If proper maintenance is performed and problematic practices can be avoided, most diesel owners will go trouble-free

If you’re a diesel owner with an older engine (pre-common-rail), besides the general maintenance advice, like changing your fuel filter regularly, this article doesn’t apply to you. This is because older diesel injection systems only use much less fuel pressure modern engines, and older injectors send the fuel through much larger passages.
Why is there such a difference with common-rail injectors? Modern common-rail diesel injectors can fire up eight times per engine cycle depending on the maker. This increases the wear on the injector compared to the older diesels vehicles. Diesel injectors fail mainly because it has to do with the quality of the fuel running through the injector and DENSO says based on its experience, there’s always room for improvement in our fuel quality.
According to DENSO one of the main failures is high internal leakage or return flow. The indicators for this are an engine becoming hard to start or a ‘low common-rail pressure’ error code is displayed when the engine is scanned.

Common causes are:
• Worn injector ball seat;
• Blown internal high-pressure seal;
• Incorrect nozzle needle clearance;
• Cracked nozzle body; and
• Cracked injector body.

The prevention is to keep fuel system clean, change fuel filters, purchase fuel from reliable sources, and avoid filling from portable fuel tanks. Also, avoid aggressive tuning that increases rail-pressure and injector pulse widths and do not remove pressure-limiting devices from the system (they are there for a reason). Do not use counterfeit injection components that are not properly designed or manufactured.

For more information see the DENSO feature in the September edition of Australian Automotive Aftermarket Magazine or visit