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fuel sending unit float position

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AUSMHLY

AUSMHLY

Yoda
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We all know that the fuel needle travels all over the place while we drive. To be sure how much fuel we have, we need to have the Healey stopped on level ground to get an accurate reading on the fuel gauge.

Does having the float on the sending unit facing towards the front of the car or backwards make any difference in how accurately it reads the level of fuel in the tank?

It seems to drop in, fit both ways. I just don't know what's happening when it's in the tank, being there are baffles and the shape of the tank. Is travel non restricted both ways?

The sending unit has a cork seal under the rectangular top, I assume that fuel gets in the unit. True?
 
The float needs to be pointed forward. That way, it rotates down into the recess where the fuel pickup is located before it comes to a stop. This is below the floor of the tank proper. If the float points backward, it will come to rest on the bottom of the tank while there will still be some rotation left.

I've determined this by observation with a spare tank.
 
Roger,
Is that float foam??
If it is I would send it right back where it came from there
is a source for one with a brass tank I no longer have the data though .Maybe some of the other listers do. OH yes the float faces the front of the car.--Fwiw--Keoke
 
Keoke said:
Roger,
Is that float foam??
Click to expand...

:thankyousign: Steve. Great explanation.
:savewave: Keoke, it's some type of hard plastic.
This unit if available from Ebay, NOS locators in RI, click here
It seems like a good design, with dual brushes like the Lucas original had.
 
ausmhly, the plastic ones were not around when i changed any of mine, just a reminder--dont over tighted the fasteners, it will distroy the new seal. :yesnod:
 
I ordered the one from NOS locators and have it on my bench right now. My Lucas one stopped working. Yesterday I opened it up to find the thin wire that runs along the top broke. I soldered it and now it works again.
 
I've been comparing the Lucas to the reproduction and find with the reproduction model the fuel gauge does not flicker as much.

I googled about the flickering and found someone who attached a copper wicking wire onto the body and shaft of the sending unit. To make sure the shaft was not contributing to the grounding situation.

OK, I can try that. Here's what I did.
It may slow down the bobbing of the float, which may help the gauge needle from flickering....as much.
If it does not work, I can remove it.
Any thoughts on this?
 
Here's what I did.
It may slow down the bobbing of the float, which may help the gauge needle from flickering....as much.
If it does not work, I can remove it.
Any thoughts on this?

Yep: it will work if and only if all the screws in the assembly are somehow electrically isolated from the case.
However, this will not improve the dampening of the gauge.To accomplish that will require the installation of a Voltage stabilizer like used in most other LBC.--Fwiw--Keoke
 
Your "flickering" may have been caused by the wire about to disintegrate. It is nice to see a part of your car that is not polished (yet). Your choice of braided wire should flex enough that it shouldn't effect the float movement.
 
The flickering is due to the gauge being able to almost instantaneously represent the float position when the fuel is sloshing about. Violent flicking from full to empty is due to a worn out sender winding and going open-circuit briefly at certain positions.

Fitting a voltage stabiliser may cause the gauge to malfunction. The voltage stabiliser is for later bi-metallic (slow moving) gauges which rely on a heater coil bending a bi-metallic strip. These are quite sensitive to changes in battery voltage hence the regulator.

Electrically it may/should be possible to damp the gauge by placing a capacitor in parallel across the tank sender. This will filter out rapid changes of the voltage in the gauge wire and hence slow the response. Depending on the size of the capacitor required (trial and error) a small resistor may be needed to limit inrush current at key-on.

I rather like the flickering gauge... when it stops flickering completely I know I'll be taking a break from driving in less than one minute.
 
Are you talking about fluctuation or a flicker? The gauge fluctuating would be due to the "tides" in the tank. Roger, can you switch out the floats.
TH
 
160514383446 Roger go here on E Bay and look--Keoke
 
I've always made it a practice to run a ground wire from under one of the mounting screws to a chassis ground. It seems to stop a lot of the flickering. Apparently the gas tank is isolated from the chassis.
 
. Apparently the gas tank is isolated from the chassis.

Well lets hope not but with all these Facet pump installations or similar breech's of the fuel lines continuity it certainly can be.

The original method ,which I am not championing, for grounding the fuel tank was via its fuel line.

.Adding a ground such as you defined is a prudent addition to the grounding and safety of the fuel tank as well as improving the operation of the fuel gauge.--Fwiw--Keoke
 
Keoke said:
160514383446 Roger go here on E Bay and look--Keoke
Click to expand...
:savewave: Thanks Keoke for finding that.
I think it's the correct unit, even though he writes in the description, not including the BJ8:

Correct fitment to the Austin Healey 100/4, 100/6 and 3000 sportscars, not including the BJ8.
 
57_BN4 said:
The flickering is due to the gauge being able to almost instantaneously represent the float position when the fuel is sloshing about. Violent flicking from full to empty is due to a worn out sender winding and going open-circuit briefly at certain positions.

I rather like the flickering gauge... when it stops flickering completely I know I'll be taking a break from driving in less than one minute.
Click to expand...

There's a rebuilt Smith unit on Ebay right now. How would I know if it works a good as a NOS unit. The sender winding spool would have to have been replaced, correct?

How can I tell if my Smith sender winding is worn? The two brushes make a solid connection the entire length of the spool. Are the winding coated with something and that coating has been rubbed off in some areas?

Would the larger amount of flickering the smith's unit has over the reproduction unit, have anything to do with my soldering the broken wire at at the back of the unit. If you look at that area in the photo, you can see the repair. Broken wire, no work. Soldered wire back together, she work. Could that solder have anything to do with it?

The Smith's float is heavier than the plastic reproduction float. I would have thought the lighter plastic float would move more and cause more movement with the fuel gauge needle. But not the case. Whatsupwidthat?

As far as visual flicking stopping letting you know you're out of petrol, you may even hear the fuel pump clicking really fast. It's morse code for, pull over immediately!
 
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