my 1985 500 sec does not want to start when warm it has no problems firing up when cold but drive it 5 miles and it won't start , it has plenty of battery juice and it will start after 30 minutes or so, please advise, Terrio

t:

What is your history with the car? New to you? Had it a long time? Did the problem come on gradually, or suddenly?

i had owned for 10 years but never really drove it,at first it was my sons car now for the last 4 years or so my sister-in-law uses it and it seams to have suddenly started this problem

If the car has been in regular, near daily use, the first item to be checked for correct operation is the control pressure regulator (aka, warm up regulator [WUR]). If the control pressure is too high after the engine is at normal operating temperature, the mixture will be too lean when a hot restart is attemped.

i will check it out, thanks

would this be the part ?
1985 Mercedes-Benz 500SEC Base Coupe - Fuel System - Page 2

Nope; that is for the next generation of the injection system.
It does look like this:
Mercedes Warm Up Regulator Bosch 0438140068 Fit 380SL*380SEC*450SL*450SLC*500SEC | eBay

Prior to considering a replacement of a somewhat expensive part (the WUR), the o-rings on the fuel pressure regulator (FPR) should be inspected/replaced. The FPR is located on the side of the fuel distributor (FD), and has a hex head/cap.
Are you performing work yourself, or relaying these comments?

i will be doing the work myself