I fly the Slick 540 powered by a modified IO540 from Barret Precision Engines with Slick mags. The fuselage is 100% carbon with electrical cables running from engine compartment to aft of the cockpit where the battery is mounted.
I noticed during my airshow season mid July that my hot start procedure had to be changed overnight. This is after 300+ hours logged on this aircraft. Slowly but surely it became worse and worse to the point that jump starting the engine between displays became the only way to get the engine started due to the small PC680 battery. When the engine is cold the starting is fine. During the past month the engine also developed a slight hesitation on cold start in the initial turning of the prop. On my last x-country to and from an airshow my battery of 2 years old stopped charging. Blaming the overworked battery.
New spark plugs,mag timing checked, new battery and following everybody's different starting procedure advice had no effect on this worsening problem.
After stripping and investigation I found that the Negative cable connection to the engine coming from the battery had a suspicious crimp and I was able to move the cable ever so slightly inside the opening of the lug.
After replacing the lug with proper crimping, my hot start problems vanished and battery is charging again perfectly.
I just would not have thought that a bad earth connection could have caused all these issues.
Lycoming, Continental, etc.