'79 450 SL - Vapor Lock or Fuel Accumulator?
 

My '79 450 SL has many of the symptoms others have described in this forum. Difficult to start at first, much easier to start after the car has been running awhile. The longer the car has been turned off, the more likely it will take 5 to 7 seconds to crank the next time. Once it starts it runs rough for a few seconds and then is fine. In the past 6 months my mechanic has replaced the Starter and Fuel Distributor, cleaned the fuel injectors and replaced the fuel injector seals. I've tried the suggestion of turning the ignition on and off rapidly to pump cooler fuel, but no luck. Any idea if this is more likely Vapor Lock or a worn out Fuel Accumulator? I like my mechanic but this one has stumped him, so any suggestions on how to diagnose would be great (plus the problem never seems to act up for the mechanic).