Symptoms and Causes of Common Rail Injector Failure

smoking truckTwo of the most common questions we get from customers are “Why did my injectors fail?” and “What can I do to avoid it?”

In over 40 years of diesel combustion research, Baileys has seen, repaired and prevented just about every cause of injector failure, and in this post we have compiled some of the most common symptoms, causes and ways to prevent the premature replacement of your common rail injectors. While most of this post directly addresses the injectors BDG manufactures and sells, the info will be relevant to all common rail diesel vehicles.

Why does my Hilux (Prado) blow white smoke and cold start rattle?

Chances are the problem is internal injector leakage caused by seal failure. As this seems to be a common problem on our Facebook page and the forums, and the dealers all seem to be explaining it away, I took a quote from Matt Bailey at BDG:

“The sealing washer that goes around the nozzle starts leaking oil into the cylinder overnight. Worse however is when the combustion gases, particularly carbon, leak past, ending up in the oil, blocking the oil pick-up in the sump and starving the engine. CATASTROPHE.”

A simple check for this is to leave the nose of the car pointed down overnight. If the symptoms are worse, the sealing washers are faulty.

Remember that common rail systems run at enormous pressure, so avoid tuning that increases pressure in the rails.

Why does my Hilux (Prado) rattle at low RPMs ?

Under light loads (+/- 2000 RPM) these engines go into a high advance, so some engine rattle is normal. If you do notice it getting worse, we suggest you first pull the filter for inspection. If it is full of “black stuff”, replace it. **We know Toyota has stated that the filter does not need changing.. Our experience is different.

Another common cause of Hilux low RPM rattle is a dirty or clogged intake manifold. It is worth trying (and good maintenance practice) to remove and clean the intake. The EGR system feeds exhaust gasses back into the intake, including carbon, which builds up over time. We regularly see cars with 35-50% of the inlet blocked up where the EGR links in. Once we have cleaned this out, the rattle has seemed quieter. Either way, this is good maintenance practice, as it balances out the AFRs (air-fuel ratios), giving some fuel economy gains.

What causes my Hilux (Prado) injectors to fail?

We all know that these common rail injectors are likely to fail at around 120-140,000  km’s. Symptoms of a failing injector are a loud knock that is audible with the windows down. You hear this sound best when the vehicle is cold, or when sound bounces back to you from another car or wall. It is loud and nasty, and usually goes hand-in-hand with poor fuel economy and sometimes a rough idle. We have seen injectors start to fail as soon as 75,000, and last as long as 250,000 + km – so what makes the difference?

Wear and tear – These common rail injection systems operate with 30-100% more pressure than previous systems. This has a definite impact on injector longevity. Next, these injectors fire four to five times per combustion stroke, instead of just one. That is a lot of additional work. Lastly, they have a much smaller operational tolerance than previous injectors. It is a miracle they last as long as they do!

Fuel factors – We all know that foreign matter in the fuel is no friend. The physical tolerances within these injectors is as little as 1 micron. Therefore, for obvious reasons, we recommend fitting the smallest micron filter available.

Fuel in Australia contains chemicals that will corrode the injector body, leading to problems. The best way to avoid this is to not let the fuel “sit” – Drive your beast regularly!

Other than taking these precautions, the only real fix, once the problems have set in, is to replace the injectors.


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