0414720359 Unit Injector – Product Page

Every time a cylinder fires, it delivers a pulse of torque to the crankshaft. In a well‑balanced engine, these pulses are evenly spaced and uniform in strength, resulting in smooth rotation. However, when injectors have differing flow characteristics, the torque pulses vary – some cylinders contribute more, some less. The engine still runs, but the rotation is not perfectly smooth. This variation is felt as vibration, heard as uneven engine note, and measured as crankshaft speed fluctuation. The 0414720359 is manufactured with matched fuel delivery across cylinders, ensuring that each injector delivers the same fuel quantity for a given energising time. This reduces the torque spread between cylinders, resulting in smoother engine rotation, less vibration, and a more refined driving experience.

The 0414720359 is designed for VAG PD engines where smoothness is a priority:

Volkswagen 1.9 TDI – BKC, BLS, BXE, BJB, BSW codes in passenger cars and light commercial vehicles.

Audi 2.0 TDI – BKD, BMN, and BRE codes in passenger cars.

Seat and Škoda TDI – sharing the same PD engine architecture.

The injector uses a threaded mounting with a copper sealing washer at the nozzle end and an O‑ring on the upper body.

To achieve the intended smoothness:

Clean injector bores – Carbon buildup in the bores can affect injector seating and heat transfer, causing uneven performance.

Copper washer – Always use a new copper washer. A leaking washer allows combustion gas to affect the injector, altering its flow characteristic.

Torque sequence – Tighten the injector hold‑down clamp to 20 Nm, then loosen, retighten to 7 Nm, then turn 1/4 turn. This ensures consistent seating across all cylinders.

Return hoses – Ensure the return hoses are clear and not pinched. A blocked hose can create backpressure, altering the spill timing.

ECU adaptation reset – After installation, perform a fuel system adaptation reset. This allows the ECU to learn the new injector characteristics.

Drive cycle – After adaptation, drive the vehicle for 20–30 km to allow the ECU to fully learn the injector's characteristics.

The 0414720359 is compatible with EN 590 diesel and B7/B10 blends. Fuel quality affects torque spread through:

Viscosity – Higher viscosity (cold fuel or biodiesel) can increase the injection duration slightly, but the effect is uniform across all cylinders.

Lubricity – Low‑lubricity fuel can cause uneven plunger wear, increasing torque spread over time.

Water – Water above 0.2% can cause corrosion, affecting injectors unevenly.

To maintain smoothness, use fuel that meets EN 590 standards and change the fuel filter regularly.

Under normal conditions, the 0414720359 provides 200,000–250,000 km of service. The smoothness degrades gradually as the injectors wear:

Plunger wear – increases leakage, reducing fuel delivery for that cylinder.

Nozzle erosion – increases flow, increasing fuel delivery for that cylinder.

Solenoid wear – changes the timing, affecting combustion quality.

The first sign of smoothness degradation is often a subtle vibration at idle or a slight roughness during light acceleration. When the vibration becomes noticeable, the injectors are approaching the end of their service life.

Q1: The engine vibrates at idle but smooths out when revved – could the injectors be the cause?

Yes. At idle, the injection quantity is small, and any flow variation between injectors has a larger relative effect, causing vibration. At higher RPM, the injection quantity is larger, and the relative variation is smaller, so the vibration diminishes. The 0414720359's matched flow reduces this vibration.

Q2: Can I check the torque spread without specialised equipment?

You can check the cylinder balance values using a diagnostic tool. If the values are within ±2%, the torque spread is good. If one cylinder is consistently above +3%, that injector may be causing the vibration.

Q3: The car has a slight vibration at 80 km/h – is this injector‑related?

A vibration at a specific road speed is usually tyre‑ or driveline‑related. Injector‑related vibration is speed‑related (engine RPM), not road speed‑related. However, a rough engine can feel like a driveline vibration – check the RPM at which the vibration occurs.

Q4: Does the 0414720359 improve fuel economy by reducing torque spread?

Indirectly, yes. By reducing torque spread, the ECU does not need to over‑fuel some cylinders to compensate, which improves efficiency. The improvement is typically 2–3%, depending on the engine.

Q5: The engine has a harsh note at idle – could the injectors be the cause?

Yes. Harsh combustion noise is often caused by uneven injection timing or quantity. The 0414720359's matched characteristics reduce this. However, harsh engine note can also be caused by a worn timing chain or a failing alternator bearing – check these first.

Q6: Can I use the 0414720359 to reduce the vibration of a high‑mileage engine?

Replacing worn injectors with the 0414720359 can restore the original smoothness. However, if the engine mounts are worn, the vibration may persist. Check the engine mounts before blaming the injectors.

 

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