help with my 2008 isx no start..fuel issue??

[Rawze]

CM871's are notorious for that "mystery no start" no matter what the h$ell you try scenario. -= Seen a lot of people go crazy over this trying to solve it.


First, it should be known that while electric lift pump is running, pressing in the compu-check test port ... fuel should come blasting out of it. Letting it purge for about 10 seconds usually purges most of the air in the pickup lines etc. -= WASH all the the fuel off the truck and engine with water and soap so that it is not a fire hazard after, if someone does this.

Next.. something else to keep in mind ...

Worst case scenario is during first crank right after an inframe. This would be where everything is bone dry including the insides of the injectors, head, everything. -= After purging the air out of the fuel like mentioned above... It takes a full 30-seconds long cranking session (the ecm/starter will usually time-out) .. then a 10 minute rest to let the starter cool off, and then a second 30-second cranking session during which it will fire off.

Here is a fine example of this in these 2 videos when we did Waterloo's truck here at my house...
first crank attempt: https://youtu.be/PpsfujvFKcM
second crank attempt, and it fires off for the first time: https://youtu.be/1hdRaSD9mqk


-== keeping that info in mind...



Here is what needs to be done for that no-start scenario from he#ll on them ......

A)> while the electric fuel pump is running.. press on the compucheck port .. fuel should come blasting out of it at high force. It also should not be full of air.

B)> Smack the top left corner of the ECM.. almost hard enough to dent its casing... if the electric lift pump cuts out or acts up when you do this.. THE ECM IS BAD!. The CM871 ecm's in particular are notorious for going bad and getting intermittent like this. This especially if the ecm is more than 8+ years old.. OR (more common) if some moron has never changed the crank shaft damper when it was due (according to proper maintenance schedule) ... and the constant engine vibration finally took it out.

B)> Watch the OIL pressure gauge in the dash while cranking. If it does not move a few psi above zero.. even after about 20+ seconds of cranking.. then the ECM IS MOST LIKELY BAD! That or the oil pressure sensor.. or perhaps oil pump itself.. but the most common issue for this .. is a bad ecm actually.


- You say you measured the pressure manually.. but you need to actually do this with the software instead ...

C)> USE the cummins Insite software to monitor fuel pressure while cranking. Insite should report more then 50 psi minimum or the ecm will not even try to fire off the injectors. Just for reference, most trucks will show 100+ psi when they are healthy. This needs to be verified. So if insite is reporting a low fuel pressure during cranking then almost always.. it is the gear pump shaft that has snapped internally.

* It can also be that the fuel shut-off solenoid has gone bad and not allowing fuel ... so removing the guts inside of the fuel shut-off solenoid and doing this check again is necessary before assuming the gear pump has gone bad.

NOTE: Ironically, when the gear pump internal shaft is snapped .. it usually will catch and make full fuel pressure if someone uses starting fluids to start the truck, so it fools you into thinking it is ok once it is up and going .. but it will not make proper pressure while cranking. Hence, using insite to check this. -== this is in fact the most common scenario of all with regard to in not cranking no matter what you try or replace.

D)>. Also make sure there are no crank/cam position faults in the ecm while your at it.

E)>. THE TURBOCHARGER.. as it wears out is known to hang up at 100% position and mechanically get stuck there. -= If it does this then the exhaust manifold will be choked off so hard, that the engine cannot let exhaust gasses out. This causes it to only stumble momentarily sometimes and die.. or simply not start at all ... or to only seem to rev up a few rpm after cranking, and labor against itself really badly. NOTE: The engine will likely also not run (or only run momentarily and die, or have revving up issues) even if you use starting fluids.

-= If the turbo being locked-up at 100% is suspect ... then someone needs to remove the turbo actuator off the top of the turbo and check the VG arm movement to ensure it is free and has full travel range. If it is ok, then an actuator install and calibration procedure needs to be done to get it back on properly.