BJ8 gas gauge faulty

[dklawson]

I would like to add a footnote or two to the posts above.

Do not install a voltage stabilizer to the earlier gauge systems with the magnetic gauges... at least don't add a Smiths electro-mechanical stabilizer. The Smiths stabilizers switch their output on and off rapidly. If you connect one to an early magnetic gauge it is effectively turning the gauge on and off rapidly. Instead of making the gauge appear damped, it can make the needle flutter or bounce more.

You could install one of the modern solid state stabilizers to the system such as those sold by Moss. However, the bouncing you observe with most magnetic gauge installations are not due to fluctuations in the car's charging system but vibrations, sudden body movements, and in the case of fuel gauges, sloshing inside the tank.

 

[Joe A]

The mgaguru site is full of interesting and helpful information. For the fuel gauge calibration procedure, be aware that it is based on the Jaeger gauge used in the MGA. A Smiths gauge is used in the Austin-Healey and it needs different values. The resistance seen by the gauge when the tank is full is 90 - 100 ohms, not the 68 ohms for the Jaeger gauge.

Steve,

Thanks.

So if the gauge should read full at 90 Ohms, then to check calibration and linearity, it would seem that:

- 0 - Ohms = E
22.5 Ohms = 1/4
45 Ohms = 1/2
67.5 Ohms = 3/4
90 Ohms = Full

I'm showing Full tank now when I fill up and look down the filler tube and confirm full, but I'll do some additional investigation as well at some point.

Bob . . .

Improving the ground can't hurt.

Edit: The calibration procedure is rather simple and for the first 21 years I have owned the car, my gauge showed about 7/8 when full and about a little less than 1/2 when empty, so non-linear for all these years. Now it seems to be working +/-

But driving on lonely roads, it would still make sense to fill up any time there is any doubt.

 

[steveg]

I would like to add a footnote or two to the posts above.

Do not install a voltage stabilizer to the earlier gauge systems with the magnetic gauges... at least don't add a Smiths electro-mechanical stabilizer. The Smiths stabilizers switch their output on and off rapidly. If you connect one to an early magnetic gauge it is effectively turning the gauge on and off rapidly. Instead of making the gauge appear damped, it can make the needle flutter or bounce more.

You could install one of the modern solid state stabilizers to the system such as those sold by Moss. However, the bouncing you observe with most magnetic gauge installations are not due to fluctuations in the car's charging system but vibrations, sudden body movements, and in the case of fuel gauges, sloshing inside the tank.

I tried one of the Moss stabilizers on my fuel gauge. It requires a matching gauge with similar heating element. The later gauges and stabilizers go together.

PS - I've been pushing the Porsche capacitor, but like the guy in the MG article says, it doesn't work that well. Plus it seems to reduce the range of the gauge, so when I fill up just under the cap, it shows 3/4 tank.

 

[John Turney]

My gauge is fairly accurate between full and 1/8 of a tank, but it still moves around due to fuel slosh. With a magnetic gauge, you won't be able to stop that. If you replace the magnetic internals with a bimetallic internals it will dampen the sloshing effects.

 

[dklawson]

If you replace the magnetic internals with a bimetallic internals it will dampen the sloshing effects.

You cannot transplant the inards of a magnetic gauge to a bimetallic gauge or the other way around.

The later bimetallic gauges work by resistance heating. The higher the resistance of the sending unit, the lower the gauge reading. The early gauges work exactly the opposite. The higher the sending unit resistance the higher the reading. (Opposite direction of change and a different resistance range).

You can switch the senders and gauges together as pairs... adding the stabilizer if needed. OR, you can order a product like the Gauge Wizard by Spiyda Design that will allow you to mix and match senders and gauges. The Spiyda board should also let you tweak the calibration at the same time.

Link to Spiyda Gauge Wizard

 

[steveg]

You cannot transplant the inards of a magnetic gauge to a bimetallic gauge or the other way around.

