I have a 1977 450SL (California emissions compliant). It's fuel injected, and I usually have no problems starting it up from a cold start or after it's been sitting for more than two or three hours after running. Also, I can readily start it after i'ts only been sitting for up to 4 or 5 minutes after i'ts been running. But anything between 5 minutes and 3 hours requires lots of cranking and throttling to get it started. It seems to be purely a function of time. I've seen another 450SL with this same problem, leading me to believe that I'm not the only one experiencing such difficulties. What's happening? Is there some sort of vapor lock that is occurring (possibly from a catalytic converter)? I would love to hear any suggestion and/or any solution to help alleviate this symptom. I'm on my third battery in 5 years and already had to replace the starter as a result of this excessive cranking.