gas gauge

[rjc157]

Are there any original owners out there that can say that the needle doesn't jump around has anyone solved this problem rebuilt gauge new sending unit grounded the sending unit as well as the gauge and the needle still bounces around even at idle and standing still any new ways to fix it

 

[EV2239]

The Gas gauge was all over the place from new! However, with years of experience you learn to guess accurately how much fuel there is in the tank. Usually more than it says stationary and on the level, but don't count on it. Pessimists carry a wooden rod for back up.

My car have 165/80 X 15" Vredesteins and a relatively stable speedo needle on a rebuilt instrument that reads 100mph when the car is doing 84mph.

I had an accurate electronic revcounter fitted into the original housing and read so much lower than the mechanical device, I sent it back for recalibration. The tech was sympathetic.

This is means I'm a dog slow driver with terrible gas mileage.

PS. Forty five years ago I had and E Type that claimed 160 at 120, the car's real top speed (it was an early 4.2) and a DB5 whose revcounter was so far out that we modified it in the laboratory of the company where I worked to avoid blowing the motor.

In another post I gave accurately measured BHP and torque figures for Healeys, which are very different to the wild claims people still make.

Its seems that us men don't confine exaggeration to our appendages.

 

[steveg]

Are there any original owners out there that can say that the needle doesn't jump around has anyone solved this problem rebuilt gauge new sending unit grounded the sending unit as well as the gauge and the needle still bounces around even at idle and standing still any new ways to fix it

I use the Zim's Porsche fuel gauge stabilizer:
https://www.allzim.com/store/fuel-gauge-stabilizer-356.html

At approximately $20, it reduces the swings greatly.

Also Charlie Hart & Mike Salter's method:
https://www.healey6.com/Technical/Erratic fuel gauge.pdf

Make your own dampener:
https://www.healey6.com/Technical/FUEL GAUGE DAMPENER.png

 

[rjc157]

can the Zim's product be purchased locally

 

[steveg]

can the Zim's product be purchased locally

You mean like at your friendly neighborhood Porsche 356 store? Check the bubble packs by the register.

(sorry - too good to pass up!)

 

[Keoke]

can the Zim's product be purchased locally

Well:
Since Jaguar and Daimler use stabilizers too you might check with the supporting parts houses in your area also.

 

[steveg]

Moss has an explanation of how the stabilizers work:
https://www.mossmotors.com/graphics/products/PDF/131-555.pdf

 

[shortsguy1]

I tried the second option mentioned above by Steve (the Charlie Hart and Mike Salter method), and it didn't really work for me. In my case, the fluctuating gas gauge must not have been due to a grounding issue of the float arm. I like the capacitor solution. I hadn't read about that until just now. Thanks for posting it Steve.

 

[Keoke]

I like the capacitor solution. I hadn't read about that until just now. Thanks for posting it Steve.

Well that capacitor solution will be about as effective as the Ground strap one OK

 

[andrea]

https://mgaguru.com/mgtech/electric/fg_06.htm
https://mgaguru.com/mgtech/electric/fg104.htm
(same Fuel gauge of AH )
This is a complete rebuild articles to know- for your Fuel Gauge understanding, test and repair -- also extended to sender unit problems

 

[steveg]

I like the capacitor solution. I hadn't read about that until just now. Thanks for posting it Steve.

Well that capacitor solution will be about as effective as the Ground strap one OK

Have you actually tried either of these solutions, Keoke?

I've found the capacitor solution reduces the jumping-around of the gauge as the tank sloshes by a noticeable amount. Have used the jumper wire. It's not perfect, but is inexpensive and easy to implement.

 

[Keoke]

Have you actually tried either of these solutions, Keoke?

I've found the capacitor solution reduces the jumping-around of the gauge as the tank sloshes by a noticeable amount. Have used the jumper wire. It's not perfect, but is inexpensive and easy to implement.

Yes, Steve:
However, as you say they are not "perfect' solutions.

I found if you want to STOP the fluctuation use a voltage stabilizer for that gauge or just keep the tank full.

Related to this circuit but not a cure for its jumping around is:

Add a good ground wire from the sensor body to the car chassis close by in the boot.

