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VN V6 LPG problem

joe b

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I was wondering if anyone could help me with this problem. I have a 91 VN V6 Series 2 Commodore Executive Sedan with about 220 000 kms on it. I recently had it converted to lpg (a megagas system) for duel fuel. The problem is it sometimes stalls when you take the foot off the gas (when on lpg) and coast ie when you slow down for a set of lights, turn off, or anywhere really, which can be very dangerous. It seems it happens most when I get a straight stretch of road for a few kms then have to slow down. It is fine under power and I have no problems on petrol. I have recently changed the thermostat (it runs at about the second bar and opens about the third bar on the temperature gauge). When it has stalled, the gas converter is (usually but not always) luke warm to touch though the coolant hoses going in to it, and the thermostat housing are hot (the converter can be hot when driving normally around the city). It doesn't stall all the time when driving around the city, only occasionally when coasting. I've taken it back to the fitter and our efforts haven't been successful in fixing it yet. The next plan is to replace the converter. I often have to crank it over more than when on petrol to start, particuluarly if it is warm. The l.e.d. gas gauge can sometimes go to red even when I have 3/4 full tank too, though this is the least of my worries (I was wondering if it was something to do with the electrics). Has anyone had any similar problems or any ideas on how to fix it? Any help would be appreciated. Thanks.
 

JD

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take it to the place that fitted it and explain the problem they should be able to help.
 

FXST01

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Does your have the gas fitting between the throttle body and the air filter tube?

Mine used to do the same as yours, but i cleaned the fitting with carby cleaner and checked for air leaks around the fitting. Been good ever since until i took the gas off.
 

joe b

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yes it does fxs. I'll mention it to the fitter. Was yours a new system when this happened or an old one?
 

FXST01

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Mine was on the car when i bought it, but the problem happened a good while later. The gas fitting was black as
 

383 hatch

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Does it have a CAI by any chance?? Sounds like it needs a balance tube between the convertor & CAI. A balance tube is needed when the car is fitted with a CAI and what it does is apply positive pressure to the diagphram in the convertor to balance out the pressure difference between the CAI & convertor on deceleration! In some circumstances a balance tube can be needed even without a CAI.
 

andyli

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switch

hi, I got the same car like yours 91 s2. got the same problem. it stall on gas. the gasman change the gas converter(300), but does not work. adjust it, no. I sent the car at last to Holden and they check the problem, it is the gas and petrol light comes together. that means they come to the engine at the same time. aas soon as I show it to the gasman he knew the problem, it is the small switch under your steering wheel which control the gas and petrol. I do not know if he knew it before he changed the converter.good luck.
 

joe b

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I'll let the fitter know about it VN Calais, and andyli. Getting the converter changed next week. If that doesn't fix it, might take it to another fitter to check the system is installed properly.
 

joe b

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Success! (so far). The fitter changed the converter. There is a (recovery or balance?) hose going from the converter to the airbox which provides a vacuum and draws the diaphragm in the converter out to provide the right gas/air mixture on deceleration. The first converter put in had the opening to fit this hose at the back and was not hooked up as the back of the converter was bolted to the car and so the diaphragm was not being drawn out, therefore not enough gas was getting in, hence the stalling. The new converter has this opening on the front and so can be hooked up. No more stalling so far. This might be what you were talking about VN Calais?
 
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