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8 Common Diesel Engine Problems with a Quick Fix

There’s nothing worse than when your car or truck starts (or won’t start) making a strange sound. Learn about common diesel engine problems in this post.

In most European countries, and in particular, Portugal, Ireland and Luxembourg, diesel engine cars consistently outsell gasoline cars. And, despite a government drive in the UK to phase out diesel cars, two in five on the UK’s roads are diesel powered. 

In the US, diesel car sales only account for about three percent of all car sales. But, diesel is a more popular choice than gasoline for medium and heavy trucks in the US, where 72 percent of trucks weighing 10,000 lbs and above are diesel-powered. 

Whether you own a diesel car or truck, or you’re considering purchasing a new Kia Ceed Diesel or the Mazda CX-5 2019 Diesel, it’s important to understand some of the issues that diesel engines can have. 

Here are eight common diesel engine problems you might have to deal with. 

1) Hard Starting

Like diesel generators, diesel engines are robust, but they can fail from time to time. One of the most common engine problems is a delayed or difficult start. 

If your diesel engine has a hard time starting up, this is usually due to low compression or an issue with fuel delivery. Because of this, it’s perfectly normal for some diesel engines to crank a little when you start them. 

But, if your engine cranks more than normal, you notice it getting harder to start, or it won’t start at all, you need to get it checked as soon as possible. 

2) Incorrect Weight Viscosity

If you are experiencing hard starting, it can often be the result of engine lubrication with the wrong weight viscosity. 

Diesel lubricants have a much higher viscosity than gasoline. As a result, many people get the viscosity weight wrong when replacing the oil. Another common mistake is to use a single-weight engine oil during warmer weather and forget to switch back to a multi-viscosity oil when the weather cools. 

To avoid issues with the incorrect weight viscosity, the easiest solution is to use a multi-viscosity oil all year round. This way you won’t run the risk of forgetting to switch back, which can end up damaging the engine in the process. 

3) Contaminated Fuel

Since the oil in diesel engines is much more viscose, it’s also much easier for it to get contaminated. The four most common contaminants in diesel engine oil are fuel, soot, water and glycol. 

Since these contaminants can spell disaster for your diesel engine and can be difficult to remedy, it’s crucial to analyze your oil regularly as a way to detect such potential issues early on. 

4) Lack of Power

An additional fuel-related problem with diesel engines is a lack of power. This is most noticeable when your vehicle has trouble starting up or accelerating. 

A quick check of the fuel filters and other simple maintenance tasks you can do yourself can sometimes reveal the cause. Other things to look for are excessive lubrication, a problem with the fuel injectors or a loose throttle.  

5) Black Exhaust Emissions 

Whether you own a diesel vehicle or you’ve just driven behind them, you’ll know that they often emit more smoke than regular vehicles.

But, excessive black smoke pouring out of your exhaust is far from normal. This is usually a sign of an imbalanced air to fuel ratio, meaning that you’ve overfilled the tank with too much fuel. As such, you can overcome this problem by going easier on the fuel next time you fill up the tank. 

If that’s not the cause of the black smoke, your vehicle may have a fuel nozzle or a needle which needs to be replaced. Other potential causes are a fault injector pump, air filter, injector, turbocharger or an EGR valve. You may be able to replace some of these yourself but if you’re not sure of the root of the issue, get it checked out straight away.   

6) Excessive Noise

Diesel engines are naturally louder than other vehicles and can make a significant amount of noise.

But, excessive noise or strange sounds can be a sign of common diesel engine problems. If you notice inconsistent noise or a knocking sound in the engine, this may indicate that there is an issue with the fuel injectors. This can affect the compression balance and reduce performance so it’s important to get any unusual noises checked out. 

7) Oxidized Oil

Diesel cars don’t tend to be as at much of a risk of the oil oxidizing since they are used often by their owners. But, diesel trucks, which can be left in storage for long periods, or only used during certain seasons, can have problems with oxidized oil. 

Oxidized oil means that air has entered into the oil. This creates bubbles and can disrupt proper lubrication. As a result, the engine can falter or become damaged. A way to avoid this problem is to change the oil as soon as possible after this period of inactivity. 

8) Damaged Glow Plugs 

Unlike gasoline-powered cars which rely on spark plugs to ignite the mixture of fuel and air, diesel cars use glow plugs. These glow plugs ignite the mixtures via a high-resistance element similar to that found in a toaster. 

If one or more glow plugs is damaged or compromised in some way, you’ll find that it’s near-impossible to start your diesel engine, especially in cold weather.

But, the good news is that glow plugs are pretty simple to replace yourself. To be on the safe side, replace all four of them at the same time. Even if only one of them has gone, it won’t be long before they all start to fail.  

Common Diesel Engine Problems 


Many people prefer diesel vehicles for their powerful performance, smooth ride and efficiency. But, there are a range of diesel engine problems that it’s important to know about to ensure that you get the most out of your motor. 

One such issue is the pressure that extreme temperatures can put on your diesel engine. To make sure your vehicle is in tip-top shape no matter the weather, check out these seasonal car maintenance tips


  • Zachary Tomlinson Says

    Thanks for elaborating on how a damaged engine part can affect your vehicle’s performance! I’ve been thinking about purchasing a van that’ll let me travel around the country. I’ll keep this in mind and locate a car engine repair expert as a preventive measure!

  • Alice Carroll Says

    Thanks for pointing out that oxidized oil is also a common thing that can be a problems for diesel engines. I’d like to know more about car engine repair services because I might need to have my car checked for that soon. I haven’t had maintenance for it in so long so I can see why it is starting to act up.

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