Impco model-L LPG converter teardown

[dom14]

Hi Guys,
I finally dismantled the old LPG converter with the hope of rebuilding it with a kit.

http://www.ebay.com.au/itm/GENUINE-IMPCO-MAJOR-MODEL-L-REPAIR-OVERHAUL-KIT-INSTUCTIONS-/262022243067?hash=item3d01be22fb

I removed it 'cos the converter stopped working.

However, when I opened up, I couldn't find any excess build up of gunk, any torn or cracked diaphragms, any cracks on the body or badly damaged gasket edges. No loose bolts or nuts either.

I'm wondering whether spending money on a kit is worth it for this unit($85 for the rebuild kit)

Not sure the reason for the converter to stop working. It wasn't leaking any gas from gaskets, but just stopped working.
Now I'm not even sure whether it actually stopped working or whether it was something else(like the faulty filter or lock-off valve).
I replaced with a secondhand unit, which seems to be running ok atm.

I can clean the diaphragms with detergent water and the body with degreaser and put it back together with a bit of good gasket sealant.

Should I rebuild it with a kit? Or should I just clean it and put it back together?
What was the possible reason for it to stop working?!

Any help will be appreciated.

[threedogs]

carbi cleaner works a treat on them.
if it all looks ok save the kit for later on or get your monies back
The rubber doesn't tear it enlarges and goes floppy

[dom14]

carbi cleaner works a treat on them.
if it all looks ok save the kit for later on or get your monies back
The rubber doesn't tear it enlarges and goes floppy

Thanx mate. Which rubber part did you mean? Is that diaphragm on the last picture(black one)?

[NissanGQ4.2]

Did you have a backfire prior to it stop working?

Is it duel fuel, If so did it start / run on petrol?

[dom14]

Did you have a backfire prior to it stop working?

Is it duel fuel, If so did it start / run on petrol?

yes, it's dual fuel. It was ok with petrol, if I recall it correctly.
It was having trouble with LPG and it was making a grumbling noise(it still does even with the replacement one, which I think is from the lock off valve or filter)
When it failed to start or cut off during driving on LPG, I switched to petrol and usually it went ok.
One day, it didn't start on LPG at all. So, I got a replacement secondhand one.
I don't think I had noticeable backfire during that time.

As soon as I replaced the converter, things went back to normal.
But, now I'm not too sure. I'm wondering whether it was a coincidence and the real problem was in the lock off valve & filter.
The reason is that I was expecting the converter to be in pretty bad shape when I opened it up yesterday.
But, it looks pretty good inside. I'm sure it can do with a clean, but there was no leaks of LPG from the converter gasket edges(or water leaks).

I'm just wondering whether I accidentally cleaned a blockage when I opened up the LPG plumbing to replace the converter.

I'm guessing, it might be a good idea to give the converter a good clean and the diaphragms a good clean then put it back together with some gasket sealant and then fit it in and see how it goes??!!

The rebuild kit is dearer than a used replacement converter. I would rather save the $85 I spend on the rebuild kit if it doesn't need a rebuild kit.

[NissanGQ4.2]

Don't know if it will help but replace the diaphragm in the second pic ( I guess u could gasket seal it when putting back on ). I notice it has a tear around the bolt hole, from my understanding from the guy that fixed my crappadore when it had gas issues, Even the slightest air leak there will cause issues.

I even keep a spare one now just in case it backfires and tears the diaphram, although when I had a major backfire and it tore it wouldn't start on petrol either

[dom14]

Don't know if it will help but replace the diaphragm in the second pic ( I guess u could gasket seal it when putting back on ). I notice it has a tear around the bolt hole, from my understanding from the guy that fixed my crappadore when it had gas issues, Even the slightest air leak there will cause issues.

