I am having a VERY erratic start problem. 99% of the time it starts on the 1st revolution. In the last 3 months have had several instances where it starts but dies after 1 or 2 revolutions, then only cranks over & gives no indication of starting. After repeated attempts or waiting a few minutes or overnight, it will start as usual & run fine. Have run diagnostics. Only get a C553 history code, no other codes. Thinking maybe a bad relay, but which one would it be? I have done the Delco upgrade, but have not yet switched to Rapidfires; but I do not think that is the problem. Any suggestions?