When replacing an injector in a Cummins ISB-style common-rail school bus engine in-chassis, the technician should:

1. Reuse the old injector hold-down and copper sealing washer
2. Tighten the high-pressure line as tight as possible
3. Skip cleaning the injector bore
4. Install a new injector sealing washer/o-rings and torque the hold-down to specification, then perform any required injector trim/coding