My guess is that it's an electronic problem. I don't know the 603's injection pump but if it gets hot and quits I really think it's something electrical. I don't know why mechanically heat would mess up your injection. I know on my 603 there's a bunch of electronics on the back of the pump. I don't know if it's got any solid state stuff in that pump but if so, solid state devices only last so long under heat. Think about your computer's microprocessor. When it over heats your computer A. Turns off or B. Breaks.

So... That's my guess. The dealer told me the electronic stuff is emissions related. I don't know but I do know that electronics can wear out. I'd look into it. Maybe talk to a dealership in a large city about your problem. See if they know anything. GM's 6.5 liter diesel had many many heat issues on their injection pumps. Get hot and wouldn't start. I've not heard this much with MB's bosch pumps but it's possible. Maybe.

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