[jrd22]

Diesel engines have either a manual fuel shut off/on like yours, or an electrically operated fuel solenoid valve. The manual valve requires no electricity and is therefore more reliable and simpler. With a solenoid valve you only need to turn the key off to stop the engine. Most newer diesels use a solenoid which is a mistake IMHO for marine use. I have a Yanmar with manual shut off and we have always turned the key off first and then pull the fuel shut off to stop the engine. I don't think it could have damaged anything by turning the key off and then on again while the engine was running, we have done it several times by mistake, but I am not familiar with your system. A Volvo dealer could give you better info. on that.