QuestionMy '72 Spitfire is incredibly difficult to start...many cranks and starter fluid and tweaking distributor needed. Once warmed up, runs fine. Timing chain replaced correctly. Ignition tuneup and timing does not seem to help. Carb rebuilt twice, temp compensator taken apart and re-assembled did not know how to set, guessed.
AnswerHi Dennis,
When an engine will not start you need to look for what is missing with no thought of what could be wrong. All piston spark ignited engines need only three items to start and run, Compression, fire & fuel. There are conditions on each but all three are easy to test. Compression can be easily tested with a compression gauge and the readings should be about 125 to 165 PSI and little difference between cylinders. Be sure to do the tests with the throttle open.
Fire (spark) must be close to the correct time and be strong enough. Timing must be set to factory specs and not altered unless the engine is highly modified. If there is still a sticker under the hood, those specs over rides what any manual states. The firing order must be correct too, which must be correct as you say it runs ok once running.
As for a strong spark, you can tell roughly by just removing a plug and put the wire on the plug and lay the plug on a metal part of the engine and spin the engine over and watch the spark. It should be a thick blue spark. (not in the sun light)
Fuel must be available to the combustion chamber in roughly the correct mixture for starting. This is much richer than the running mixture. An enrichment device on the side of the carb supplies the fuel for starting. If an engine does not start and requires spraying starter fluid or something like WD-40 into the intake to get it to start, then that enrichment device (choke) is not operating correctly.
Tell me what the compression readings are and set the timing to specs and if the spark is a wide blue spark look at the choke. Is it the older manual choke or is it the coolant operated choke?
Let me know,
Howard
