Fuel injector
Definition
A fuel injector is an electrically operated valve that meters fuel into the intake port or directly into the cylinder; the ECU controls quantity by pulse width (opening time). Port injectors run at 3-5 bar, petrol direct injectors at 50-350 bar and diesel common rail injectors at up to 2500 bar, using solenoid or piezo actuators. Diesel injectors wear internally and leak back excessive fuel, which lowers rail pressure and causes long cranking; worn nozzles cause nailing, smoke and uneven cylinder balance. Petrol injectors clog or stick, giving misfires on one cylinder, lean codes and fuel smell from leaking O-rings. Codes: P0200-P0212 (circuits), P0261-P0296 (individual high/low), diesel P1xxx balance codes and misfire P0301-P0312 pointing to the affected cylinder.