Diagnostic Methods for Diesel Engine Injectors Part 2

Next, we will continue to introduce the diagnostic methods for diesel engine injectors.

Crank time

The normal start-up time of a common rail injection system is usually about three to five seconds. This is the time required for the common rail pump to establish fuel pressure to the "threshold". The threshold for starting is when the fuel distribution pipe pressure reaches approximately 5000 pounds per square inch. A normal common rail system will operate at a pressure of 5000 pounds per square inch at idle and can reach 30000 pounds per square inch at full throttle.

In Cummins engines, the controller will not activate the fuel injectors until the fuel distribution pipe pressure reaches the threshold. Therefore, when the fuel injector ruptures and fuel leaks downwards in the injection system, in order to refill the fuel system and reach the threshold required for ignition, the starting time will almost double.

Accurately determining which fuel injector is broken can be a lengthy process.

Cummins suggests starting a simple visual test. First, remove the valve cover, then turn the engine to idle. Study the fuel injector body of each cylinder using a lamp. Sometimes, if the outside of the fuel injector body cracks, you may notice a small wisp of smoke coming out of the injector.

The smoke that can sometimes be seen is actually atomization released by fuel from cracks. But this strand should not be confused with gas channeling, as gas channeling can also be seen. If the fuel injector ruptures externally and produces a wisp of smoke, you will be able to smell the smell of diesel in the air.

This type of diagnosis is very useful when trying to identify which fuel injector may have external cracks. If you are still unsure which one caused the problem? Then you must dig deeper and isolate each cylinder. The only way to isolate a single cylinder is to cut off the fuel supply - in order to achieve this in a common rail system, you must turn it off.

For Cummins engines, start from the first cylinder and remove the hard wire between the fuel distribution pipe and the fuel injector.

Next, place the cover on the fuel distribution pipe where the fuel line is located.

(Warning: This "bottle cap" is a special tool specially made by Cummins for this test. This type of cap can withstand high pressure related to the common rail system. Do not use anything else, otherwise you may be injured or die from high-pressure fuel.)

Next, start the engine and see if the starting time is shortened. If not, proceed to the next cylinder until it can be determined which cylinder caused the long crank time.

If the Cummins engine does not run at all, the fuel injectors will usually crack severely, so that the fuel system will never reach the threshold. This type of oil can also be severely diluted by diesel fuel. By installing a cover on each cylinder at a time, you can isolate the faulty fuel injector - when the engine fires quickly and normally, you will know that you have found it.

Power loss during power stroke

Although today's diagnostic tools and advanced engine electronics make it easier to identify performance issues with diesel engines, this does not mean that all problems can be solved so easily. For more details, please feel free to contact Dingbo Electric.

As a professional diesel generator manufacturer, we always insist on using first-class talents to build a first-class enterprise, create first-class products, create first-class services, and strive to build a first-class domestic enterprise. If you would like to get more information welcome to contact us via sales@dieselgeneratortech.com.