VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 gas gauge trouble

Driving along this morning and noticed the gauge dropped fron 2/3s to below a 1/4 in about 10 seconds. I filled it up and now it reads a little less than 1/2. Do I need a new sending unit or has the gauge gone crazy? When you turn the switch on the gauge jumps to a little less than 1/2. It must be getting 6 volts, but not reading correctly.

Can the sending unit be removed from inside the trunk or does the panel behind the seat also have to come out?

The 38 manual says drop the tank to remove sending unit. Is that needed?

The fillingstation and chevyofthe 40s has plenty of 12volt after market sending units but I saw nothing about stock units. Any ideas?

I'm no expert, but my guess is the float is bad.
Sid

It must have two,they come in pairs according to the fillingstation list. Cork?

The OEMs have cork floats. I have an extra in the garage. I'll sneak out & see how many it has. It could be the wire on the rheostat broke????

Edit: Two corks, each 1 1/2" long.

The sending unit can be removed from the trunk if you have the original tank. There is a round metal cover on the right side (as you look in the trunk)of the top shelve in the trunk.Take off the cover and the sending unit is right under it....GOOD LUCK....ED

The rheostat is shown in the wiring diagram but the gas tank gauge wire is above the head liner. Where is the rheostat located?

I guess draining the tank and then removing it would be for safety reasons.Working on 18 gals of gasoline with hand tools in the rear of a trunk doesn't sound to smart. I guess if I have to drain 18 gals and do all that I might as well have to cleaned and sealed. Gheeez

What, do you think you still have the original tank in the o' tub...? I would not go with cork, not that there's anything wrong with new cork but I wouldn't put the old one back in...It appears you'll have to remove the unit to test...

Steve the rheostat is inside the tank on the side of the unit.
Look for the round cover I told you about.....ED

This is what the OEM sending unit looks like the float turns the vertical shaft which moves the 'brush' against the rheostat coil. The rheostat is in the head of the sending unit. You DO NOT have to drain the tank. I've had mine out a few times and never drained it, except for the very first time when I had 20 year old gas (varnish) to get rid of.

I see the round cover.


Before/after photo






This might be a winter project.I'm going to drive most of the gas out then drain the tank,then remove it. Call me chicken but working in the trunk with tools on a open container of 18 gals of gas sounds dangerous. It probably needs cleaning.sealed anyway. I drained it once just to see if anything came out that didn't look good, but was surprised when it appeared clean. One spark and me and the ole 38 will be in that big junkyard in the sky.

Thanks for the help. I still would like to find an orginal replacement sending unit, or rebuilt. I don't want to do this but once. Also the new wire going to the gauge won't be above the headliner !! I'll just have to risk a point deduction at the next big carshow...giggle.

The cover Ed's telling you about is left center in the pic below. The only tool you need to remove the cover and sending unit is a slot head screwdriver. No sparks.

Thanks Tiny. Is the wire connected to that large nut or is that some kind of adjustment?

Thanks again to you and Ed.

That's the terminal where the wire connects. I guess my previous post was wrong, you'll also need a 3/8" wrench for the nut. Have something handy to clamp & hold the wire end. If you're not careful it'll fall down the hole and then you'll be pulling the trunk floor panel to get it back. The top of the tank is REAL close to the bottom of the floor panel, not a lot of room for wire fishing if you drop it down the hole.

Thanks for the warning . That's the wire I want to replace anyway. It's one of two that did not get replaced due to the hard location. Wonder why it has such a LARGE nut for the connecting wire?

Below is a photo of the gas tank (two years ago). I think everything was pretty much orginal. Thank goodness the car looks better than the old photo now. Does this look like your tank?

That's not your gas tank. You tank is inside the car under that trunk floor board. You'll have to remove that board to remove the tank. The picture below is with the seat, the board behind the seat and the floor board above the tank removed. The wire you see is the wire to the sending unit that will disappear under the floor board if you drop it.

I'm having the same problem with the gas gauge in my '37 MD. After reading this post I checked the manual I have and it says that the Business Coupe and the Sedan Delivery have the same access panel but it doesn't mention if the other passenger cars have this panel. Does any one know if the '37 MD has this access panel ??

Which Master Deluxe? The sedan, the club sedan, the town sedan, the coach or the coupe?

By Joe you're right. Where I drained the tank is actually a valve in a hole in the rear pan area.This job is getting bigger and bigger,I'll have to remove the seat and wood behind the seat to get to the gastank as well as remove the floor of the trunk.
The wire you keep speaking about...did you replace the old wire above the headliner when you rewired your car?

I would guess they would be alike. There isn't any difference in the trunk of a Master vs a Master Deluxe is there? Someone with a MD will chime in.

You don't have to take the seat out, I was just pointing out for clarity that mine was out when the picture was taken. You will have to remove the trunk floor board. The MD coupe has the tank in the car but I think Gene has said in the past that the sedan's tank was under the car. If I'm remembering wrong Gene I apologize for the mis-quote. The poster didn't identify which MD he was asking about. I don't believe it's a one size fits all.

And here's his answer.

Steve..You don't have to remove the seat or the board behind it you just have to remove the shelf board in the trunk, than take the outside rubber grommet (two piece) off the filler neck (tank & filler neck is one piece). Then wiggle your A** under the car and unbolt the two straps that hold the tank down these are connected to "T" bolts that go through the floor.They should have thin rubber strips between the tank and the straps.. Next wiggle the tank loose. There should be two donut looking padding things on top or bottom of the tank that keeps it from moving around (Tiny did a great post on these awhile back on how he made his own)
I replaced my tank last fall with a Stainless steel one...Big bucks but it sure took allot off my mind because I was having trouble with rust flakes...If you decide to do this also Talk to me first there is some things you should know about my experience with this installation...Good Luck...ED

http://www.parts123.com/parts123/yb.dll?Parta~PartSort~A2~cadefefx~~~~A50~A1


Which one of these sending units look correct? All three are listed as working on a 38 chevrolet. I'd love to replace the entire unit.

One is 90 ohm and the other two are 30 ohm. Sorry the url won't copy/paste

Fillingstation gas sending unit

Hello Tiny,

I'm not sure of the difference between the sedans. I can only tell you that it is a (4) door Master DeLuxe.

Thanks.. I've got that saved . Thanks again.