I purchased my Mercedes 1979 450 slc last year from California. Odometar doesnt work and its read 140000 miles. I fixed everything on this car except Hot starting , door lock vakum leak and RPM decrease from 1000 to 500 every time when i shift from Park to Drive. Somebody did new tune-up on this car (distributor, spark plug wires). I put new spark plugs, injector cleaner and fuel accumulator but I have hot starting problem from day one. Engine always start right away when is cold even if I dont start a car for a few months but after i drive a car and engine is hot it takes me few long crankes to start. It helps a little if I accelerate. Also I did little experiment and I bypassed black valve size of golf ball that is conected to the air filter. After I bypassed this valve it was little bit easier to start when is hot. Also before I bypassed this valve engine was "dieseling"(continuing to run after shut off). After I bypassed this valve engine stops "dieseling". I read a lot of posts about hot starting problems and it seems nobody have an answer for this problem. I instaled new fuel accumulator and I checked fuel pressure regulator for leak(puling out vakum line). It was vakum there and no fuel leak. Mr Stevebfl give to me great idea to tee pressure gauge to fuel distributor and monitor pressure. I dont have pressure gauge so before I get one I wanted to check If any of you ever fixed this problem because it seems like a common problem. Thanks for all your help specially to Mr Stevebfl