(1) Directly replace Cummins 3164001. Includes 3164002-Test adapter plate / NPN O-ring / 3164009-Hose Fitting / 3163527-Flexible Tubing. Works on all Cummins ISX and Cummins Signature Engine. Checking for combustion gas leaks back through the injector rail check valve or other conditions that will allow gas leakage through the injector into the fuel rail.