This is the second time this has happened and I do not know what the mechanic did the first time. I changed the oil and there was no problem, but I drove about 300 feet and shut it off. In about 10 minutes I came back and tried to start it. It would crank over well, but it would not start. All electric systems seem to work well except there is no fire to the coils. Can you tell me what keeps the fire from getting to the coils?