diaphragms, human vs mechanical

[kz1000a]

Is it possible to ruin a gas convertor by applying lung pressure/vacuum to it?

Back in August I had to replace my LPG Aussie B2 convertor, cos it was stuffed. (thanks JC members for the help with that one!)
Since then I have a very slow water leak and traced it back to the convertors plastic water inlet fitting. I went to tighten it just a wee bit more and the (insert favourite expletive here) snapped off.

On Saturday I removed my convertor from the engine bay so as I could replace the 2 plastic water inlet / outlet elbows. Both were quite brittle internally.
Whilst I had the convertor out, I refitted the 3/8 inch? brass gas inlet and 1inch? plastic gas ouput with some proper gas PVC / plumbers tape.
I wanted to test that the PVC tape was making an air tight seal, so I closed off the 1 inch gas outlet with the palm of my hand and, using whats left of my lungs, created pressure, then vacuum on the 3/8 inch inlet connector. All seemed good and airtight.

I drove the 30 km round trip to work on Monday, not a problem with the car.

On the way home from work on Tuesday, (drive like a pensioner) I suffered the dreaded backfire (first time ever after 15 odd years on LPG) and the
front end of the air filter box went to a better place.

Car continued driving home no problems on LPG.

Temporarily patched up the gaping hole in air box with gaffer. On the way home from work today, car backfired again and now she don't want to idle on LPG.
Will drive OK but not idle on LPG. Petrol seems to work well all round.

Is it possible to ruin a convertor by applying lung pressure/vacuum?
Or could it somehow be affected by the backfire.

Plugs are set at 1.5 mm.

Leads are 3 yr / 50k old.

Throttle body and IACV cleaned out 3 months ago.

Any thoughts appreciated.


Cheers, Mark

[thek]

not sure if you can break a converter with a back fire but I know you can blow out a mixers diaphragm.

[levymetal]

try the leads, they could be getting crap. it's good practice to change leads quite often just to ensure your ignition is tip top. how old are your plugs? dizzy cap? coil pack?

as above, backfires can damage the mixer. if it continues to run like arse, you may need to readjust the diaphragm or get a new mixer. the backfire won't do anything to the converter as the fire doesn't go that way. i don't think your converter is stuffed either, it's a pretty damn simple device... just lets the water go through to warm up the gas that's going through in a different gallery. nothing to it, can't have damaged it by blowing in it

i have a friend who gave me a good idea of creating a type of blow off valve in case of backfires, it involves a bolt, spring, washer, and piece of rubber. too much to type so i'll draw up a diagram soon, but it ensures that if a backfire occurs you don't blow the crap out of your airbox!

[centy]

the human lung ca only produce a couple psi of pressure so not very likley.
The engine can run 3 psi negative with out any hassel.

[Cheap6]

If I read it correctly, the pressure and vacuum were applied to the LPG inlet to the converter. That sees tank pressure which will be around 800-1000kPa but up near 2000kPa(depends on tank temp.). I don't think that blowing into the LPG inlet could damage it! (It's a reasonable method of testing that the seals hold). Sucking on the converter inlet I don't know about (never tried it) but I doubt it.

Maybe try bleeding the cooling system again. If the converter is on the chassis rail or inner guard, it's probably OK as it's not the highest point in the system, although you might get an air lock if the hose inlets are at the bottom, but if it's up on the strut tower you would have to lift the coolant level high enough to fill the converter.

[Lost_Pete]

When we used to develop LPG and CNG systems we used to drill 3 or more 1/4" holes in the tube joining the airbox to the throttle body. We then covered the holes with electrical tape. If we had a backfire the backpressure would blow out the electrical tape and vent through the holes and hopefully save the airbox.

[kz1000a]

UPDATE

Replaced the leads $45 and plugs $26 and did a 380 km trip to venus bay this weekend and and all is well. (Diaphragm OK. impco 255 CA $90 AMR manufacturing) Cheers levymetal, reasonably cheap fix.
I can confidently replace airbox now.
Just for the record, cheap6 I was sucking and blowing on that convertor in any orifice that presented itself, so i was sure of sealing that mother up!
And a good idea pete, Im gonna try something along the lines of your suggestion. Its quite unreal how violent the back pressue can be.

Thanks yet again JC and members for advice sorting out.

Cheers, Mark

p.s any one tell me why can I see the "scales" (on the date header) when logged on and viewing my own posts, but I can not see the same scales in respondents posts?

or what I need (gas analyser wise) to keep my girl in tune?

[levymetal]

no worries mate, it's good to hear your car is all fine. basically keeping the car running well on lpg requires good ignition, and getting it gas tuned around once every 6 months. other than that you're sweet to go now.