Originally Posted by 930gutdr
I experienced the same problem. The fuel pump located in the fuel tank failed to start after heating up. The engine would start from cold. but not after running an hour or two and would restart after cooling 30 to 40 minutes.
I found the problem by calling a Mercedes dealer several hours down our route and had the engine attached to their diagnostic equipment before shutting it down. The fuel pressure in the fuel rail was 0 when they attempted a restart.
I believe it should be possible to hear the pump run for a few seconds with the key in position 1. No pressure = no start.
I don't think this is what the OP is referring to in the original post. The OP didn't describe the "no start" in detail but I think they're saying the vehicle would not engage the starter motor. That is, the engine did not "turn over." They turned the key to "on" and the dash lights illuminated. They turned the key further to "start" and nothing happened.
If that's the case for the OP, it makes sense there is some sort of defective safety feature or something that is interfering with the starting protocol.
I gather from your post that the starter would engage, the engine would turn over, but with no fuel pressure the engine would not start.