Gas Gauge Bounce

[Frank C.]

How stable is everyone's gas gauge? I have a '67 BJ8 and unless I am totally full, mine bounces all over the place.

 

[catfood]

My '55 BN1 is exactly the same. If I accelerate hard the gauge reads zero, when I break it reads full. I believe the old gauges are not (electrically) damped like a modern gauge so as the sensor bounces around in the tank the gauge echos the effect. I'm sure some of the electrical wizards out there should be able to come up with a suitable damping circuit. Any takers...?

 

[fordhealey]

my 61 BT7 gauge reads about 1/8th when empty and
3/4 when full(up in the pipe) i haven't made any attempt to fix it yet. i am going to check my sending unit wires first, before i pull it. not really sure to how to adjust (bend) it other trial and error.
gregg

 

[CDK]

The gas gauge mechanisim is just a float and arm device that is connected to a rheostat(sp).I think the real problem in it moving around so much is that there is limited baffeling in the gas tank to keep the gas from sloshing around so much.You can make minor calibration changes by bending the float to help with a more full or empty reading.Warning watch for oxidized hold down screws that will want to break off and add to the experience.

 

[droy]

Mine bounces so much that the needle will stick on the full side and I have to tap the glass to get it back.

 

[Larry Campbell]

The bounce may also be related to not having a good ground for the sending unit. Actually the tanks are baffled fairly well, but the ground may be the culprit.

 

[Blonde Healey Girl]

You guys and your gauges.....The whole reason Donald put those noisy electric fuel pumps behind the driver was to let you know when you're running low on fuel. Kinda like the low fuel light on the dash of your daily driver econobox.

 

[John Turney]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Blonde Healey Girl:
You guys and your gauges.....The whole reason Donald put those noisy electric fuel pumps behind the driver was to let you know when you're running low on fuel. Kinda like the low fuel light on the dash of your daily driver econobox.<hr></blockquote>

I can't hear my fuel pump over the sound of the exhaust. Is this a problem? How do I make my pump louder?

Actually, the gauges are not damped and do show the sloshing around. I understand it may make a difference if your sender arm is facing forward or backward. Facing backward you get less bouncing, but facing forward you have a better indication (if all is working correctly) that you are about to run out. My recent reading indicates that they may face either way.

John, BN4

 

[bob hughes]

Chaps and Chapesses, half the fun is the not knowing if you are going to make it to the next filling station or not!! I think each car is different and you soon get to know what the limits are. I use the gut feeling approach when it comes to a fill up or not, especially on a run when a good distance has already been covered. During periods of short runs you can see the stable guage-------just after you have turned the ignition on-------- and just before you press that little black button, after that, all heck lets loose.
Whilst moving, I average the swing at a steady speed to give an indication and at around ¼ full, standing or moving, I consider a top up at the next station.

 

[ThomP]

My original Fuel sender gauge was heavily damped. It would take a lot of force to get it to move, hence the sloshing in the tank did not make the needle bounce. It would eventually indicate full and correctly indicate to about 1/4 full. I thought this mechanical damping was built in to avoid the bouncing gauge syndorme that is described here. I thought that this sender had gotten too tight to work properly. I bought a Moss replacement and discovered that its free movement was shown in the gauge by the bouncing needle. I blamed this upon it being a "Cheap Chineese Copy" and started looking for an OEM part. I recently located a NOS OEM Smiths unit. It isn't damped! I'm surprised that the fuel gauges in these cars bounced like this and the fuel indicator needles survived 30+ years of bouncing.

The inside of my replacement fuel tank has no baffeling. Did the original tanks have baffels?

One other comment about the Moss unit: It broke in about two days of use. The plastic float was destroyed by the tank slosh. I was glad I kept the original unit. I took the metal float from the original and replaced the punctured plastic piece and swing arm.

Indian Head gasket shelac works well at keeping the screws from leaking.

 

[bighly]

As long as the gage is moving I know I have fuel. I was watching K19 Widowmaker last night and saw the Nuclear Officer tapping the core temperature gage. Hummm .... remided me of my Smiths fuel gage minus the meltdown.

I usually wait for level steady road or a stop light to "take a fuel level reading". I must admit if it is a bit low and I am pulling uphill I feel threatened by running out on the road. All part of the excitement I suppose.

 

[healeygal]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Bob Hughes:
Chaps and Chapesses, half the fun is the not knowing if you are going to make it to the next filling station or not!! .....Whilst moving, I average the swing at a steady speed to give an indication and at around ¼ full, standing or moving, I consider a top up at the next station.

<hr></blockquote>

Hi Bob,

I use the exact same method! It usually works pretty well, except for one day last week, when I didn't hear the fuel pump going haywire, the car sputtered, and I could feel it losing power.

Luckily, I was heading to the gas station at the time, and the car had enough momentum to roll up to the pump.

I did the same thing last year, and you think I'd learn, but as you say, it's all part of the adventure!

 

[Michael Oritt]

I recently reinstalled my fuel guage and tank sender, both of which I had sent to Nisonger's to have rebuilt and calibrated together. (BTW, I ultimately pulled and reinstalled the sender with the arm facing forward as suggested by several Healey mavens). The fuel level indicated does vary under acceleration, braking, etc. but is fairly constant at constant forces. However, I regard the fuel guage's indicator as nothing more than an interesting diversion to the road ahead and go by my tripometer, which I find to be more reliable and definitive: My gas mileage varies little whether I am driving around town or on the road--about 25 mpg at all times--I'll usually refill at 200 to 225 miles and I see no reason to plumb the depths of my fuel tank.

Best--Michael Oritt, 100 Le Mans