Runs great on LPG but stalls/won't idle on petrol. Ideas?

[pfillery]

Recent conversion, runs perfectly on gas, switched over to petrol prior to getting home yesterday and it stalled. Assumed I was out of petrol so put a top up in and does the same. Yet if I switch over to petrol while driving as long as I don't drop it to idle she goes fine. My driving habit is to start on fuel in the morning, switch over to gas after a couple of minutes and then start on gas at work to drive home, switching to petrol around the corner from home so its ready to start on petrol the next day.

Assuming I can eliminate fuel pump, fuel flow and shutoff solenoid (since it runs normally when driving) and can eliminate ignition issues since it runs and idles fine on gas, what am I missing or where should I look? The vehicle is just about due to go back for the 1000km tweak after getting the gas put on 2 weeks ago, but I'm figuring since this has only just started to do this is more a carby issue than anything to do with the gas.

In case it is relevant, it is a 186 red motor in a series 3. Carby not injected. Been running on fuel fine up until yesterday. Blockage? What do you think?

[bee utey]

Check the two philips head screws holding the main body to the throttle body, they often come loose after adding a gas adaptor. Doing your overnight soak on petrol is the worst thing you can do for the carby, cyclic drying out of used gaskets is the quickest way to weaken them. Purchase a carby gasket kit, install it, and start it on gas in the mornings. Keep the petrol for the open road.

[pfillery]

Check the two philips head screws holding the main body to the throttle body, they often come loose after adding a gas adaptor. Doing your overnight soak on petrol is the worst thing you can do for the carby, cyclic drying out of used gaskets is the quickest way to weaken them. Purchase a carby gasket kit, install it, and start it on gas in the mornings. Keep the petrol for the open road.

Thanks bee utey.

Do you mean the steel bit at the bottom of the carby with the throttle butterfly valve in it? I don't believe this was touched or undone during the install. There is a gas ring hooked up to the converter and it is fitted to the top throat of the carby (standard stromberg) with a couple of small grub screws, then the air cleaner hose elbow (standard land rover type air cleaner) is fitted onto that. I'm wondering how this would effect starting with the choke since the gas comes into the system above the choke.

Funny that I was told exactly the opposite of what you said about running it on petrol, by 2 or 3 other gas installers, including the one that fitted the kit. They are all telling carby car owners to run on petrol just before you get home then start on petrol the next day. I have found it starts just that little bit easier on petrol in the early hours of the morning when it is cold.

You say to save petrol for the open road, but why would you worry about using it at all if you don't need to start on it (unless of course it runs out of gas)? 58c a litre for gas or $1.40 for petrol doesn't seem like a hard choice. I've been getting pretty good mileage out of the gas so far.

[bee utey]

If you ask what I mean by throttle body and you say the thing with the throttle butterfly in it well that's what I meant. Just check the screws please. They come loose because of vibration, more weight up higher and shrinking gaskets.

As far as the petrol goes you have to use up the petrol before it dies of old age in a vented petrol tank, so you need to replace it with fresh fuel within 3 months maximum if you want to keep the petrol system healthy. This is best done by a 10 minute run on the open road once or twice a week.

The business with leaving petrol in the carby overnight is one of those myths handed down from mechanic to mechanic, I soon worked out it was a waste of time, carbies still fail (2 weeks and yours is doing it already). Do what you want to by all means but if you work out how to best get it started on gas only your engine oil will stay much cleaner. Like I said, fit a new gasket set if you want the carby to last longer.