The injection system is designed to inject the right amount into the engine's combustion chamber, at the right timing.Checked 2026-08-16
Fuel injector
An electronically controlled valve that meters fuel into the intake port or combustion chamber.
Also called: injector · fuel injection nozzle · common-rail injector
What it means
Definition
A fuel injector opens for a commanded time to deliver a measured amount of fuel. Port injection sprays into the intake port; direct injection sprays into the combustion chamber. Diesel common-rail systems also inject into the chamber but operate with their own much higher-pressure hardware and control strategy.
Why a buyer cares
What it changes
‘Injector’ does not identify the injection system or prove the injector caused a mixture or misfire code. Pressure, wiring, deposits and mechanical condition can affect the same cylinder.
In practice
Where you meet it
In engine specifications and on estimates for injector testing, cleaning, sealing or replacement.
Two things that look alike
Not the same as
The fuel pump creates and supplies pressure; the injector meters fuel into the engine.
Read next
Related terms
Fuel pump
The pump that moves fuel from the tank toward the engine at the pressure its injection system requires.
Gasoline direct injection (GDI)
A fuel system that sprays petrol straight into the cylinder instead of into the intake port.
Port fuel injection (PFI)
A fuel system that sprays petrol into the intake port, upstream of the cylinder.
Diagnostic Trouble Code (DTC)
The code an OBD-II system stores to identify which monitored system it found a fault in.
Where this comes from
Sources
The cited DENSO page describes diesel injection; gasoline port and direct injection share the metering function but use different pressures and hardware.