Have you changed the spark plugs? When I first got mine, I thought it had the wrong plugs (from the number) bought new quality ones for a 2l Pinto, put them in and had similar problems, put the old ones back in and it was fine after that. If you are low on fuel, could be something floating around in the tank and blocking the outlet, but it sounds like you have filled it. Back in my Triumph car days, I am sure I had similar problems when coils aged and broke down.