VCCA Home Forums TECHNICAL - GENERAL Body - Sheet Metal, Paint & Wood First time here

Hi all. I am replacing the fuel tank in my 1950 Styleline deluxe. Should I paint or undercoat the underneath side of the trunk, where the tank goes, before install? Thanks in advance for any help. I'm happy to be here.

Welcome! I'll move this to the Body & Paint forum to get you a wider audience.

Thanks Tiny! I'm looking forward to exchanging info with others.

If you do paint the underside of the trunk you will have to run a wire from the tank to ground somewhere close in order for the gas gage to work properly.

Dick

Thanks Dick! I thought that might be the case.

I didn't know what was done originally. It looks like the might have been some primer or something on the 2 supporting ribs.

If your tank and straps are bare without any paint, etc you might get away with the strap bolts making good enough ground.

Dick

I think I will run a ground wire from one of the sending unit screws to one of the strap hanger bolts. Does that sound reasonable?

That is a good plan. We added a ground wire to my friend’s ‘49 3100.

We put some thin rubber padding in the tank saddles when we installed the tank. We were concerned that the sending unit would not have an adequate ground.

Just make sure that you actually have a good ground where you attach the end to the frame or body.

Thanks Rusty. Appreciate the input.

Now, one other question. Is the sending unit terminal supposed to be isolated/ insulated from the gas tank? Mine is not. Wondering why I would need to ground the tank if that is the case?

The threaded stud on the sending unit should be insulated from the mounting plate for the sending unit. It should be attached to the wound wire rheostat within the sending unit.

If you connect an ohmmeter you should be able to read the difference in resistance as you move the float arm. One wire attaches to the stud. The other attaches to the mounting plate i.e. ground.

The reading should range from no resistance to about 30 ohms.

If you get an open (infinite reading) or zero only the rheostat or wiper arm contact are bad.

Rusty, I have a brand-new sending unit and there is continuity between the center threaded stud and the mounting plate. This doesn't seem right to me. What else can I do? Thanks, Mike

Are you using an ohmmeter to check that continuity? If you are using a test light it will possibly show continuity all the time.

The meter should read zero ohms with the float in the down (tank empty) position.

The meter should read about 30 ohms when the float arm is in the up (tank full) position.

There will always be continuity across the sending unit. The key is that the resistance will vary. The sending unit is a variable resistance unit. The resistance increases as the float arm rises. It is not an on/off switch.

Thanks Rusty. That is starting to make a little more sense to me. I will check the ohms today and see what I get. Obviously not my area pf expertise. I just want to make sure it's right before I install the tank. Thanks again.

I admire your desire to make sure things are working correctly each step along the way. It will give you the confidence to move ahead and save time and major frustration later.

I helped another friend install an aftermarket sending unit into the fuel tank of a '54 Chevy pickup. He asked me to help him troubleshoot things after the gauge would only read empty.

It was a little tricky because the sending unit worked correctly when it was out of the tank and you moved the float arm. It took a while to figure out the problem. The shape and design of the aftermarket unit was such that a portion of the insulated rheostat would short to the tank the way he had installed it.

The ohms on the sending unit checked out. I will install the tank and hope for the best. Any idea on what gage wire I should use for the ground?

We used 16 gauge because it is what I keep for “ad hoc” wiring. 18 is more than adequate if that is what you have. This is a low amperage function.

Great, Rusty. Thanks so much for your help.
Mike

Finally got the tank installed, everything works well, Thank you all for the great input. I t was very helpful. Now on to the next issue!