I had some problems a while back with light blue smoke on start up a while back so i change the advance solenoid. then just recently the van ran rough for a very short period of time and then started running well again now it seems to be rough generally between part middle and high throttle idle is not to bad. now ive cleaned the tdc sensor (ive got a rev guage and this was working fine). I have noticed the pipe between the priming bulb and fuel filter gets full of air on a few occassion i have pumped the bulb and it seemed to help the running but then on another occasion it made no difference. i cant see much in the way of air running the hp pump (lucas mech part electric not epic) but i have a suspicion there might be some in the housing. i tried running it with the needle lift sensor and the tdc sensor disconnected and it did seem to run a bit better with some high rev knock though. it seems to have run differently every time i start it. and the smoke is generally light blue (not oil as it is not using any) but some times grey or whitish. there is never any trouble starting it other than the roughness. i am suspucious of the 'new' solenoid bought from flag diesel. any ideas?