Propane tank gauge

K

Ken B

Well-known member
Oct 9, 2002
16,833
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Well my Propane tank gauge has been staying slightly above empty for at least a year. I know there is some fuel still in there. I used both the
refrigerator and the furnace at the Shawnee rally the gauge never moved after two weeks. I haven't filled the tank for about two years so it should
be somewhere around 1/2 full or slightly less.

Today I decided to find the problem. I removed the wire from the sending unit on the tank and the gauge in the coach went to full scale one way. I
then jumpered the sending unit wire to ground and it went full the opposite direction. So the wiring and the inside the coach gauge are working. (I
forget which way is full and which is empty).

I removed the sender and cleaned the mounting (ground side) and also the terminal where the wire goes. I put an ohm meter across the sending unit and
with a magnet across the back I moved the gauge from empty to full and back again. I got the expected readings between 0 and 90 ohms. So the
sending using unit also looks good.

Not knowing exactly how much fuel is in the tank I set the gauge to 1/2 and remounted it. Now that it is mounted it still reads 1/2. If I remove it
and set it to 3/4, then it stays at 3/4 when remounted.

So here is my question. How do I get the sender to re-sync with the float (and magnet) inside the tank?

I plan to go for a ride and bounce the liquid around inside the tank to see if that helps re-sync the float to the sending unit again.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Ken,
I had the same issue when I took my sensor off. When I re-installed it, I fiqured the magnet in the tank would pull it to the current setting, but
no.. So I used a magnet to set the sensor approximately where I thought the level was, then I rotated the sensor back and forth in its holder until
the gauge locked to the internal tank magnet.

My gauge still does not work because my sensor is intermittent, but the visual pointer does work. I've since taken the OEM tank out and I am using a
20lb bbq style tank.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
> Well my Propane tank gauge has been staying slightly above empty for at least a year. I know there is some fuel still in there. I used both the
> refrigerator and the furnace at the Shawnee rally the gauge never moved after two weeks. I haven't filled the tank for about two years so it should
> be somewhere around 1/2 full or slightly less.
>
> Today I decided to find the problem. I removed the wire from the sending unit on the tank and the gauge in the coach went to full scale one way.
> I then jumpered the sending unit wire to ground and it went full the opposite direction. So the wiring and the inside the coach gauge are
> working. (I forget which way is full and which is empty).
>
> I removed the sender and cleaned the mounting (ground side) and also the terminal where the wire goes. I put an ohm meter across the sending unit
> and with a magnet across the back I moved the gauge from empty to full and back again. I got the expected readings between 0 and 90 ohms. So the
> sending using unit also looks good.
>
> Not knowing exactly how much fuel is in the tank I set the gauge to 1/2 and remounted it. Now that it is mounted it still reads 1/2. If I
> remove it and set it to 3/4, then it stays at 3/4 when remounted.
>
> So here is my question. How do I get the sender to re-sync with the float (and magnet) inside the tank?
>
> I plan to go for a ride and bounce the liquid around inside the tank to see if that helps re-sync the float to the sending unit again.
Ken,

For the first 15 years or so that I have owned my GMC, my LP gas gauge never worked consistently. Occasionally it would work, but most of the time it
did not. I checked the wiring like you did and found that to be OK. I even replaced the sending unit with a new one and still no consistent
readings. As a result, I assumed that the problem lay in the float mechanism in the tank and planned to have that replaced at some time in the
future.

A few years ago I decided to take a closer look at the sender and how it fits on the tank. I noticed that it did not seat all the way to the bottom
of the socket it sits in by about 1/16". Since I had a spare sender, I decided to grind down the circumference of my spare sender enough so that it
would seat all the way in the socket to see if that might make a difference. I did that, and guess what, the ground down gage started to work!

The problem all along was that there was too much space between the sender and the magnetic coupling part of the float.

Your tank and gage might be different, but since we both have Palm Beaches of approximately the same vintage you might want to check your sender's
fit.
--
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com


Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator, Manny Tranny etc.
 
Thanks Bruce and Richard.

Richard, After reading your suggestion on clearance on the rear of the sender, I got another idea. How about I take some clay and put it behind the
sensor to determine exactly how much gap is there. Then remove the clay and fashion a steel shim much like a washer and fill that gap. Now the
magnetic flux lines travel through steel which is a much better conductor than air. I already polished the back of the sender and the place where it
goes on the tank with scotch brite and a dremmel tool wire brush. So those surfaces are clean and shiny.

Thanks again for the ideas. I do not want to cut down and possibly destroy the existing sensor as a new one is $60.00. Now if I had an old tank to
take one off of that would be a different story.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> Thanks Bruce and Richard.
>
> Richard, After reading your suggestion on clearance on the rear of the sender, I got another idea. How about I take some clay and put it behind
> the sensor to determine exactly how much gap is there. Then remove the clay and fashion a steel shim much like a washer and fill that gap. Now the
> magnetic flux lines travel through steel which is a much better conductor than air.
>

Ken,
There might be a problem.
That iron washer could be an effective Faraday Shield to keep the magnetic flux from the sender....
Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
> Thanks Bruce and Richard.
>
> Richard, After reading your suggestion on clearance on the rear of the sender, I got another idea. How about I take some clay and put it behind
> the sensor to determine exactly how much gap is there. Then remove the clay and fashion a steel shim much like a washer and fill that gap. Now the
> magnetic flux lines travel through steel which is a much better conductor than air. I already polished the back of the sender and the place where
> it goes on the tank with scotch brite and a dremmel tool wire brush. So those surfaces are clean and shiny.
>
> Thanks again for the ideas. I do not want to cut down and possibly destroy the existing sensor as a new one is $60.00. Now if I had an old tank
> to take one off of that would be a different story.

That makes sense. I only ground the one I had because I had a spare.
--
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com


Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator, Manny Tranny etc.
 
Matt:

My thought was give I a try. Transformer cores are steel. Then I thought of stainless fender washers, but I think that would be even worse. Since
they are non-magnetic. It does not take a very strong field to move the gauge/ sender. I was doing it yesterday with the magnetic clip on a pocket
flashlight.

It is something I'll probably play with sometime. I would really like to know how much propane I have in it without removing the whole tank and
weighing it or taking it in and filling it up again. I honestly do not remember when (what year) I filled it up last. .
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
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