My 84 euro 500sel had an issue w/ starting when warm but started well when cold. And on start up it wouldn't rev up until it ran for at least 10 seconds. Sometimes when hot i'd have to crank on it for at least 5-12 seconds. Quite embarrassing. It also kind of had a lack of power. Goofy me i gambled $100.00 took it to the closest benz dealer and he said fuel accumulator. Well the issue was the fuel accumulator was leaking back fuel pressure into the tank. Thus we weren't getting enough fuel. He temporaryily clamped the hose to the accumulator and it immediately had like another 10 horse and always started up and ran great. So i immediately removed the clamp and put a good accumulator on it. Hope this helps.