Diagnostic apparatus for fuel injector

A diagnostic apparatus for a fuel injector mounted to a fuel injection system which includes:

• a first fuel injector mounted to a first cylinder of an internal combustion engine;
• a second fuel injector mounted to a second cylinder of the engine;
• a third fuel injector mounted to a third cylinder of the engine;
• an accumulator accumulating a fuel for distributing a high-pressure fuel into the first fuel injector, the second fuel injector and the third fuel injector;
• a first fuel passage extending from an outlet of the accumulator to an injection port of the first fuel injector;
• a first fuel pressure sensor disposed in the first fuel pressure passage for detecting a fuel pressure in the first fuel passage;
• a third fuel passage extending from an outlet of the accumulator to an injection port of the third fuel injector;
• and
• a third fuel pressure sensor disposed in the third fuel pressure passage for detecting a fuel pressure in the third fuel passage, and a second fuel passage extending from an outlet of the accumulator to an injection port of the second fuel injector,
• the diagnostic apparatus comprising:
• a self-injection-pressure-return determining portion for determining whether a self-injection-pressure-return occurs in the first fuel passage based on a detection value of the first fuel pressure sensor, when the first fuel injector terminates a fuel injection;
• a pressure-behavior obtaining portion for obtaining a fuel pressure behavior in the first fuel passage and the third fuel passage based on detection values of the first fuel pressure sensor and the third fuel pressure sensor, when the second fuel injector terminates a fuel injection;
• and
• a behavior determining portion for determining whether there is a specified difference between the fuel pressure behavior in the first fuel passage and the fuel pressure behavior in the third fuel passage, wherein
• the diagnosis portion determines that the first fuel injector has a malfunction of continuous injection when the self-injection-pressure-return determining portion determines that no self-injection-pressure-return occurs in the first fuel passage and the behavior determining portion determines that there is said specified difference.

A diagnostic apparatus for a fuel injector mounted to a fuel injection system which includes:

• a first fuel injector mounted to a first cylinder of an internal combustion engine;
• a second fuel injector mounted to a second cylinder of the engine;
• a third fuel injector mounted to a third cylinder of the engine;
• an accumulator accumulating a fuel for distributing a high-pressure fuel into the first fuel injector, the second fuel injector and the third fuel injector;
• a first fuel passage extending from an outlet of the accumulator to an injection port of the first fuel injector;
• a first fuel pressure sensor disposed in the first fuel pressure passage for detecting a fuel pressure in the first fuel passage;
• a third fuel passage extending from an outlet of the accumulator to an injection port of the third fuel injector;
• and
• a third fuel pressure sensor disposed in the third fuel pressure passage for detecting a fuel pressure in the third fuel passage,
• the diagnostic apparatus comprising:
• a self-injection-pressure-return determining portion for determining whether a self-injection-pressure-return occurs in the first fuel passage based on a detection value of the first fuel pressure sensor, when the first fuel injector terminates a fuel injection;
• a pressure-behavior obtaining portion for obtaining, based on detection values of the first fuel pressure sensor and the third fuel pressure sensor, a fuel pressure behavior in the first fuel passage and the third fuel passage when the second fuel injector terminates a fuel injection;
• and
• a behavior determining portion for determining whether there is a specified difference between the fuel pressure behavior in the first fuel passage and the fuel pressure behavior in the third fuel passage, wherein
• the diagnosis portion determines that a leakage malfunction occurs when the self-injection-pressure-return determining portion determines that no self-injection-pressure-return occurs in the first fuel passage and the behavior determining portion determines that there is said specified difference.