Hi Mark,

Thanks for your input. However, this thing stopped when it was on LPG and refused to re-start on petrol so I am thinking it is something common to both types of fuel system rather than petrol which your tests are suggesting. I am going to look at the ignition side again as you have suggested although I am seeing a nice HT spark both physically and through the Crypton HT Tester, Also, in my experience I have found that if a vehicle fails to fire on a "sniff", then the fault is usually either ignition or mechanically related. I just find it odd that it now fires with the throttle body blocked off which would perhaps indicate a very lean mixture but no obvious air leaks are present. Also, because the spark plugs are very inaccessible it was difficult to see if there was a serious over-fuelling issue going on. This will be checked on my next visit.

Regards

Pete M