ISX Injector Leak test

[JB Farm]

Hello all, first time poster. I have a CM870 setting on the floor. Engine is out of a wrecked truck. The owner said he was told this engine had a bad injector but it did not get repaired before being in wreck. My question is with injector leak test. Can I perform that test with engine on the floor? I know I can do the test but will it be accurate? I've always used the starter to see if there's leakage and then barred engine by hand if I had bubbles. Does the engine need to spin faster to initially check for bubbles?

[Rawze]

depends on how leaky the injector is. Also, not sure how the test would would go with IFSM, etc. starved of fuel.

[JB Farm]

Ok, thank you. I also have a question about the bubbles the may show up. Is this from compression getting past the injector bottom seat? Is the injector stem being crushed into the bottom seat the only thing that seals off compression? Or is there a check valve of some sort? Just want to understand the system a little better.

[Rawze]

(06-08-2025 )JB Farm Wrote:  Ok, thank you. I also have a question about the bubbles the may show up. Is this from compression getting past the injector bottom seat? Is the injector stem being crushed into the bottom seat the only thing that seals off compression? Or is there a check valve of some sort? Just want to understand the system a little better.

Both ... Bottom seat (if the overhead is out of adjustment), and a check valve inside the injector that wears out.

[JB Farm]

I didn't have any luck getting bubbles to show up. I think I'm going to replace them all. If one is bad, the others maybe aren't far behind. Am I correct to say an injector can be bad but not produce bubbles? If the injector has the bottom seat sealed good, I'm assuming there's still other failures that happen. Leakage between metering or timing portion of the injector to where you don't get the hydraulic action that's needed? Just curious is all, I'm assuming Insite would detect that type of failure also? Throw a code?