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Why Change Diesel Injectors:
Its a common question; why change diesel injectors and how to tell when mine are worn?
So we got about answering it:
Difference in Work Load:
One of the most surprising things about common rail injectors is the work load that they are subjected to. The older injection systems operate around 1000 bar and inject once per combustion event. Modern Diesel Injection systems inject up to 5 times per combustion stroke and with anything up to 2200 bar!
Tolerances in these injectors:
The main way these injectors are able to deal with such massive work loads by they employing SUPER FINE Tolerances in order to promote best possible performance.
The Bits that fail inside the injector:
Unlike many years ago where a nozzle would simply wear out, metallurgical advancements have moved to such a point where the nozzles are now not really the issue. Whilst they do ‘wear’, its nothing like it used to be despite the much higher work loads.
So what does fail?
The most common failures we see here are Control piston and nozzle needle failures. These are the moving parts that dictate when and how the injector opens and starts injecting. The wear that we see is nearly always seizure related failures which can be due to excessive clearances (ie it worn out). However, its usually accelerated by either a lack of lubrication or physical particles coming through the fuel.
So lets take a look
Lack of Lubrication:
BDG recommends the use of BP ultimate fuel. Its not just something we say but actually something we do as all our company vehicles have a BP fuel card. We suggest this as BP Ultimate is the only fuel guaranteed to meet Euro grade diesel standards including Cetane rating, lubricity and so on.
Another potential cause of the lack of lubrication can also be water getting through the trap and into the fuel system. Water has no lubrication and under extreme injection pressures does some pretty crazy things. This leads to a highly likely scenario where scoring occurs in moving parts inside the injector. Like a seized liner and piston, once it starts its only going to spread.
The water in the fuel also causes something else which I feel is the bigger issue – RUST.
Physical particles in the fuel:
This is probably the bigger concern for common rail injection systems.
I actually believe there to be 2 main contributing factors, Rust and ‘Rubbish in the fuel’.
The rust can develop in the fuel rail or certain parts of the injector. After a while it will continue to grow and start to break off sections, which being after all of the filters, will go straight through the fuel system.
So How can you tell?
Why change diesel injectors? You’d want to see one of these issues:
- Engine ‘Rattles and knocks’
- One of the easiest tells is when the engine starts to rattle and knock. Whilst some engines are ‘naturally noisy’, its pretty clear to tell when one cylinder doesn’t match the rest.
- These noises come from a cylinder to cylinder imbalance (or shot to shot imbalance) which highlight the injector is no longer functioning correctly.
- *there are other potential reasons for engine noises, such as SCVs (click here for more information), engine issues, sensor issues and so on. Always best to get a GOOD Diesel mechanic to investigate.
- Engine ‘vibration’:
- Clients usually comment after having their injectors replaced ‘The engine is so smooth now”. This is usually due to variations in shot to shot consistency. The ECU can’t learn and therefore cannot ‘cover up’ these issues
- Another great indication that something isn’t quite right is the presence of smoke from the exhaust. Smoke caused from diesel injectors is usually due to incorrect flow rates. Smoke is usually caused from wear or control issues with the injectors.
- *Diesel Smoke can be caused by MANY other factors that can cause smoke in diesel engines.
- Fuel Economy:
- This isn’t always the best indication as sometimes as nozzles wear and flow more, it can actually give better fuel economy!
- Injector Feedback Values:
- The ECU of the vehicle has the potential to learn and adjust (usually at idle) that helps ‘cover up’ any potential issues keeping them somewhat at bay. These ‘learnt values’ or ‘adjustments’ are visible via a trade level scan tool, and thus are accessible for reading.
- For example, see our blog post on diagnosing 1kd by clicking here
- So you’re usually able to tell when an issue is occurring via a scan tool long before the driver can actually tell something is wrong. For this reason we always recommend the use of a QUALITY DIESEL MECHANIC, not just someone who ‘also works on diesel’.
- To see who we recommend around Australia, check this link here.
So; Why Change Diesel Injectors?
Why change Diesel Injectors? There’s really only 2 reasons:
- To Fix a problem
- Replace the injectors with a more ‘robust’ injector.