CM870 won’t start when engines hot

[Rawze]

(12-20-2022 )MattSierraServ211 Wrote:  ...

And i am still getting air in the fuel return straight out of the module. Clear as day going in, air mix coming out. The warmer it is, the more air you see. i have multiple cummins manual books but the diag. for an air in fuel problem is as vague as can be.

Anybody got a suggestion that could direct me to the light at the end of the tunnel?? Lol

You may or may not have air getting into the fuel.. but Don't chase a ghost ...

The CM570, CM870, CM871 (any of the IFSM engines) return line off the IFSM that go back to the tanks will always have a little bit of bubbles. It is normal, as there is a small restriction in the main return line + a sudden pipe diameter change, that creates a bit of cavitation. It has no effect whatsoever on engine or its performance, and is quite normal. This has always been known and is NOT in the manuals for some reason.