Here is a challenge for all. I have a Freightliner M2 106 with the 260hp Mercedes. About a year ago I started having starting problems. This happened in both warm and cold weather. I replaced filters, checked wires and did everything possible. Some tech on the internet suggested I replace the check valve located between cylinder 5 and 6. I did this and at the same time bled the diesel at the injectors. I can not remember if there was much foam at that time I did bleed the diesel. I also unplugged both the computers and checked the connections. I basically fiddled everywhere. I started the truck and never had the problem again until two weeks ago. I did everything again as last time, except replacing the back flow valve. I do not think that it can be the valve again, as anyone rarely replaces this valve in the first place. I did bleed the diesel at the injectors thoroughly, bit there is lots of foam and I am not sure if this is air or just the pressure? I checked for leaks, and tightened everything a possible could. Once the truck sits for a couple of minutes it would struggle to start, 9 out of 10 times. Batteries are very strong. No fault codes. It definitely sounds as if it first has to build fuel pressure again. Could also be the ignition that controls the compression relief? What really baffles me and what I do not understand, is that, if I let the truck roll slowly and clutch start (manual) it, the engine fires immediately without any hesitation! Where did the fuel come from suddenly? Why does it start easy now? This mystery is beyond my understanding. Thank you in advance for any feedback. Kind regards.