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BJ8 gas gauge faulty

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Hi, Dan -
Wavering fuel gauge needles are just characteristic of Healeys. I tried running another wire from the sending unit to ground and that helped but didn't stop it completely.
When on a trip I fuel up based on the odometer mileage (I can get about 240 miles on a full tank, but usually start looking for a gas station at 150 miles or so on the odometer, not so much relying on the gauge and I have never run out of gas (yet).
 
Daniel Kaminsky said:
My gauge needle flops around so never know just what fuel I have. Have run out of gas twice. Help!

Dan
'67 BJ8
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Hey!:
if it is flopping around you got gas,when it stop! ,head to the closest Petro stop N hope N pray it ain't too far away-:chuncky:
 
Hi Dan,

A number of Healey owners have severed the fuel line between the tank and pump to install a fuel filter. This line is the main ground path for the tank sending unit and, if you gauge still works at all, has caused the sending unit to find a secondary path to a ground that may not be as secure. I would attach a new ground line to the sending unit and a good frame grounding point within the boot to assure you do have a working circuit. Since the Healey's sender is not buffered, you will still have a bouncing needle.

If you want a stable reading, you will need to attach an additional circuit that averages and slows tank readings. Steve Gerow posted an added circuit a while back that. if I remember correctly, seemed quite easy to implement. However, take a look at this (https://www.minimania.com/files/SmithsVoltageStabilizer.pdf) as well.

Ray(64BJ8P1)
 
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I have a ground wire from one of the sender screws to the body. The needle still moves around, but it's stable enough on level ground at constant speed and direction to know how much I've got left. Most of the remaining flopping around is because of going uphill or down, left or right, accelerating or stopping due to the fuel moving.
 
I found the best way to see how much fuel you have is to get up to speed and then accelerate slightly but not to hard and make a visual reference on the gauge and then decelerate and make a visual reference on the gauge. Split the difference between the high and low of the gauge and you'll have an accurate reading of fuel level. It's worked for me since 1972.
 
My gauges give fairly accurate readings on level roads at steady speeds. I usually reset the trip meter at fill-up so I have at least an approximate idea if the gauge or sender go TU (200miles/tankful is all but guaranteed for the BJ8).
 
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 has had no problems.. Austin-Healey-3000-BJ8-Fuel-Tank-Sender-w-DUAL-Brushes-SALE-/361580771642
 
Not doubting you or your results, but I don't see how having dual brushes solves the problem (unless the coil and 'scraper' were defective on the old sender). I've always thought the problem was due to fuel sloshing around in the tank; hence the stable readings when the car is at rest or traveling in a straight line at constant speed. More baffles in the tank and/or a physical or mechanical damping mechanism would seem to be the cure. Most modern systems, I believe, have a combined sender and pump, and the float moves vertically and doesn't have the leverage our old-school floats have on the sender coil.
 
When I removed (over a year ago) the old fuel tank float, I disassemble it to show the "guts" to the BJ8 owner. The coil had stretched and had gaps which caused the fuel gauge reading to be inaccurate. The dual brush float is stronger and more durable. The old one will wear out, which is usually the case in all of the above threads. The BJ8 owner has had no problems with the accuracy of his fuel gauge readings.
 
Mert said:
When I removed (over a year ago) the old fuel tank float, I disassemble it to show the "guts" to the BJ8 owner. The coil had stretched and had gaps which caused the fuel gauge reading to be inaccurate. The dual brush float is stronger and more durable. The old one will wear out, which is usually the case in all of the above threads. The BJ8 owner has had no problems with the accuracy of his fuel gauge readings.
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Is the needle steady under all conditions (acceleration/deceleration, cornering, bumps, etc.); i.e. it doesn't bounce around, ever? If so, this is the solution for a chronic, er, idiosyncrasy of Healeys.
 
Bob_Spidell said:
.... Most modern systems, I believe, have a combined sender and pump, and the float moves vertically and doesn't have the leverage our old-school floats have on the sender coil.
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Most modern gauges use a bimetallic strip for the gauge which reacts slowly to changes in measurement. The Healey gauge uses a moving coil galvanometer type gauge which reacts quickly.
 
John Turney said:
Most modern gauges use a bimetallic strip for the gauge which reacts slowly to changes in measurement. The Healey gauge uses a moving coil galvanometer type gauge which reacts quickly.
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Sounds like a simpler solution to boot. Surprised the Brits didn't use it; bimetallic strips, I believe, have been used--in household thermostats, for one example--for a long time. One strange quirk my Mustang has: if I turn the key all the way to 'off' when I gas up, it behaves as expected, but if I leave it in the 'acc' position--to listen to tunes while the gas is pumping--it will register low on engine restart, and it takes a few restarts and a few miles of travel before it registers full (it gradually moves up). I can't think of a logical explanation for that behavior.
 
