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VS Dual Fuel - Stalling on LPG only

RUN415

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Car runs fine on petrol but stalls on LPG under braking or turning corners.
Used to be occasional but is getting worse...now surging/stalling at 60 kmh.
No problems when doing 110 kmh.


Ok, read lotsa threads can't find a definitive answer...could be lots of things.
Leads, coils, IAC valve, converter ???


Before going to a mechanic for a diagnosis...I thought I might clean the throttle body and IAC.
BUT...if these were that fouled...wouldn't it affect the running on petrol as well???


Sorry if this is a stoopid question...and any help appreciated. Cheers.
 

Jxfwsf

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LPG is more picky than petrol when it comes to running in an engine (just because it run's fine on petrol doesn't mean it will on lpg if the plugs are fouled slightly or the leads are old), start with the basics, how old are the plugs and leads? if unknown or old replace them first.

What sort of lpg setup is it? impco style complex mixer with simple converter or a simple gas ring mixer and complex converter?

When was the last time the lpg got a tune? it's not uncommon for them to waiver in their setting and require a tuning.

Does the check engine light come on at all while it's running or being driven? if so have you checked fault codes to see why?
 

mudfish

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As jxw said, check your codes first and foremost. Also, check the integrity of all your hoses/lines to and from your mixer/converter. LPG is very sensitive to vacuum leaks.
 

RUN415

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Thank you for the replies JXW and Mudfish...all valid advice which I have taken onboard.
The LPG system is IMPCO circa 1995 - variety unknown.

Will have another look over the weekend...will re-check the codes, check for vacuum leaks and
clean up a few things with TB/Carby cleaner.

I'll post back with the results and/or when the issue is finally solved.
Thanks again.
 

Jxfwsf

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make sure the hose from the mixer -> solenoid -> converter is good and not perished/cracked/fallen off, let it idle and by hand rev it up a bit by hand @ the tb, is the solenoid clicking? Put your hand on it and you should feel it and/or hear it, these commonly wear out and if it's not sealing it will be leaning the gas out when backing off the throttle..... maybe (if it's not clicking then it could be the opposition and just leaving the converter a atmospheric pressure and running rich)
 

RUN415

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*** UPDATE ***
Took the car to a mechanic...first thing he noticed was how tight the throttle cable was.
He maintains the cable should be fairly loose and have a fair amount of play in it.
So he slid the cable out of the bracket just before the throttle body to free it up a little...
...which is, incidentally, the way it was when I bought the car.
This means the cruise control no longer works but it doesn't stall so much.
So problem not really solved but it is somewhat better.

Thanks for your help.
 

Demonica

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Wtf kind of dodgy mechanic did you take it to?
 

RUN415

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lolz
I guess I shoulda explained...
The mechanic was busy and just had a quick look...completely free of charge.
No complaints here.
 

apollo13

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The converters are mounted sideways, as they have a diaphragm which would move under heavy braking. If you like cornering with the tyres squealing, then the lateral g force could upset the converter.
Also check spark plug gap. If it has 1.5 mm (for petrol) it will probably misfire on LPG.
 

Jxfwsf

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The converters are mounted sideways, as they have a diaphragm which would move under heavy braking. If you like cornering with the tyres squealing, then the lateral g force could upset the converter.
Also check spark plug gap. If it has 1.5 mm (for petrol) it will probably misfire on LPG.
lol, they are mounted sideways most of the time because there is no room to mount them any other way... gas pressure, the springs and engine vacuum are far greater at controlling the diaphragms than any style of driving you do.... unless you're doing mark 1 with barrel rolls and loops then it might have some effect on the few grams that it weighs.... but i think you'd pass out from the G's before it had any effect on the converter.

No, if the plugs, leads and other ignition components are in bad condition it'll misfire on lpg, the bosch platinum plugs i'm running that have done 30,000+ km's are still stock 1.5mm gap and doesn't misfire/backfire at all...
 
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