Isx Cm871 Injector leak test

[BC77]

Hello all. I preformed a injector leak test on my Isx. I got some air bubbles by cranking the motor and baring over the motor on the front actuator representing injectors 1, 2 and 3. The bubbles were between B and C indicating injector 1 is leaking. When I switched over to the back actuator representing injectors 4, 5 and 6 and preformed the test again, I got air bubbles while cranking the motor but none when I bared the motor over at least 6 complete revolutions. The air bubbles were very few on both test. Anyone have any ideas or suggestions? Can the air bubbles be caused by anything other than a leak?

Is there another way to perform an injector cut out test without having the software or do I need the computer to do it?

Thanks for any and all help.

[Rawze]

CM570/870/871 ...
If the overhead valves were out of adjustment, you can get some false positives.

[BC77]

Thanks for the info, what program do you recommend for doing an injector cut out test?

[Rawze]

(02-19-2024 )BC77 Wrote:  Thanks for the info, what program do you recommend for doing an injector cut out test?

http://rawze.com/forums/showthread.php?t...8#pid67948

[CM87183]

(02-16-2024 )Rawze Wrote:  CM570/870/871 ...
If the overhead valves were out of adjustment, you can get some false positives.

Hey Rawze, how exactly does out of adjustment valves cause a false positive on an injector leak test. I've been chasing leaky injectors and I'm trying to figure out if I'm getting bad reman injectors or if there's something else going on.
Thanks

[tree98]

On the 871 the injectors are cam operated. As things wear, the injector can be held open to long and combustion gases get pushed up into the injector as the piston is coming up. That's what the air bubble is.

[marek4792]

Also when you're checking the injector preload, make sure you're using a dial or needle style torque wrench and not the clicky type.. Torque to spec back off and repeat 3 times and while holding the preload tighten the jam nut and torque it to spec. Very common mistake that results in headaches because you/mechanic aren't using the right tools.

[Rawze]

(09-14-2024 )CM87183 Wrote:  

(02-16-2024 )Rawze Wrote:  CM570/870/871 ...
If the overhead valves were out of adjustment, you can get some false positives.

Hey Rawze, how exactly does out of adjustment valves cause a false positive on an injector leak test. I've been chasing leaky injectors and I'm trying to figure out if I'm getting bad reman injectors or if there's something else going on.
Thanks

Because if the injector cam rockers are out of adjustment, they do not hold the injectors down in the closed position all the way ... making for a false positive on the test.

[CM87183]

(09-14-2024 )Rawze Wrote:  

(09-14-2024 )CM87183 Wrote:  

(02-16-2024 )Rawze Wrote:  CM570/870/871 ...
If the overhead valves were out of adjustment, you can get some false positives.

Hey Rawze, how exactly does out of adjustment valves cause a false positive on an injector leak test. I've been chasing leaky injectors and I'm trying to figure out if I'm getting bad reman injectors or if there's something else going on.
Thanks

Because if the injector cam rockers are out of adjustment, they do not hold the injectors down in the closed position all the way ... making for a false positive on the test.

Hey Rawze,
I believe I have an injector that is leaking on the front half of my cm871, I get plenty of bubbles when cranking and the timing of it seems to be only one injector, but when I try and bar the engine over I can't get it to bubble. I've tried adding a smaller hose to try and make it bubble easier, but I just can't seem to get it to bubble while barring to verify what cylinder it is. Is there anything else I can try to identify what cylinder is leaking?