I even keep a spare one now just in case it backfires and tears the diaphram, although when I had a major backfire and it tore it wouldn't start on petrol either

Yeah, but that tear you see on the gasket near one of bolt holes can be easily fixed with gasket sealant.
It tore apart 'cos I was bit clumsy when I was pulling it out. It shouldn't have happened if I was bit patient.
Diaphragm in the second picture is cosmetically in pretty good condition.
Thanx for the tip about the small leaks.
May be it was having a small air leak(but couldn't smell any leaks or couldn't hear any hissing either)
If you look at the around the gasket on the same diaphragm, it does look like it was kinda wet and may be it was leaking.
I reckon I give it a good clean and put it back together with good gasket sealant and see how it goes.
I got nothing to loose but can save $85 by doing that.
Yeah, I like the idea of keeping a spare one all the time. I keep a spare dizzy, ignition coil, carby, plugs, ignition leads, etc etc.
Hopefully this converter come out good without having to rebuild it with a kit. Brand new converter is around $220.
So, I reckon $85 for a rebuild kit kinda too dear.
Yours failed on petrol as well, probably 'cos it's EFI and that must have confused the switch over mechanism via the LPG ECU or the backfire must have stuffed up the petrol side of it as well.
Cheers mate.
Dom

[NissanGQ4.2]

I reckon I give it a good clean and put it back together with good gasket sealant and see how it goes.
I got nothing to loose but can save $85 by doing that.


As you say nothing 2 loose. Mine actually blew out so there was a good 2cm split between the yellow and black section, I just super glued them both back together and it worked perfectly :)

[dom14]

As you say nothing 2 loose. Mine actually blew out so there was a good 2cm split between the yellow and black section, I just super glued them both back together and it worked perfectly :)

Yeah mate. I've seen a bloke dismantling an Impco model L on youtube. Inside looked horrible. It was full of crap and the diaphragms were all stuffed. Mine doesn't look anything like that. I reckon, with some luck and patience with putting it together,
I should hopefully be able to get it going.
If it runs when I put it in, I'll leave it on and keep the secondhand one I bought from the wrecker as a spare.
I'll keep you updated. I'll clean it tomorrow, give it a day to dry up and fit it in on Sunday.
I will post the outcome.
Cheers
Dom

[threedogs]

go over all the gas connections with some soapy water, when its running.
see if that shows up any leaks, dish washing liquid will do mixed with a bit of H2O

[dom14]

I finished the "rebuilding" of the converter. I haven't fitted it yet. The carby started giving me bit of crap, so I had to attend to that. I'll fit the converter tomorrow and see how it goes. There are plenty of pictures that I need to post here as well. I need to edit them first.

[dom14]

BTW guys, avoid using carby cleaner or petrol on the rubber diaphragms.
The already worn out rubber diaphragm on the low pressure side and the rubber gasket in the high pressure side didn't like petrol(it appeared to be damaging it more). So, I reckon carby cleaner is not good, if petrol is no good. soapy warm water is the best way to clean anything rubber. Petrol or carby cleaner is ok for other parts, including the low pressure top(orange colour) diaphragm, but I would still use kerosene or warm soapy water on that diaphragm as well. It's better to be safe than sorry.
If you are using a rebuild kit, then non of the above applies. :)

P.S. Use warm soapy water with a soft tooth brush to clean the diaphragms.

[dom14]

Here are the pictures of my "rebuild" job on the Impco model L converter.
Pictures are in order(for the most part).
As you can see, the rubber gasket on the high pressure side(where the liquid gas enters the converter) is bit tarnished.
I simply reversed the sides of the gasket and hope it works.

For detailed list of the Impco model L converter parts, refer to the PDF document in this link.

http://www.teecoproducts.com/catalog/PDF%20Files_Catalog/IMPCO/IMPCO%202006%20CAT-Model%20L%20Series.pdf

[dom14]

This is the Impco model L converter illustrated manual

[dom14]

I'm yet to fit the "rebuilt" converter to the vehicle.
I will let you guys know how it goes once I've done that.
ATM, I'm stuck with the carby issue, so I had to prioritize that.