560SEL- hot starting trouble
'87 560SEL 322k miles in really excellent shape. Problem is, does not start or idle well if hot. Example: Run to store for oil and filter. In store ten minutes. Come out and car will crank forever if you just turn key (cranking speed good). To get it to start, turn key on for 20 seconds (seems to help, but not sure), hold pedal at least half throttle, start engine. Maintain 2000 rpm for minute or two. Engine may or may not start ok. Will probably be running rich-real rich, lots of black smoke. If you forget, have to hold pedal to floor and let car run at 500 rpm until it clears its throat (it seems). That can take several minutes. Car starts great when dead cold. Seems to start ok if sitting for an hour or so. This happens in dead cold of winter or in warm weather. I tried replacing the OVP relay, but it did not help. If vapor lock or low fuel presure, I would expect it to be lean, not rich. New plugs did not help. I am befuddled. TIA.