Testing and Overhauling Fuel Injection Valves
If you are new to the world of marine diesel engines, you need to brush up on a number of different things—testing and overhauling fuel injection valves being among the top most important ones.
In this article, leading ship main engine parts supplier, Changrun Trade sheds light on the best practices to assess fuel injector valves and repairing them where necessary.
Checking Fuel Valves
All fuel valves extracted from the engine must be inspected. Even in cases where a ship is halted on heavy fuel oil, for example in ports, injectors should be quickly extracted and tested with diesel oil before their temperature drops.
This helps ensure proper cleaning of the components. Remember that if fuel valves are left to get cold before being checked, they will give poor performance results even if they are in the perfect condition.
Typically, fuel valves have the right spray profile but open up at lesser pressure. You can adjust pressure without actually opening up the valve. In addition to this, majority of manufacturers also recommend avoiding opening the injector valves unless there is a significant issue like fuel dripping or choking.
Simply put, the valve should be cleaned, adjusted and inspected only on the outside.
In cases where the fuel valve is not performing right and has some problems, it needs to be extracted and repaired. To make sure that you extract and disassemble it appropriately, always refer to the manual. Here is a quick breakdown of what you will most probably have to do:
• The needle guide should be submerged in fresh diesel oil and the needle be inspected for free movement. If you notice that there is any resistance in the movement, consider dipping and checking the needle repeatedly. The friction is typically due to sludge or carbon.
• Once the needle has been successfully cleaned, it should be extracted and allowed to free fall in the oil. A smooth movement as the clearance makes the way for the oil to come out means that the needle guide is in the right condition.
• If the needle fails to go down it should be cleaned again. If there is no improvement the needle must be bent. Inspect the needle for signs of overheating.
• Inspect the nozzle spring for poor seating or breakage.
• Inspect the leak off pipes, packing and other components. If the engine is water cooled, the cooling pockets should be blasted with compressed air.
All the holes in the injector should be firing. You can check them by using a cone shaped filter paper or through a torch light. In case of the filter paper, the number of holes on the paper will indicate the number of holes firing. As this is a high pressure procedure, make sure you practice appropriate safety measures.
If your fuel injector valves have worn out or are not functioning right, make sure you replace them with reliable ones immediately. Choose only a renowned marine spares supplier like Changrun Trade.