I HAVE THE SAME PROBLEM JUST NOW!!!!
been at it for weeks i could take both 2 an 3 plug lead of and makes no difference!!!

now it wont start at all just spluttes once in a while
the plug on my temp sensir has been changed at one time?? would it matter if the wire's were the wrong way round??
i also dont have an earth strap on my emgine goint o fit one today that might be an issue on yours matey??? but again could be the cap etc etc etc