TECHNICAL DISCUSSION

A LOOK AT COMMON RAIL DIESEL INJECTION

The common rail injection system helped to revolutionize the light duty diesel market and not only brought about better emissions control (OEM’S main goal) but also led to quieter running engines due to higher injection pressures—and, of course, better all-around performance. The common rail injector is a pretty impressive little piece, with so many small moving parts that help maximize efficiency and atomization in the cylinders under each combustion cycle.

In the 2003 model year Dodge converted to the common rail platform and said goodbye to the VP-44 injection pump. At the time, the 12-valve Cummins and P7100 injection pump was king of the horsepower wars and no one really believed in the potential of the common rail platform. But as time went on, a small few started pushing the limits of the system—changes in injection nozzles, modified CP3 injection pumps and even dual CP3 pump kits became available. As performance tuning started to improve, the common rail Cummins really started gaining in popularity as both a cleanerburning tow rig and a full-blown competition hot rod.

In the beginning, common rail injectors were needed to produce 300-350 hp to meet the OEM needs for new light duty diesel trucks, and whether or not they knew there was more potential in the injector that’s kind of where they limited them. Lucky for us the aftermarket has been able to capitalize on the new CP3 and common rail technology and through the years has engineered and developed injectors capable of 2,000+ horsepower today.

Coy Larsen, the injector specialist at Industrial Injection, who has likely rebuilt more common rail injectors than anyone in the country, offered a little insight on what he deals with on a day-today basis. Larsen has a deep knowledge of the internal workings of the common rail injector and could probably assemble one with his eyes closed. While in the shop with him we wanted to know what he sees fail most often, what goes into rebuilding an injector and what improvements can be made to the factory unit.

Most of the failures seen from the Cummins common rail platform comes from fuel contamination and lack of overall vehicle maintenance. The factory injector has a great design, but due to extremely tight tolerances and the 20,000+ fuel pressure going through them even the smallest particle of contamination can cause internal corrosion and failure in no time. Erosion of the ball seat inside the injector causes fuel to leak past it when closed, which causes a rough running condition or even a nostart situation. Water and other contaminants in the fuel can lead

Notice the rust spots developing around the armature plate. This kind of wear would lead us to believe that poor maintenance, water in the fuel or another form of fuel contamination and overall vehicle neglect has caused this injector to fail. This is a core that will not likely be saved.