This has been happening on and off for the past 2 years on my 85' 240! During warm or hot weather, and mostly after a long drive(30 min or more) you turn engine off,then I try to restart by turning ignition key and no crank! The new Bosch starter is 1.5 years old and I just replaced the ignition switch from the junk yard two months ago when the same thing happened but did not solve problem! This has happened a half dozen times and with same warm weather long drive conditions, and every time if you wait it out, it will start again like nothing has happened( sometimes 20 minutes and a coulpe of times an hour). The connector in the firewall is good, I always check that when this happens (disconnect reconnect) still no start! The ground wire is tight and looks fine, I only see one on the rear of the cam cover. Is there another that I don't see? Any help is greatly appreciated!!