That's pretty much the same deal as I have. Bit came from local Repco (the main T, approximately $22) and the other adapter that screws in to replace the standard 5/8 one came from Bursons (about $6).
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Bee utey, just for the sake of interest I removed the screw that was blocking the plenum vacuum tube to the brass tee. Idle impossibly rough and the exhaust was popping and farting. With it reblocked it resumed perfectly smooth running.
Yeah but is the big hose connected to the throttle or the air cleaner? If the air cleaner it will run lean and do exactly as you said. You know, sucking air instead of gas/air mixture? Also how big is the hole the screw was in? More than around 2mm and it'll suck much way too much air. If you have a pic of your setup it would help.
When changing breathers you may have to readjust idle mixtures and base idle speed, because it was wrongly connected before. Not rocket science.
Another update.
The big hose is connected to the LPG mixer not the air cleaner. I drilled a 2mm hole down the middle of another 3/16" screw to go in the small port on the tee (the port itself is threaded for 3/16" so too big). The idle was smoother but even with the idle screw adjusted to smooth it out, it doesn't drive as well off the bottom and the idle speed too high, especially with the timing advanced to where it is. I've gone back to the way it was - blocked. The conversion was done by LPGAS1 here in Melbourne and it's as it was when I bought the Disco, and the previous owner said it was left as installed.
Precisely. It's connected to the air only side of the mixer, where it is getting no LPG but is dropping fumes into the mixer. Open it up one day and have a look inside. They look real ugly after a few years of oily fumes.
Look if you're happy with it I am not going to argue with you but all of my comments from earlier still stand, with the exception that your MAF is probably safe. Your mixer and your IAC stepper are still going to get gunked up. The OEM location (on the throttle intake) for the big breather hose is still the correct one for this vehicle, whatever LPGAS1 have done.
Oh and if the idle speed is too high after fixing the breather, stick a 3/16 allen key in the manual idle adjuster on top of the manifold, and screw it down a bit.