help needed with my s2 ive just put it all back together and tried to start it, it coughed and splutered and ran for about 30 seconds then stalled and wouldnt re start it has a spark but doesnt sem to be getting fuel to the injectors ive cracked off the main fuel feed into the metering head and there is fuel there, ive tried another metering head and didnt start but dont no if either of the metering heads are any good any help please