i have a snap on scanner at work and hooked it up to my truck and ran a test that shuts off one cylinder injector at a time, ive never done it on a common rail and was wondering about the results. when ever one cylinder got shut down the RPMs started fluctuating up and down really bad from anywhere around 650-1700 RPMs with no throttle input. is this suppose to happen? and if its not does anyone know what is happening?

 

rpm should drop somewhat, not a lot. when you have no drop in rpm you've found the dead inj

 

Are you using a 8.2 MODIS ELITE INDUSTRIAL? That's a nice scanner but expensive, may need Cummins software update which is also very pricey.

 

that makes sense, i dont think we have that