Turn on the cockpit lamp, does it shut off with the engine? if so, then your loosing one side of power or the other and it causes the electronics to turn off shutting the engine down immediately. My S185 was loosing the positive side at the fuse link above the battery, another had a bad ground. I used a DVM, start at the battery you'll have 12 volts, move the negative lead to the engine block. still have 12V? if so, you have a good ground then leave ground on engine block and start checking positive moving test to both sides of fuse and then maybe further following the wires. when you find the faulty connector, clean and re-terminate. Keep us posted.