VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1938 Master Fuel Sender

I had the fuel sender from my 38 Master restored by the John Wolf company about three years ago. It now appears to be going bad again. I wonder if anyone else has had a similar experience. I am wondering of the restoration involves cleaning/resurfacing the original pot and it just returned to the state it was in.

I was lucky enough to find a pair of working units on ebay a few years ago. What is yours doing/not doing?

When I first got the car the gauge would register somewhere between empty and a quarter tank. I had to jerk the car with the brakes (when nobody was nearby) to get the gauge to register the proper reading. It would stay there for a few seconds and then drop down. Before I sent it away I tested it with a meter and it was very unreliable. Now it is starting to act the same way.

Do you still have cork floats or did you change to copper? Age is hard on the cork and ethanol is extremely hard on the cork...

Appears that the resistance wire is corroding. Also could be corrosion on the contact button.

Chevs of 40's has 1938 fuel sending units for $25.00. The Fuel Station has a couple fuel units that would also work, plus a very good technical article on fuel gauge testing.
I replaced my old, rotted sending unit in my 40 Master Deluxe with a new one and it works great. I would make sure to ground the unit to the body.

Good luck
Curt

cskennedy1,
so the units that they are selling for a 38 are the universal ones and you have been quite satisfied with yours? I was thinking that I should replace it with one of those as they would have modern materials in them. I believe as mentioned above that the contact elements are corroding.

Before I found my units on ebay I used an aftermarket universal that I bought through CoF. It was tight enough that the float arm wouldn't rise or fall because the float arm was too short after adjusting it to work in the shallow '38 tank. I ended up making my own float arm out of a clothes hanger with a longer leg to hold an extra float. That provided enough lift to make it rise but not enough weight to let it fall. I then added a fishing sinker to the arm which provided enough weight for it to fall. It worked fine for a few months until I found the OEM units on ebay and installed one of them. When I removed the universal unit it had worked enough that it finally loosened up and the extra stuff could be removed. I ended up selling it to someone needing a sender. As a side note my OEM sending units have the cork floats and so far (knock on wood) I've not had any issues with ethanol gas degrading them.

Tiny, that was a very inventive approach! You were also making your own version of leaded gas with the sinker!

Old216,
Yes. My fuel sending unit was from Chevs of 40's. It was the universal one. It came with excellent instructions on how to measure the arm length for your particular tank and etc.
I have had zero problems with it. Just make sure you get a really good ground on the sending unit. As stated previously, I took the advise from others to add a separate ground wire from the unit to the frame.

Also, if you decide to use one of these new sending units, it's a good idea to hook everything up (power and ground to unit as though it's in the tank) and simulate the float action by moving the float arm from the 0 ohms position to 30 ohms position over and over again while looking at the fuel gauge. The gauge should go from empty to full and vice verse. This will help to insure the system is functioning as it should before installing the tank and filling it with gas. I only wanted to do this nasty job once!!

One more thing. Make sure the fuel gauge (there is a copper contact area between the 2 poles on the back side) has a good ground. If the fuel gauge housing or backside of the fuel gauge has rust, paint or other crud, you'll have a poor ground. If it doesn't, it will act strangely. My fuel gauge actually moved below empty when I moved the fuel sending unit arm up and down.
My problem was paint between the gauge and the housing. I restored my instrument cluster and the new paint was preventing a good ground. (This is on a 1940 Master Deluxe Sport Sedan.)
After scraping paint here and there, I finally got it working.

Curt

Thanks for all the information, I really appreciate it.

I agree with Chipper that there is probably some corrosion or oxidation on both the face of the wound rheostat wire and the moving contact on the float arm. I typically clean mine by buffing them lightly with a scotch-brite pad and spraying them with contact cleaner, You do have to take the unit apart to do this.

If you got 3 years without a problem you did pretty good. The oxidation is always happening. Unless you drive the car a lot and let the gauge work through its full range, the oxidation will not be wiped off and will continue to build.

One other possibility is that the spring which keeps the contact against the wire on the rheostat is weak or has broken.

The guidance here about aftermarket units is good. Just make sure you get a 0 to 30 ohm unit.

I meant to say "if it does (have a poor ground-rust, paint, etc.), it (fuel gauge)will act strangely.

Sorry for the confusing sentence.
Curt