Mert said:
When I removed (over a year ago) the old fuel tank float, I disassemble it to show the "guts" to the BJ8 owner. The coil had stretched and had gaps which caused the fuel gauge reading to be inaccurate. The dual brush float is stronger and more durable. The old one will wear out, which is usually the case in all of the above threads. The BJ8 owner has had no problems with the accuracy of his fuel gauge readings.
Click to expand...

I don't see why the coil would "stretch" since there is no load on the wire I can think of. But after installing a replacement sending unit I got from Moss Motors several years ago, I found the gauge to be very erratic -- one moment reading full and the next reading 1/4 -- all over the place. When I opened up the sending unit I found the coil wire very unevenly wound, with several gaps along its length. That certainly would cause an erratic gauge.

The coil in the original sending unit for my car is still in perfect condition, but the wiper is almost worn in two (which is why I was looking for a replacement). Not being able to find a satisfactory replacement (other replacements from Moss had either cracks in the plastic float right out of the box, or actual holes), I'm still using the original.
 
I've been lurking here for about a month . . .

I found a couple of threads on the subject of the fuel gauge system to be helpful, especially one of which that links to the MGA guru site:

Fuel Gauge Function

I've had my BJ8 for 21 years and in all that time, I've lived with an inaccurate fuel gauge and one that has to be tapped after starting the car to get it to move off the left pin.

Calibration seems fairly simple and is explained here:

Fuel Gauge Calibration

I used a 12 VDC source and a 100 Ohm variable resistor (potentiometer) in conjunction with a digital multimeter with an accurate resistance reading capability.

Using the information provided in the link, setting the resistance between the "T" terminal and ground (earth) was as follows:

70 Ohms = full tank
52.5 Ohms = 3/4 tank
35 Ohms = 1/2 tank
17.5 Ohms = 1/4 tank
Shorting the "T" terminal to ground (0 Ohms) = E

The above presupposes the sender is functioning as intended which is true in my case . . . as I had previously replaced it!

For those of you who have a gauge that sticks, here is a very easy fix that will not be visible to anyone except those who look at the gauge under a magnifying glass.

Under a magnifier, I had noticed a very small v-notch in the gauge needle corresponding to the contact point between the needle and the stop pins below "E" and above "F." This nearly microscopic "v" acted as a friction hold on the needle itself.

Simply slip a bit of very small diameter heat-shrink tubing over each stop pin and hit it with a little heat (a hair dryer will do,) to shrink tightly over the pin. You have just rubberized the pins. Fixed!
 
Steve,

I can't say with certainty, but I doubt this type of voltage regulator would stabilize the tendency of the Austin-Healey fuel gauge to fluctuate as the float bounces around a bit in the tank with sloshing fuel.

Edit: I understand these regulators are used to stabilize the supply voltage to electronic gauges.

From a quick read on this type of device you suggest, it seems like a typical electro-mechanical relay-based regulator and i believe it may need more current flowing through the circuit than is present in the low-current system used in Healeys. From my limited Google search, the VW gauge is a thermal type which draws more current and may well allow a vibrator or relay regulator to work.

Disclaimer: I have no personal experience with these regulators. Perhaps someone with experience will respond?

Here is an article on a Smiths regulator:

Smiths Voltage Stabilizers -REVISED

Here is the pertinent part:

Vehicles with Smiths voltage stabilizers can easily be identified. If the fuel gauge needle “jumps” off the empty position when the ignition is switched on, the vehicle is NOT equipped with a voltage stabilizer. Fast responding gas gauges are based on the “balance magnet” principle and do not require the voltage stabilizer. If, however, the fuel or temperature gauges slowly drift up when the ignition is switched on, the car uses a voltage stabilizer and gauges based on bimetallic heating elements. The voltage stabilizer can be mounted any number of places. Consult your service manual to determine its location
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Our gauges are the fast-response balance magnet type and not the bimetallic heating element type.

What may work is some sort of "damper" using high-value capacitors as I have seen in another thread. In one case, someone simply added a super-capacitor (more than one Farad) across the sender.

Here's an engineer's solution from the MGA Guru, again:

Fuel Gauge Damping Circuit

The fellow explains how it works and why he added some complexity.
 
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.
 
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