CM870 won’t start when engines hot

[Hemiterry]

Recently my 2006 International with a 400HP CM870 has been having starting issues. In the morning when cold it starts up but idles rough for about 5 seconds and then runs fine. Today I turned the engine off after hauling for a few hours and cooling water temp down to 180 and tried to restart about 5 minutes later and it turned over fine but would not fire. I ended up using a shot or two of starting fluid and it fired up, ran rough for about 10 seconds and then ran fine down the road fully loaded. Later In the afternoon I was pulling onto the scale at the pit and the truck started idling rough and died. I managed to fire the truck back up barely and it skipped and sputtered but got me off the scale then died again. I waited 45 minutes and tried to start again, I cranked
On the engine hard and it fired up, idled rough for a few seconds and then ran perfect until the engine temp came back up and died again. I think it’s obviously a fueling issue but where should I start with my trouble shooting ? The electric lift pump sounds strong when you turn the key on and my fuel filters are brand new.

[Bengy88]

Any check engine light? Seen everything from injectors to an oring on a davco cause this. I would probably start by making sure there isnt an issue at the davco ( assuming you have one). Check for fuel leaks, verify fuel pressure when cranking, running, and while giving the problem, check for air in fuel……. That is if you are 100% positive that it is a fuel problem.

Also are the fuel filters new as in you put them on yesterday and your trucks taking a shi#t on you today? Or new as in you changed them after the issue began? May be somewhere you wanna check.

[Rawze]

The things that Bengy88 said.

It can also be the shut-off solenoid starting to go bad. Removing its guts and running without it for a few days would tell you if that was the issue. The engine should run fine and also shut down just fine with the shut-off solenoid guts removed. It is only used as a safety back-up and not for actually shutting off the engine. -c If the engine does not shut off properly with the guts removed then you have a leaky fueling solenoid.

And lastly, there is a 0.008" bleed-off orifice in the IFSM (integrated fuel system module) just for preventing hard-starts like what you are describing while the engine is hot. If it clogs up then it will do what you describe. here is a post from a long time ago that talks about it: http://rawze.com/forums/showthread.php?t...6#pid44656

as far as the rough stumble ... make sure the engine also passes an injector leak test with flying colors: http://rawze.com/forums/showthread.php?t...7#pid72957

[Hemiterry]

Sorry I forgot to mention I did get a low fuel pressure code. Thanks for all your help, I’ll get started and keep you posted.

[MattSierraServ211]

I am currently having much the same issue on the same engine in a KW. And i have already replaced just about everything you can regarding the fuel system. Had initially found an injector cup with a huge chip out of it, i do believe that was the main culprit of all the air in the fuel return we were seeing. So the head, all injectors, lift pump, fuel cooling plate, fuel pres. regs, metering and timing actuator seals, pulse dampner seals on back of the fuel module, etc. have all been replaced. 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

[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.