Cutting out after LPG fill up

[KarlosFandango]

Hi,
Had my 1.9DG van for two weeks and she has been running perfect on petrol, not that i have gone far as just replaced the alternator but she started and idles perfect. I just filled her up with LPG as it was converted. I took her out on a flat road, got some speed up and pressed the button to change over to gas....thats when things went wrong. She started to struggle with power and cutting out so i pressed the button to go back to petrol. She drives fine now but cuts out as when dipping the clutch and the engine idles at a junction. Got her home my keeping revs on and left foot braking. I have let her cool down (thinking choke problems) as i was driving around for 30 mins on petrol before without problems. Now she starts first time no problem on but cuts out as soon as there are no revs on the engine. The gas has done something but i have read the wiki and archive and can't figure out what it could be. I have checked pipes and electrical connections. Do i now start taking the choke and carburettor apart? Why would it now not work after trying the LPG?
Cheers.

[waltraud]

What sort of lpg system do you have?

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[KarlosFandango]

The certificate says OMVL system.


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[Mocki]

sounds like the petrol switchover is at fault, had it not been run on LPG for a while?
its possible the fuel cut off solenoid for the petrol is sticking, either fully or half open, mking it run on both fuels when you switch to lpg, so too rich a mixture , and not enough petrol when not on lpg
there should be a manual switch or thumbwheel on the petrol solenoid in the engine bay , operate it and keep the lpg switched off see if it solves the petrol running issue .

ideally take it off and service it , its just an electrically operated tap .
do not mess with any lpg or petrol or choke settings, its not your issue . everything was fine untill you tried to switch to lpg, so its there where your problem lays

[ajsimmo]

Two things spring to initially mind.
Firstly, are you familiar with the method of switching between fuels? I ask because incorrect technique could give the impression of poor running immediately after switching to LPG (I wonder why you hadn't previously tried switching to LPG during the two weeks of ownership). If yes, then there's a fault when running LPG that needs addressing but it won't be the cause of your petrol issue.
Secondly, because when you switch to LPG you turn the petrol off and run the carb dry, if there was any sediment in the float bowl this would be swirled up into suspension upon switching back to petrol, and dirt could then lodge in a jet, causing the symptoms you describe.

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[KarlosFandango]

I am not familiar with the use of LPG. I have requested more info from the lad I bought the van from. It hasn’t been run in LPG for a while and the tank was empty. The switch looks like this:




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[ajsimmo]

You said you pressed the button to switch to LPG, but you didn't mention the two presses necessary to achieve this. Did you switch petrol off, drive until you lost power, then press again to switch to LPG, or do something different? I ask because if you pressed twice too quickly you may have been running on both fuels which would feel just as you describe.
As for the petrol fault, if you have access to an airline you could remove the carb top "pancake" and blow down the three brass "jets" you see in a row. Or use a can of carb cleaner (with the plastic straw sprayer) to blast it clean. If it then runs ok, there's muck in the float chamber and the carb needs to come off for splitting and cleaning.

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[KarlosFandango]

I took the pancake off on everything looks extremely clean. A night of research on conversions and carburettors, VW T25 Sir Adventure Blog has a very good strip down video.
She now starts and idles on petrol so hopefully no strip down required. You hit the nail on the head about the petrol to LPG change over. So I’m going to try again.

Running with the petrol light on, press the button once, no lights on, drive till loss of power then press again to illuminate the LPG light.

This method removes the petrol so the carb is dry then introduces the LPG. (I have been driving successfully without this petrol light illuminated on the switch which should mean no fuel, plus the other lights showing how much is in the tankare not illuminated. I put £10 of LPG in)

I’m assuming I cant test this on the drive and I can’t start on LPG? I have read that it’s possible to start on LPG and have both fuels running with the system changing over automatically.

My system was installed 2006 so I’m going with start on petrol, starve the carb, introduce LPG.

Thanks for your help. I’ll let you know.


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[KarlosFandango]

So it was down to the wrong operation of the change over buttons. Changed over really easy today. Now I have to fix the stalling at idle on the gas.


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[Mocki]

any of them will start on LPG from cold, providing they are set up correctly.

when you start on LPG from cold, put your foot on the throttle pedal then turn the key on, wait for the LPG light to all come on , and you will hear the tank relays "clank" then turn the key to start the starter . ( lpg "squirts" a dose of lpg into the carb when the lights come on and the tank relay operates and you need to have the throttle pressed so the choke flap is open fully and lets it in ) as soon as it fires take your foot off the throttle
try it .... run home on lpg, dont switch to petrol and see.
just be aware that if you dont have a electric petrol pump, you will need to crank the engine over to get petrol up to the carb if you cant get it to start on lpg