Clinton Brett has over 30 years’ experience as a specialist in diesel fuel injection. With a passion for educating technicians on diesel systems and fault diagnosis, he founded Diesel Help Australia.
In an effort to address frequent questions from diesel vehicle owners, Clinton has created an informative and comprehensive guide filled with best practice.
Diesel Help Australia works directly with the automotive industry. If you're not from the automotive industry, and are having issues with your diesel, we can refer you to skilled Diesel Help members in your area. Or, if you from the automotive industry and require diagnostic support? Diesel Help members please Log A Job, for non-members consider joining Diesel Help.
Owning a diesel vehicle can be a game-changer, offering power, efficiency, and reliability that are hard to beat.
Whether you're a seasoned diesel enthusiast or thinking about switching from petrol, this guide will help you answer common questions about owning a diesel-powered vehicle.
We will start with an overview of Common Diesel Faults and Repairs, and you'll find in bold links to the relevant sections of the guide.
COMMON FAULTS & REPAIRS
When you search for a fault code or symptom related to a common problem with your vehicle on Google, you're likely to find numerous answers—sometimes a hundred or more! So how do you figure out if it is a common fault?
Creating a diesel-only technical bulletin library took over 10 years. However, it took over 30 years of diesel experience to decide what was a common fault and what was human intervention. Our expanding technical bulletins for mechanics have common faults and repairs ranging from specific manufacturer flaws to earlier work conducted by owners and qualified mechanics. This includes but is not limited to service, maintenance, adjustments, upgrades, modifications, or misdiagnosis involving replacing a part.
FUEL SYSTEM
Common faults within the fuel system are often caused by fuel quality. The reason is because all diesel fuel systems, common rail and non-common rail, are completely dependent on diesel fuel to hydraulically operate and lubricate the components.
Be mindful of your refuelling point. For example, if you're refuelling from a farm bowser, when was the last time the tank was cleaned or fuel checked? Avoid cheap offerings of fuel, stick with the main brand suppliers and avoid recently flood-affected stations.
Many people believe diesels are more fuel efficient than petrol, but is this true?
​INJECTORS
A commonly replaced component in the fuel system is the injector. Often, the failure has been caused by contaminated fuel.
The injectors are part of the same fuel circuit, which includes a fuel pump, rail, and pipes -the image below demonstrates the diesel fuel path in red. In instances where contamination leads to injector failure, it is crucial to replace the entire fuel system. Otherwise, installing new injectors may result in the same failure occurring again.
When an injector fails as a result of normal wear and tear, with no signs of contamination, then it is acceptable to replace a full set of injectors. Based on my experience, if the system has done more than 200,000 kilometres, issues can arise afterwards due to the vital matching of the operating system.
Contamination includes petrol, so what should you do if you put petrol in your diesel?
INJECTOR SEALING WASHERS
These provide a secure compression seal between the injector and the seat; it is not uncommon for these fail.
If compression is lost in a diesel engine, severe consequences will arise. A compression loss will affect the overall performance and eventually fail an engine.
​SUCTION CONTROL VALVE
Unfortunately due the the location of the suction control valves, they have been a common failure. They are part of the high pressure pump and the first valve immediately after the fuel filter.Â
In vehicles that are poorly serviced or have insufficient filtration, the ultra-fine media paper in the filters can become lodged in the valve. This can lead to it sticking, triggering a fault code, or even causing a loss of power and stalling.
​EXHAUST GAS RECIRCULATION VALVES
The Exhaust Gas Recirculation, usually referred to as EGR. This is the system responsible for reducing harmful emissions.
EGR valves and EGR coolers experience extremely high temperatures whilst removing those emissions from the exhaust. This process causes carbon build up, causing the EGR valves to stick. If the vehicle is not serviced correctly, these valves may prematurely fail.
Another aspect to consider about the emission system is vehicles equipped with a Diesel Particulate Filter (DPF). When a DPF fault code is present in the engine’s computer or a light illuminates, it does not necessarily mean the DPF is blocked or requires replacement. We have some helpful tips for maintaining your DPF.
EGR COOLERS
EGR coolers are prone to leaking internally. Due to the corrosiveness of the harmful gases recirculated, the cooler can fatigue and begin to leak engine coolant into the system.
Due to the coolant loss, a blown head gasket is inevitable if not rectified early.
It is recommended to regularly monitor your coolant tank levels. Place a texta mark at the upper level when the engine is cold and use this same mark to check the levels at the same temperature.
TURBO CHARGER
Turbochargers rotate at a high speed, much higher than that of the engine.
We frequently encounter turbo failures in vehicles with poor maintenance records.
In many cases, it has failed early due to driving habits. A turbo requires constant lubrication, particularly because of its high rotational speeds of around 50,000 revolutions per minute (rpm), while the engine would only be working between 800 and 5000 rpm.
The turbo is dependent on lubrication from the engine oil, and the oil pump, which is driven by the engine, is designed to continuously pump oil throughout the engine. The failure of the turbo is caused by the bearings due to a lack of lubrication. The degradation takes place after the engine is switched off, especially if this occurs soon after the engine has been driving at high speeds.
Once the engine shuts off, the turbo remains spinning at around 60,000 rpm, and unfortunately, with the engine switched off by now, there is insufficient oil delivered to the turbo bearings, which take longer to slow down, even more so if no oil is present to create friction. This is why the operator needs to allow the engine to idle for around 30 seconds to 1 minute before shutting the engine off.
A common accessory for diesels with a turbo charger is a catch can. Before considering this option, please read what our diesel specialist thinks about Catch Cans.
ENGINE FAILURES
Modifications play a key role in engine failures. Many owners of the modern common rail diesel have never owned a diesel and automatically feel the vehicle does not perform like their previous petrol car. That’s because a diesel suits an entirely different purpose: moving heavy loads with less fuel to do this, not running a ¼-mile drag race.
Other than remapping, fitting a larger exhaust to a diesel has become a novelty, particularly for those who believe it sounds cool and feels like it is performing better. Unfortunately, if not done right, it has become an all-too-common failure. Find out if it’s ok to make your diesel go faster.
Running a larger diameter exhaust may reduce exhaust temperatures, but for a diesel to perform as intended, reducing combustion temperatures can have an adverse effect on the long-term reliability of the diesel engine.
So, with all these considerations, is it cheaper to service a diesel-powered vehicle?
Happy diesel driving!
Clinton Brett originally created this article for AutoGuru:Â What Are The Most Common Diesel Engine Repairs?Â
