Jumping gas guage fix?

When I bought my '54, it had been sitting for a while. One of the first things I did was to replace the gas tank. I bought one of those fancy new poly tanks, and a new sending unit. I figured it was the greatest thing since sliced bread, and that I would never have to deal with a rusty tank ever again.

Well, I still think that. However, the one thing that I hate about this tank, is that it is not baffled. So when I hit the go pedal, the gauge drops rapidly, and when I stop, it rises. Sitting at a stop light, it bobbles around. I know alot of the late model cars have something in their circuitry that slows down how quickly the gauges react to changes in fuel level.

how do I accomplish this in my vehicle? Is it something that I can build myself with parts from radioshack? Surely I am not the first person to have to deal with this...

 

I have the same thing in my 32 so I'm curious about what can be done if anything.

 

The problem is that the oil that dampens the movement is long gone. That and a tank that sloshes around a bit will cause the pointer to jump all over!
Mark

 

I'll probably have rocks thrown at me for this... Use an Auto-Meter oil filled gage...

 

The Stewart Warner I put in my Comet does the same thing.

 

No jumping around with my fuel gauge, the needle doesn't move from 3/4 full. It's ALWAYS on 3/4 full. ........ Should get around to fixing that.

 

You can baffle the tank after the fact using "Baffle Balls" or whiffle balls. We use Baffle Balls in poly chemical tanks in my business and they are 15" diameter and designed to drop into tanks with 16" manways, but you could likely get small whiffle balls through the sender unit opening and accomplish the same thing. Some of the rock crawlers use whiffle balls to baffle their fuel cells.

 

You must have to jam an awful lot of those in the tank to have any affect. How much does that cut down on the tank fuel capacity? It also seems like they would interfere with the sending units normal operation.

 

On my 69 Impala convert there was a can stile pickup with the sending unit inside, Never seen one like it before this,,, What a "Bitch" to rebuild.
Come to find out that with out the can my gage would jumped all over the place with the new replacement unit. Works good now,,,, So far..

 

I would also think they would interfere with the movement of the sender.

But, real reason Im actually posting on here is to ask, how would you determine that the whiffle balls are made from a type of polymer plastic that the gas would not dissolve?

 

That is a terrible idea! The gas gauge sending unit on his Chevy works because a float raises an arm up and down - as soon as you add an object to the tank you are begging for the sending unit and the wiffle ball to get together and render the gas gauge useless.

I have a poly tank in my '53 and the gauge does not jump around. Did you use your original sending unit? If so, pull it out and carefully clean the rust and crud off of the little wires wound around the shaft. Anything on there will interfere with the signal. (I know this because MY gauge was jumping around a lot after I changed my tank. Cleaning the residual crud off of the sending unit or replacing the sending unit should fix it.)

 

Its a brand new sending unit as well.

 

And I am running a stock dash, so changing it out for an aftermarket fuel gauge is not much of an option.

 

Huh. Do you have a good connection from the sending unit to a ground? I can't think of anything else that would cause that problem.

 

We had a similar situation on a client's '53 Chevy....We ultimately installed what I would describe as a sending unit inside of a 2" cylinder. The cylinder would keep the sender very stable, and keep it from bobbing around as gas sloshed in the tank. It was the only car I ever had to do that with, but somebody makes that whole unit just for what you described....

 

http://www.freepatentsonline.com/4838082.pdf
here is a circuit i came across to do that, but you would have to find some one to give you some ball park figures on what resistors and diodes and what not to use. It was assigned to chrysler in 89 so maybe they used some thing similar that you could bogart out of a car.

some older guages used bimetalic strips to buffer the signal. the AC guages had two coils clocked at 90 deg.

Checked my old motors manual, and the buffer on the AC guages is "a calibrated friction brake included in the tank ..." so I'm guessing some sort of friction device mounted to the sender which is why your new sending unit makes the gauge erratic.