thanks guys for the replies. The filter (as I recall it was the one that scewed into the injector pump at the end of the supply hose) was plugged solid with what appeared to be bits of black rubber. This was back in the spring when it was doing the same thing but worse and then would not start at all. I have since replaced all the seals on this supply line and checked this same filter a few times (always clean), tried other fuel and tried removing fuel cap.
As I recall the supply line comes off the side, near bottom of the tank. I am going to check to see if there is a pick-up in the tank that may have cracked, broken or fallen off. It has occured on a full tank but seems more common
when there is less fuel? A few times when removed the cap durring this problem there seemed to be a vacuum behind it?
I have also read that a clear line installed on the return side will show if there
is an air leak so I may try this after.