Injector leak test

[Rawze]

The injector leak test kit you have listed there is only for the older Dual-Over-Head-Cam (DOHC) CM570, CM870, and CM871 ISX engines. It will not do squat for test on a common rail CM2250, CM2350, etc. engines.

BTW: none of those engines should drop more than 4,000 psi in one minute.

To find the issues...

FIRST, start by replacing the high pressure relief valve at the front end of the main fuel rail if it is more then 250k miles old. use the Quickserv procedures to see if it is leaky otherwise.

NEXT, re-torque all the Quell tubes to cumins spec that feed the injectors and do the leak-down tests again. For all you know it could just be something simple, and not an injector intself.

If it still fails leak down tests, then start by capping off injectors, front 3, do tests again ... then back 3 ... and isolating what injector(s) that is causing the issues that way. Cummins makes fuel line caps for this test on the common rail engines.

If you find that it is more than 2 injectors are leaking like that, it is highly likely that some damage to them has occurred at some point. A 6-pack is not out of the question at that point. If, say, only one or 2 is leaky, replace only them.