Ran out of gas the other day whilst at idle queueing up for the tip. It just stopped (normally if you are driving you start loosing power, but as I was stationary that didn't happen), which at the time didn't strike me as odd as I thought the tank should have been almost empty after the last time I used it.
...Or so I thought.
Filled up and found there was still at least 12 litres left in the tank. Upon trying to start on LPG it would catch and then immediately die, and if I tried to change from petrol to LPG whilst going along the motorway with foot flat to the floor (i.e. highest demand situation for the vapourizer) it wouldn't play at all.
A bit of investigation was in order; a quick check established gas was getting to the vapourizer and the initial 3 second "prime" when the key was turned was working as it should (which explains why it would catch initially then die as I'd got some gas into the manifolding). So it was time to investigate further.
One seriously mucky vapourizer as wrestled off the vehicle:
Liquid propane (high pressure) enters through the hex fitting just above the two chambers. The big round plastic outlet at top centre is the low pressure gas to the mixer, the other two plastic fittings are the inlet / outlet for the water circulation, the solenoid is to cut the gas flow to the low pressure side.
Unscrew the peripheral ring of 6 screws, turn it over and wrestle the back off:
The diaphragm is still connected to the internal gubbins of the vap. The inside of that when in use will be in an LPG environment, the side visible is open to the atmosphere (necessary for the demand system to work). A couple of things are apparent:
1) The visible side of the diaphragm is filthy dirty, and
2) The muck and water has been coming in from the vent hole on the rear face and collecting in there (see the rust stain at the bottom?). My vapourizer is positioned where the washer bottle used to be, and as a result when in mucky conditions or splashing about some of the crap that manages to get in between the bonnet and the wing ends up in here. I will have to bodge up a shield or something.
Remove the diaphragm:
To reveal a mucky mess. Autogas is not always the clean fuel you'd be led to believe! The lever gubbins are to preload the pressure on the main diaphragm (which in turn will control how quickly it can respond to the engine's demand for fuel) - controlled by the larger of the two nuts visible on the right - and the "idle bypass", controlled by the smaller.
As you can imagine the inside of the diaphragm is coated in this mucky stuff, and it seems to be incredibly flaccid:
Flip it back over and remove one of the high pressure chamber covers:
There's some goop in there too. It came off with a bit of a pop, so I assume there was some trapped pressure in there. That smaller diaphragm controls the gas flow from the high pressure chamber to the low pressure chamber at the back (but the HP chamber is actually underneath that diaphragm).
Remove the other cover:
There's a diaphragm (not shown) and a big spring (bottom right) on top of this chamber connected to that rod which rocks and opens and closes the HP valve to allow liquid gas to enter; you can see part of that valve unscrewed just to the right (see the green o-ring seal). This chamber is where the liquid initially vapourizes, and as you can see there's still a fair amount of muck in there.
Remove the HP chamber assembly and turn over:
Quite simple really; it's an empty chamber filled with water! The pipe snaking through it is the HP feed from the initial inlet to the valve on the side of the vap.
And finally:
The "bottom" - as it were - of the water chamber. The two brass fittings carry the gas through from the HP to the LP side. The smaller of the two is for a small amount of gas that always flows, called the "idle bypass", which ensures your engine doesn't stop when the throttle is closed and the demand from the engine drops massively (such as under heavy braking).
Looks like I've got a rebuild kit to order and some pretty intensive cleaning to do!
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