The later bimetallic gauges work by resistance heating. The higher the resistance of the sending unit, the lower the gauge reading. The early gauges work exactly the opposite. The higher the sending unit resistance the higher the reading. (Opposite direction of change and a different resistance range).

You can switch the senders and gauges together as pairs... adding the stabilizer if needed. OR, you can order a product like the Gauge Wizard by Spiyda Design that will allow you to mix and match senders and gauges. The Spiyda board should also let you tweak the calibration at the same time.

Link to Spiyda Gauge Wizard

Looks promising - did you buy one?

 

[dklawson]

No. I have not bought one. However, the man who runs the business is a Mini owner and I have corresponded with him. He knows his stuff.

 

[jpat67bj8]

Go to eBay. Look for a double coil fuel tank float. A buddy of mine had the same problem his BJ8. I got the tank float, installed it and he have had no problems.. Austin-Healey-3000-BJ8-Fuel-Tank-Sender-w-DUAL-Brushes-SALE-/361580771642

ordered this double brush unit from Ebay. i have installed. I don"t know how it works, but so far I finally have a gas gauge that works. If you are a non-believer, all I can say as just try it. I have no interest in the company. Just wish I did.

 

[Bob_Spidell]

ordered this double brush unit from Ebay. i have installed. I don"t know how it works, but so far I finally have a gas gauge that works. If you are a non-believer, all I can say as just try it. I have no interest in the company. Just wish I did.

Website for this item states "... product has been reconfigured to incorporate dual brushes (internal contact arms) just as the OEM Smiths units had ..." This doesn't say, to me, that this replacement is superior to OEM, so wouldn't necessarily cure the 'jumpy needle' problem. Does 'have a gas gauge that works' mean it works comparable to OEM, or is there some improvement?

If $50 cures this problem, I'm in.

 

[jpat67bj8]

Sorry, I was not clear in my above statement. As I had tried about every recommendation listed in previous blogs including a complete replacement of both gauge and sending unit with no difference in the floppy needle< I bought the double brush unit from Ebay. I installed the unit today and drove the car for a fill up. I checked the amount of gas in the tank while gauge out with stick and guessed that I had maybe 3-4 gals of gas. I filled with 11 gals. I did notice that gauge read close to empty on way to station and no flickering of the needle. After fill up, the gauge read full. I only drove the car about 10 miles on hilly curvey roads and no flickering and still read full when I returned home. at this time I am excited that the problem appears to be solved. Time will tell if this remains true. I always drove by mileage traveled and probably continue until I am 100% sure that this really works. To me this, at this time, is $50 well spent. I will add that when I met my wife many years ago, she had a new 1964 Healey. Neither of us remember any problems with fill gauge.

 

[Bob_Spidell]

Cool. Thanks for the feedback.

re: "... I will add that when I met my wife many years ago, she had a new 1964 Healey. Neither of us remember any problems with fill gauge." No chance you had other things on your minds at the time?

 

[steveg]

Sorry, I was not clear in my above statement. As I had tried about every recommendation listed in previous blogs including a complete replacement of both gauge and sending unit with no difference in the floppy needle< I bought the double brush unit from Ebay. I installed the unit today and drove the car for a fill up. I checked the amount of gas in the tank while gauge out with stick and guessed that I had maybe 3-4 gals of gas. I filled with 11 gals. I did notice that gauge read close to empty on way to station and no flickering of the needle. After fill up, the gauge read full. I only drove the car about 10 miles on hilly curvey roads and no flickering and still read full when I returned home. at this time I am excited that the problem appears to be solved. Time will tell if this remains true. I always drove by mileage traveled and probably continue until I am 100% sure that this really works. To me this, at this time, is $50 well spent. I will add that when I met my wife many years ago, she had a new 1964 Healey. Neither of us remember any problems with fill gauge.

Please send a followup after you've run it for a few months to see if it still works per above.

 

[Bob_Spidell]

I just ordered one for my BJ8. Supposed to come Tuesday, but might take me a week to get it installed.