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Topic ClosedGas tank gauge

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Vanorak
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Direct Link To This Post Topic: Gas tank gauge
    Posted: 24 Jun 07 at 20:01
Did anyone get to the bottom of the faulty gas tank gauge problem? How do they work? Can they be repaired without blowing yourself up? Are new units available?
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Yardie
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Direct Link To This Post Posted: 01 Jul 07 at 00:38

I'm also still waiting.

Apart from one user who was convinced they work on pressure! I had no other comments.

I know the gauge it'self is magnetic and is simply screwed to a holder against the tank, I'm guessing that there must be some sort of mechanical linkage and float with suspended magnet INTERNALLY.

ANYONE HAVE ANY DEFINATE INFO ON HOW THESE WORK?

Martin

On wings like angels whispers sweet

my heart it feels a broken beat

Touched soul and hurt lay wounded deep

Brown eyes are lost afar now sleep xxHayleyxx



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Direct Link To This Post Posted: 02 Jul 07 at 19:44
They work on a float system. Inside the tank there's a float made out of thin metal. The float is mounted on an arm that runs length-ways down the tank and (from memory) is about 20cm long. This arm pivots around a mechanism that goes into the tank from the plate on which the gauge is mounted. Running down from the mounting plate to the pivot point inside the mechanism is a shaft that can rotate. At the pivot point there are 2 gears that turn the pivoting motion of the float into a rotating motion on the shaft. At the mounting plate end of the rotational shaft there is a magnet attached to the shaft which rotates with the shaft.

The reason this arrangement is used is because of the high pressures inside the LPG tank. If you tried having any direct interface between the LPG and a normal gauge, chances are you'd just blow the gauge out unless it was a gauge rated to a very high pressure and thus costing a ton. This arrangement means a normal cheapo gauge can be used as there is no direct interface between the LPG and the gauge.

Now, before i get on how to repair them, a word of warning. I've already fixed my gauge using the method described below but if you attempt the same, you do so at you're own risk. As i'm sure you already know, LPG is very explosive stuff so before you even consider working on it disconnect all electrical equipment in the vicinity, including both batteries. Make sure the LPG tank is empty, fridge is off, there are no naked flames to be seen for miles and make sure your mobile phone is switched off. If you are in any doubt then get someone qualified to do it for you.

If you're sure the tank is empty, then the mounting plate can be removed by undoing the 4 allen bolts. When they're undone the mechanism can be withdrawn carefully through the hole. At first it looks like it won't fit but with a little gentle jiggling it can be removed. The important thing is not to force it as it's quite delicate. When it's out the chances are that it will have seized. Use plenty of WD40 and you should be able to free it up. Place the dial back on and the needle should change position depending on the position of the float. When everything is running smoothly again it can be returned to the tank. I used a very small amount of instant gasket around the sealing edges of the mounting plate to ensure it sealed.

After that you can half fill the tank and then check around the mounting plate for leaks using soapy water. For the next few days i'd check a once a day with soapy water to make sure that it's still pressure tight.

Once again, LPG is not to be messed with so please don't attempt anything you're not comfortable with.

Dave

PS : Call me paranoid but i always drain the LPG tank before doing any welding on my van. I know i've petrol in there as well but the petrol tank on my syncro is plastic. As the LPG is metal i'd be worried about any sort of arcing taking place between the LPG tank and any sort of ground if your ground wire comes off or isn't good.
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Vanorak
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Direct Link To This Post Posted: 02 Jul 07 at 20:54
Cheers for that info Dave, how do you go about emptying the tank though? Run the gas hobs for a week? Not sure if my tank is full or empty. Gauge seems to be a bit haphazard, sometimes it`s showing around 70%, some days it`s at 90% (I wondered if it was the warm weather (the other week!) that was doing it, making the gas expand and show more on the gauge?
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Scruff Daddy

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Direct Link To This Post Posted: 02 Jul 07 at 21:30

remind me to put this in "useful threads" will you!

I tend to use "active topics" at the top of the page and forget about useful stuff like this.

If I put it in useful threads it gets locked automatically, and I don't want to lock it yet.

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Vanorak
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Direct Link To This Post Posted: 02 Jul 07 at 21:38
Did you see Irish Daves info with fots on upgrading the Westy onboard charger to a modern 3 stage Si? Was on 80-90, maybe on here. Well worth adding to info, did mine just as he had done, great job.
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Scruff Daddy

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Direct Link To This Post Posted: 02 Jul 07 at 22:16
Link?
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Vanorak
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Direct Link To This Post Posted: 02 Jul 07 at 22:53
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Yardie
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Direct Link To This Post Posted: 02 Jul 07 at 23:44

Irish.dave nice one! and a useful thread for others.

It's reinforced what I suspected, but it's nice to have someones own experiences to go on before taking the plunge and stripping it myself.

I know it;s not a big deal but things like this really bug me so it's just gotta be done sometime soon.

Martin

 

On wings like angels whispers sweet

my heart it feels a broken beat

Touched soul and hurt lay wounded deep

Brown eyes are lost afar now sleep xxHayleyxx



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Direct Link To This Post Posted: 22 Jul 07 at 21:42

I've just fixed mine so I thought I would just add my findings:

The mechanisn wasn't seized, it was a leaky alluminium float, infact I suspect this is the more common reason for faulty operation.

The float screws onto a rod and it is this threaded hole that allows LPG to leak into the float, mine was actually loose on the thread.

I used proper "GAS PTFE" tape on the threaded bar to reseal the hole in the float, then  I tested it by plunging the float completely in hot water, checking for bubbles escaping from around the thread.

I was pretty impressed with this clever bit of "German enineering" but quite amazed that they would put a threaded hole in a float, especially when you consider it has to live is a pressurized container full of liquid. Floats in carburrettors for instance, are fully sealed and have the pivot brazed or tin soldered to the body, not a hole in sight! a very poor oversight me thinks! 

Martin

On wings like angels whispers sweet

my heart it feels a broken beat

Touched soul and hurt lay wounded deep

Brown eyes are lost afar now sleep xxHayleyxx



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