Because they're especially sensitive to water in the fuel, diesel engines have a special kind of filter called a water separator. Even a tiny amount of water can wreak havoc on a diesel engine. It can destroy fuel injector nozzles, crack cylinder liners, or cause premature valve wear among other problems. Water in the combustion chamber usually causes stalling of the engine. Water separators have two parts. One part is a removable filter that traps dirt from the fuel, and the second part collects moisture for removal. Both components should be cleaned or drained often. Contact a qualified diesel mechanic or auto parts store for more information on fuel filters and water separators for diesel engines.