Could it be "vapor locke"

[ptruty]

After two years of sitting idle got a major tune up for my 1964 230 SL.  Runs like a swiss watch.  After a long run 30+ minutes or stopping to refuel, I cannot get it restarted until it sits for 30-40 minutes.  Has anyone had this  problem?  It is very frustrating and leads to distrust on taking it for much needed drives.  It has always had this problem.  Help?

[glenn]

Sounds like the 'crud in the tank'.   Crud blocks the refilling of the quart sized plastic vessel in the tank.  Do a 'search' for a mountain of info. ..

[ja17]

If you have fuel, and spark the engine will start.  Check for spark first. New ignition points sometimes "seat" and close up. Re-adjusting them solves the problem. If you have spark, try a shot of starting fluid to diagnose the problem. If the car start right up your problem is fuel related.
Keep us up to date.

[enochbell]

...and if you follow Joe's diagnosis and find that the shot of fuel works, then you can remedy by adding a manual CSV actuator.  I had the same problem in my '64, it would not start "hot" (after running for 10+ minutes).  I just installed a discrete (under dash) pushbutton wired to the CSV to allow momentary actuation of the valve.  Problem solved...inelegantly...but solved.  I believe this problem is common in early 230sl models, and that later versions of the starting systems corrected for it.

g

[ctaylor738]

You may have a slow-turning starter contributing to the problem.  They draw a lot of current, leaving little for the ignition and the fuel pump, and the mechanical pump is turned too slowly to deliver enough fuel to get past the vapor lock. 

I worked on a 250SL with this problem, and a rebuilt starter cut the hot start time from 10-15 seconds to 2-3. 

The solenoids on these starters have a terminal to output battery voltage while cranking, so you can run a wire from that terminal to the + side of the coil to provide a hotter spark when cranking.

[ja17]

Also the later W113 starters had 40% more horse power than the early starters. Use the later starter if you have a choice.