Fuel is a valuable asset; treat it that way

Dec 5, 2016 by Capt. Jeff Werner

High-pressure common rail (HPCR) engines are now the norm for all new diesel engines that are installed aboard yachts. The need for HPCR engines has been driven by strict emission guidelines in the maritime industry. At the heart of HPCR engines are common rail diesel injectors, which are designed to operate at 30,000 psi and above. To put this into perspective, conventional diesel injectors operate at about 3,000 psi. An HPCR injector delivers fuel to the cylinder under the guidance of an electronic control unit that sends electricity to the injector solenoid. The energized solenoid activates a plunger that lifts a ball valve clear of its seat. This allows a small amount of fuel to flow through the injector, which raises the injector needle so the fuel can spray through the nozzle into the cylinder. Due to diesel contamination, both the valve assembly and the injector nozzle can become failure points. Fuel contamination can cause erosion of the ball valve and its seat, and the spray holes in the injector nozzle can be blocked or eroded. Injector nozzle hole blockage and erosion leads to poor fuel atomization or lack of atomization that causes partial function failure. This partial failure corresponds to inefficient engine performance. Signs of partial functional failure include reduced engine power, reduced engine RPM, increased fuel consumption, smoke, noise, poor idle, and rough starting. Valve and valve seat erosion can lead to dripping fuel injectors, which can trigger a multitude of problems and eventually full function catastrophic failure. The predominant failure occurring from dripping fuel injectors is excessive piston crown temperature, which can cause the crown to deform or melt, and the engine stops. Catastrophic failure is expensive to repair, let alone adding up the yacht’s needed downtime to remedy the engine that ceased to function. Many HPCR engine failures are misdiagnosed at first, but after further analysis they are correctly attributed to the effects of poor quality fuel on the fuel injection system. High-velocity and high-pressure fuel flow, with even the smallest amount of contamination, will gradually erode the sealing surfaces of the injector valve seat and nozzle. Once valve wear has been initiated, a failure chain reaction gradually occurs, resulting first in a partial functional failure, and evolving into the full functional failure of the valve. The HPCR injector failure chain reaction is a cascade of many events:
  1. Valve erosion begins.
  2. Fuel leakage through the valve mating surfaces initiated.
  3. Localized hot spot generation through the seepage zone.
  4. Reduced fuel pressure at the nozzle.
  5. Computer controlled engine management system compensates for reduced fuel volume by increasing the length of the injection cycle, which sprays more fuel.
  6. Injector nozzle hole deformities and blockage results in reduced fuel atomization.
  7. Soot builds up within the cylinder.
  8. Increased emissions from the engine.
  9. Loss of power.
  10. Partial functional failure point.
  11. Fuel leakage rates increase as wear continues.
  12. Fuel consumption increases as the Engine Controller Unit (ECU) tries to compensate for leakage.
  13. Visible and audible signs of failure.
  14. Full functional failure point, and engine stops.
Poor quality or contaminated diesel fuel contributes to more than 80 percent of fuel system-related failures in HPCR systems. To overcome the challenges of maintaining a reliable fuel system, a paradigm shift must be made in the way yacht owners view diesel fuel and its function within the engine. With the introduction aboard yachts of new diesel engines equipped with advanced, high pressure common rail fuel injection systems, many yacht owners are experiencing a high frequency of failure, decreased system reliability, and the cost challenges from a technology that promised to improve environmental impact and operational efficiency. It is imperative that yacht owners dramatically alter the way in which they view and treat the fuel their yachts consume. Instead of simply seeing fuel as a necessary expense, it should be viewed as a “critical reliability component” of the fuel system, and treated as a valuable asset. Capt. Jeff Werner has been in yachting for almost 25 years, and is the owner of Diesel Doctor (MyDieselDoctor.com). All Triton readers receive a 10 percent discount on online orders. Comments are welcome at editor@the-triton.com. Topics: