Electronic Diesel Injection System 174-7526

A: It must be done on an injector test bench. Main inspection items: 1. Opening pressure: Adjust the pressure regulating screw to allow the injector to start injecting fuel at the standard pressure. 2. Sealing: Increase the pressure to slightly below the opening pressure and maintain it, observing the pressure drop rate to judge the sealing performance of the needle valve assembly. 3. Atomization quality: Press fuel at a certain frequency; the fuel jet should be uniform, fine, and mist-like, without dripping or deflection. 4. Fuel cut-off crispness: There should be a crisp "plop" sound at the end of injection, with no after-drip phenomenon.

A: The effects are significant. Excessive opening pressure: This leads to delayed injection; although atomization may be good, the high-pressure fuel pump is overloaded, potentially causing insufficient injection duration, reduced engine power, and black smoke. Low opening pressure: This leads to premature fuel injection, poor atomization, incomplete fuel combustion, rough engine operation, knocking, reduced power, increased fuel consumption, severe black smoke, and may even cause piston burning due to fuel dripping.

A: Needle valve assembly wear is the most common fault. Symptoms: 1. Fuel injector dripping, leading to afterburning, increased exhaust temperature, and backfiring/sparking from the exhaust pipe. 2. Poor fuel atomization, resulting in a thin, thread-like fuel jet. 3. Pressure cannot be maintained during sealing tests. Usually, it is not necessary to replace the entire injector assembly. The injector assembly can be replaced individually (needle valve and valve body must be replaced as a pair), and then the opening pressure can be readjusted on a test bench. This is the standard repair procedure. The entire assembly only needs to be replaced if components such as the housing or spring seat are damaged.