What kind of pressure should you be reading on a "good" cylinder? At what point is pressure too low? Is pressure usually low when cold? (I know nothing about this stuff...)

 

Mine was around 380 psi@cranking rpm the last time I checked when I had all 6 injectors out. I don't know what would be too low though.

The real check is to see if all 6 are close to the same pressure. Mine were within 10psi in either direction.

 

My Cummins book is on loan to SteamDave at the moment, so I don't have the answer. Dave?

What JD730 says is right, you want them all pretty close to each other. The actual number will vary based on how healthy the starting system is.

 

Just curious - 5 of mine are at around 390 cold, one is at about 450. The mechanic seemed to think it was just fine and said that after warming up everything seats and the pressure goes up a little.

 

i think on just about any production motor +/- 10% is the range

 

5 seem fine im a bit worried on the other one shoul not be more than 10 %difference maybe his gauge is going bad or i hope not you got a broken ring on piston is your truck burning oil if so theres your prob oil get on top of piston raising compression or you could have a burnt valve but if i remember correct that lowers compression