When you have problems remember to check the basics first.Start with a good visual inspection take your time paying close attention to vacuum hoses and wiring connectors (easy to do if you keep your engine clean)Do you have good vacuum (is the engine allowed to breathe) (is the exhaust plugged) (Is the engine in good mechanical condition, Tired)Do you have fuel pressure and volume. ( fuel volume is to often overlooked ) ( fuel filters can cause odd problems )Do you have a good strong sparkRemember if you have fuel and spark in sufficient quantity and at the right time it has to start.