The system will need to be depressurized before connecting to the injector cleaner, which actually comes in two different types of packaging. Part #1120 is self-pressurized with a threaded valve that requires a special adapter to pierce, while part 1126 is a pourable product that requires a canister and air compressor. Either way, the product is fed through the fuel rail and the vehicle runs directly off the injector cleaner until fully consumed. This usually between 15 and 30 minutes depending mostly on engine size.