What Causes A Diesel Engine To Lose Power While Driving?

Published on 06/30/2023

what causes a diesel engine to lose power while driving

Diesel engines power some of the biggest sectors of the U.S. economy. From agriculture and construction to consumer products, the commercial trucking industry relies on durable vehicles and high-quality fuel to keep supplier chains running. Therefore, operators of heavy-duty vehicles need a reliable ride.

For professionals who rely on a strong diesel engine, a loss of power can create dangerous problems. But what causes a diesel engine to lose power while driving?

6 Possible Reasons Your Diesel Engine Is Losing Power

If your diesel engine is experiencing power loss, you may need to contact a mobile diesel repair service in the Bay Area. In the meantime, it may help to learn about the possible complications so you can develop a clearer idea of what might be going on. This article will discuss what causes a diesel engine to lose power while driving and possible solutions to your power problems.

The fuel filter is clogged

A clogged or dirty fuel filter is one of the most common causes of power loss in diesel engines. The fuel filter protects the engine from any impurities that have found their way into the fuel, but a clogged filter can no longer do its job effectively. 


Although a clogged fuel filter might not be the only thing preventing your engine from operating at full power, checking the filter when power issues arise is always a good idea. A lot of diesel engines contain two filters — one primary and one secondary — so if your engine has two, it’s a good idea to replace both at the same time.

Likewise, if replacing the filters improves the loss of power, be sure to clean out the old filters and examine what might’ve caused the clog. Depending on what you find, you may also need to drain and refill your tank to improve the fuel quality.

The “check engine” light is on

You may read this and think, “Isn’t this problem obvious?” Of course, the “check engine” light is a clear indicator of an engine issue, but let’s be honest: How often do you see it come on and ignore it?

We’re all guilty of it. However, it’s a safety feature designed to alert you to potential issues before they worsen. The problem may be small, but it’s best not to ignore it regardless.


When the “check engine” light comes on, contact a professional repair service to determine the problem. It’s always better to be safe than sorry.

The exhaust pipe is plugged

What causes diesel engines to lose power while driving will vary depending on a vehicle’s make, model, and age, but another common culprit is a clogged exhaust pipe. The engine’s catalytic converter and muffler help reduce the toxicity of exhaust fumes. When the exhaust pipe is clogged, the system can’t function as it should, and the engine struggles to reach full power.


Carefully clean the exhaust pipe to remove any buildup. You can use soap and water to gently remove debris and a long brush to clear out dirt and other impurities.

There are carbon deposits around the glow plugs

Gas and diesel engines differ when it comes to fuel, but they also have different parts. In particular, diesel engines don’t have spark plugs. Instead, they run on compression ignition. The glow plugs provide heat to the combustion chamber, which ignites with greater force and helps provide the power to haul heavy loads.

However, the anatomy of a diesel engine gives more opportunity for carbon deposits to form around the glow plugs, which can hinder the ignition process and cause a reduction in power.


How you remove carbon deposits depends on which part of the engine needs cleaning. In most cases, you can remove deposits by using a fuel additive. Other areas, such as the throttle body, may require manual cleaning.

The engine has an air leak

If you’re wondering what causes a diesel engine to lose power while driving, consider the intake air system. Most diesel engines contain a turbo that provides compressed air, but before reaching the engine, the air goes through the charge air cooler.

As the name suggests, this feature cools the air so the engine can function normally. If you have a leak in the air system, you’ll end up using more fuel while getting less power.


This problem can create a bit of a hassle, as it often requires more work to fix. Generally, you have two methods of checking for leaks in the air system:

  •     The turbo clamps may be loose. Check the clamps to ensure you have all of them lined up in the correct spot.
  •     The hoses may have holes. Over time, the hoses in the air system can rub together and wear each other down, so it’s important to check them for small holes or tears. If your engine’s hoses are silicone-based, you can check them by noting whether or not they collapse when the engine comes on.

Likewise, any clog in the air system may reduce the engine’s power. Check your air filter to ensure nothing is blocking or pinching the hoses.

The engine has low fuel pressure

Diesel engines are among the high-pressure automotive systems that enable drivers to haul heavy loads. If your diesel is experiencing low fuel pressure, it’s almost guaranteed that your engine’s power will suffer.


Check all your fuel lines for any leaks or looseness. If air enters the fuel lines, the engine’s power will reduce dramatically. Likewise, even if you find no holes, lines that sag or appear loose can impact the engine.

Contact Us To Solve All Your Engine Issues

Now that you’ve learned what causes a diesel engine to lose power while driving, you’re more equipped to solve problems on the road, but some issues require a professional eye. If you have a diesel engine that isn’t starting or is exhibiting power issues, call All Bay Diesel at (925) 522-1780 to speak with our friendly team.

Call Now: (925) 522-1780