I've been having lpg problems with my tintop recently.

It was missing on one cylinder on lpg but not on petrol. I had a new injector fitted and it ran well again for about 100 miles. At this point it started hunting and often cutting out at roundabaouts (only on lpg). Now it runs ok for 50 miles on lpg from a freshly filled tank but after this the lpg system shuts off as if it is out of gas. The pressure lights (hghly inaccurate) are still showing 3 of 4 so there is still gas present.

Any thoughts?

Not had a lot to do with gas installations but could the problems be due to cold weather?

LPG is very harsh on rubber, if the system is a couple of years old you probably need to replace the diapham etc in the vaporiser.

I had to do this a couple of times, never had any issue with cold weather.

Regards Mark

yup i was gonna suggest vaporiser. Could also being the pressure valve. Trouble with LPG, all problems cause same symptoms

The LPG fuel gauge works on a float switch in the tank not pressure --- pressure in the tank is the vapour pressure of LPG at ambient temperature.

Is the system OEM or after-market ?

Assuming after market -- OEM systems are a bit different.

LPG demands a higher voltage at the spark plugs than when running on petrol hence is much more dependent on the condition of the ignition components.
Platinum spark plugs don't work well in LPG fuel engines either conventional copper core plugs changed every 10,000 miles or for long life plugs NGK Irridium, in both cases the gap should be reduced by 20% from the gap recommended by the manufacturers for running on petrol.

With after-market systems the wet and dry LPG filters should be changed every 2 years/24,000 miles, and the injector blocks cleaned with mixture of WD40 and paint thinner. The condition of the gas hoses and replaced as required. The water hoses and connections should be checked.
The electric wiring should be carefully checked for chaffing and the security and condition of connectors.
The main front to rear and filling pipes should be checked for condition and security.
Every 3 years or so the pressure regulator should be overhauled with a new diaphragm.
The system should then be checked for gas leaks and diagnostic dongle connected to check for logged faults , that the temperature and pressure sensors are giving plausible readings. The gas map should be checked on road test.

[Edited on 30/11/12 by britishtrident]

Thanks for all the info. I'll book it in for a full service and check as it's been converted for about 6 years and 90k miles!