able to match the part number to the vehicle and their inventory so that you may order the proper unit.
Good luck,
Charlie

BTW: If you happen to see either singers Francine Jordi or Helene Fischer, tell them "Hi" for me. Both are great voices. I like Francine's "Trane" and Helene's "The Power of Love" best. And, they are beautiful, to boot.