jpc647

So the gas gauge on my 72 Cutlass has always bounced a bit. Like going around a corner, accelerating up hill, decelerating downhill. It's especially more noticeable when under 1/2 tank. If talked to a lot of other owners and they all same the same thing.

Is there a way to mediate this? I don't expect it to be perfect, but is there a way to slow the reaction time down of the signal sent from the sender to the gauge. A slight delay would mitigate this. I've had the gauge out before(to fix an idiot light circuit) and I didn't see anything apparent that would do this.


My gas gauge also moves down quicker when under 1/2 tank. I know the aftermarket replacement senders aren't perfect, and I'm okay with that. Maybe these are related issues?

Someone who's good with electricity must have had this bother them too and think up something?

RandyS

What you are seeing is caused by the gas sloshing around in the tank. A tank would have to be well baffled to eliminate the variation you are seeing. Also, the tank seems to empty faster below 1/2 due to the geometry of the arm on the sending unit.

You would have to find some sort of 'voltage averaging' circuitry to even out the spikes.

Fun71

I'm sure you could devise a simple filter circuit with a large capacitor to slow the gauge movement. Since I am very seldom going uphill, downhill, cornering, or accelerating/decelerating for extended periods of time I never was bothered by how much the needle moved around.

oldcutlass

What your describing is normal. All older cars do it. The time to worry is when it stops bouncing.

jpc647

Mine does it more often than that. I mean any corner going around town or on the backroads it'll move. Even during normal driving, coming to s stop for red light in a highway.

It'd even be happy if I could make it index(like only have 16 preset locations the gauge can be at), with some sort of 10 second delay with a voltage change. Sure, pumping gas, the needle might not come up right away, but by the time I hang up the nozzle, and get back into the car, I probably wouldn't notice.


There's a lot of really nice cars on here, I'm sure someone has thought about this.

Oh I understand that. But I'm thinking someone might have improved it. Maybe not. I just got to thinking yesterday, and thought it'd make a thread and see.

oldcutlass

Nope, it is what it is unless you invest some money in a new tank and better gauge circuitry.

jensenracing77

These cars did not do that new and none of mine do it now..... How bad does it bounce? If it is really fast it is likely the gauge itself. It can also be the sender in the tank is bad from the float not making consistent contact with the coil. I have also had a loose ground do it.

Edit... Yes they do a little when new but it is a slow movement, I am talking about the bounce that is doing it much faster than the little sway that take several seconds to do one way.

2Olds4U

jpc647, if you're looking for a cheap work-around, this may help:
Older VW Beetles had the same problem. VW installed a "vibrator" mounted to the speedo to cure it. All it was was a dome light bulb ( like a Sylvania 6411) in a little box mounted in the line just before the fuel gauge. It made the gauge less erratic.
If you wanted, you could probably mount one right at the tank with no modifications. Not sure how it would hold up under the elements though.

Like this:

http://www.ebay.com/itm/like/2616925...&ul_noapp=true

jpc647

Maybe bouncing is the wrong term. The gauges just moves around a lot. If I brake more than very gently, it'll move. If I accelerate enough to keep up with traffic, it moves. Sometimes it's only 1/16 of a tank, but sometimes, it'll go down more than 1/4 tank and come back up(accelerating or cornering).

It's not really a slow movement, it moves quick, then comes back to normal rather slow(approx 10 seconds).


Interesting. Thanks for the link!

MDchanic

That does sound normal.

The gauge is already designed to be slow-responding, to eliminate rapid fluctuation from sloshing, but it is not designed to damp variations longer than a few seconds duration.

I'm sure you could design an electronic work-around, but then wouldn't it be better to design a work around for the fact that 3 points past F is Full, "F" is ¾-full, "½" is ¼-full, and "¼" is "Fumes"?

- Eric

jpc647

Yeah, I figured it was pretty normal. I just, I've been driving the car a lot more lately, and it sort of got on my nerves, especially when a friend asked me about it. So I thought maybe someone wired in some sort of delay, and it was common knowledge.

Your gauge is skewed that much? Mine will actually go above full, and below empty. I don't know how much below E, but I do know I drove 36+ miles on E. I left my gas cap keys at home once a few years ago, and drove 55mph on the highway all the way(maybe I got 14mpg instead of 12) and I made it home.

RetroRanger

Lol when mine says E it means it!! Found that out the hard way twice this year!!

MDchanic

"If all of your friends were jumping off the Brooklyn Bridge, would you follow them?" — Mom



Bottom line: I wish.

Not to my knowledge, though.



Sure, and all of the GM cars I've had have been that way, more or less.



In my personal experience, I've found that it varies, even on the same car.
Tends to keep you on your toes.

- Eric

oldcutlass

Again as I stated above, these gauges were never very accurate. As others have stated it tends to follow the contour of the tank. Some drop fast from F to 1/2 while others stay there for longer and drop quickly to E. The time to worry about how much fuel is left is when the gauge stops floating around, the tank is empty.

jpc647

Well I guess my gauge, comparatively speaking, isn't all that bad.

It's something I might experiment with other the winter.

Something like the VW beetle link was what I was thinking, maybe there's a way to make it work.