I'm dealing with the same type problem. replaced a faulty/leaking water pump yesterday & car ran fine afterward but will not start this afternoon. Good spark out of coil but just cranks & does not start. Sometimes upon releasing the key after cranking the engine trys to run backwards. Do these Optispark units fail after a leaky water pump or do I have a moisture problem that I can dry out or repair. Started fine & ran well after water pump install 3 or 4 times & road tested well but that was yesterday & will not start today.