OH! That Mossy thing may work too ,but I do not know

 

[Goldie]

My BJ8 gauge and sending unit were original until I restored my car. One of the problems with the needle jumping during driving is the way in which current passes through the meter movement. It works on the principle of how much current is passing through the resistance in the sending unit at the tank relative to a reference resistance coil. There is a wiper on one side of the wire wound resistor in the tank. That tends to get a little loose and does not make great contact with the resistance wire. Newer versions use wipers on both sides of the resistor wiring. You will always get some needle movement even with those.

 

[steveg]

My BJ8 gauge and sending unit were original until I restored my car. One of the problems with the needle jumping during driving is the way in which current passes through the meter movement. It works on the principle of how much current is passing through the resistance in the sending unit at the tank relative to a reference resistance coil. There is a wiper on one side of the wire wound resistor in the tank. That tends to get a little loose and does not make great contact with the resistance wire. Newer versions use wipers on both sides of the resistor wiring. You will always get some needle movement even with those.

Original senders have the wipers on both sides.

 

[steveg]

Keoke -
The Moss stabilizers are replacements for '70s MG gauges which work on a bi-metallic heat-related principle - different from ours. I attempted to fit their stabilizer to the Healey gauge without success. The only stabilizer which will work on a stock Healey "moving-metal" setup is the capacitor-type such as Zim's or Hardie's.

 

[RAC68]

Hi Ralph,

The gas gauge has always bounced and increased its active jumping as the fuel gets lower in the tank.

I still have my original float and many have increased the bounce by NOT installing the sending unit with the float toward the front of the tank. Originally, the ground for the sending unit is provided by fuel pump mounting and as connected through the metal fuel line going from the tank to the pump. When some have installed a fuel filter between the tank and pump, the original ground is usually lost. If the gauge still works, it is because a less secure ground was found through another connection someplace or a replacement ground was connected to one of the sending unit housing nuts. In either case, a ground, weak or strong, was present for the gauge to work.

One last point. The SU fuel pump uses a coil in its operation and, although it is a 12V unit, the effect of the coil induces voltage to as much as 10 times that amount. With the installation of a TSV diode that grounds anything ove4 23 Volts to ground, I have found the gas gauge to be a little less jumpy (not as stable as in a modern gauge). Although I can't say that the reduction in induced voltage within the fuel pump has any affect on fuel gauge reaction, it is possible and my points longevity and pump reliability is a result of this addition.

Although you can add a circuit that will stabilize your fuel reading bounce by slowing and short-time averaging response, I have found that the original was not that bad and, other then the needle needing a tap when the car first started, I feel the gauge bounce is another reflection of the raw temperament of the car that I like.

All the best,
Ray(64BJ8P1)

 

[Keoke]

Originally, the ground for the sending unit is provided by fuel pump mounting and as connected through the metal fuel line going from the tank to the pump.

Yep Ray:
However, that certainly is not a dedicated ground and has caused problems over the course of time.

 

[RAC68]

Yes Keoke,

That is why I mentioned the effect of the SU pump coil on the level of voltage passing through the points. This is why I think there is a possibility that the TVS diode implementation may have also assisted as it brings down the voltage build-up from around 200 Volts to a limit of 23 Volts (the TVS I chose).

Ray(64BJ8P1)

 

[Keoke]

Yes Keoke,

That is why I mentioned the effect of the SU pump coil on the level of voltage passing through the points. This is why I think there is a possibility that the TSV diode implementation may have also assisted as it brings down the voltage build-up from around 200 Volts to a limit of 23 Volts (the TSV I chose)
Ray(64BJ8P1)

Yep
Improved points longevity and pump reliability is the result of replacing the original capacitor arc suppressor with the TSV diode.
The capacitor over time would dry out and fail or simply break down.
However,today an electronic SU pump solves all the problems of yesterday.-

 

[RAC68]

Do you remember the electronic SU failures not too long ago? Yes, in most cases an electronic replacement is a more reliable replacement to a mechanical or electric device. However, in this case, the 5 cent TSV addition has more then been worth the cost and effort with added longevity. Yes, my pump is old but it also is working and has been beating for a number of years without hesitation or further maintenance.

Ray (64BJ8P1)