Because the entire system is mechanical, diagnosing a bad injector relies on a combination of sound, feel, and performance. Common symptoms include:
Rough Running & Misfiring: A faulty injector may not deliver fuel correctly, causing a noticeable miss or vibration, especially at idle.
Excessive Black Smoke: A leaking or sticking injector can dump too much fuel into a cylinder, leading to incomplete combustion and thick black smoke from the exhaust.
Knocking Noise: A specific "knock" or "tick" coming from a particular cylinder can indicate an injector with a worn plunger or a problem with the injector's adjustment.
Hard Starting: If multiple injectors are leaking, they can fill the cylinders with fuel, making the engine extremely hard to start and potentially leading to hydraulic lock.
Power Loss: A simple lack of power across the RPM range can often be traced back to injectors that aren't delivering their rated amount of fuel.