If you don’t already own one, right now is a great time to find a diesel truck for sale. With diesel prices dropping across the nation, it makes it a more economical choice, and the extra power and excitement they offer isn’t necessarily a downside either.

It’s important to note, however, that diesel trucks aren’t invincible. Like any vehicle, they come with their share of potential problems. If a defective diesel engine isn’t properly serviced, it can cause internal combustion, potentially wreaking havoc on your entire truck.

Here at Texas Diesel Co — your go-to diesel mechanic in the Dallas and Fort Worth area — we have compiled a list of some of the most common diesel truck repairs we come across in our diesel shop for you to keep an eye out for. If you find any of the following problems occurring with your truck, don’t hesitate to schedule an appointment with our diesel mechanics!

10 Most Common Diesel Problems

Oxidized Oil

Diesel trucks that sit in one place too long, are driven infrequently, or are kept in storage between seasons often have problems with their oil oxidizing. In other words, air gets into the oil and creates bubbles that can interfere with the proper lubrication of your engine’s components. This can result in a faltering or damaged engine if left unaddressed. Even though the oil isn’t technically dirty, it needs to be changed as soon as possible after this idle period. So when taking your truck out of a period of hibernation, be sure your first time starting it up is to take it to your local diesel mechanic to have the oil changed.

Hard Starting

Some diesel engines have a difficult time starting or they can experience delayed starts. This is usually a sign of low compression or an issue with how the fuel is being delivered. Some diesel engines simply crank a little when you start them, which is perfectly normal. But if your diesel truck has an extremely difficult time starting, cranks more than normal, or won’t start at all in some instances, it’s important to get things under the hood checked out by a diesel mechanic soon as possible.


While most diesel owners are fond of a loud engine, significant amounts of noise from a diesel engine can often be a sign of something wrong. Diesel engines are naturally louder than other vehicles, but if you notice inconsistent noise or distinct knocking sounds originating from the engine, this could be a sign of a problem with the fuel injectors, which can affect the compression balance and reduce the overall performance and lifespan of your diesel engine.

Contaminated Fuel

Because diesel is much more viscous than gasoline, it can become more easily contaminated by external elements in its environment. The four most common, and equally dangerous, diesel fuel contaminants include glycol, dilution, soot, and water. If any of these contaminants penetrate the fuel system, they can lead to major engine disruption. We’ve had countless diesel owners come into our diesel shop in Dallas due to engine complications that seemed to have come from out of the blue. Nine times out of ten after running a diagnostic test, contaminated fuel is the initial cause that leads to a truck needing repairs from our diesel mechanics.

Black Exhaust

If you’ve driven behind a diesel truck, you know that they generally exhibit more smoke than your traditional truck. They can also release a very noxious odor that can stink up the cab and make it difficult to breathe. Not to mention, you’ll likely be slapped with a hefty fine for ignoring the clean air ordinance in Texas or your respective state.

This black exhaust is generally a result of an imbalanced air to fuel ratio, leaning on the side of too much fuel and not enough air. A faulty injector, injector pump, air filter, EGR valve, or even turbocharger could be the root of the problem. While some diesel drivers like the “black smoke effect,” not allowing enough air into your tank can lead to a multitude of potential problems down the road for your truck.

Humidity Reactions

Water is another element that can contaminate the lubricant in a diesel engine and cause some adverse reactions. If a truck sits for too long or idles for an extended period of time in a humid or precipitous area, the overhydration can cause the engine to knock. Water attacks additives and increases the oxidation of oil. It can also interfere with the lubrication process, which we’ve already discussed can lead to a variety of potential problems and needed diesel repairs.

Lack Of Power

Another fuel-related problem manifests itself within a lack of power. This is an issue to be concerned about if you find your diesel does not accelerate quite like it used to. Dirty fuel filters, loose throttle linkage, excessive lubrication, and issues with the fuel injectors can all be factors that lead to this issue.

Failing Lead-Acid Storage Batteries

There’s often a heavy load on the lead-acid storage battery, which is a very essential component in a diesel engine’s starter system. If the storage battery malfunctions or doesn’t work properly, it can cause an imbalanced compression ratio, which can influence the starter system in a negative manner.

Defective Glow Plug

Diesel engines don’t have spark plugs to ignite the fuel-air mixture in their cylinders like gasoline-powered cars do. They rely on glow plugs to ignite the mixtures through a high-resistance heating element, similar to the coils in a stove or toaster. When the glow plug goes bad, it makes it nearly impossible for the engine to start, especially in colder weather.

Higher Compression Ratio

The average diesel engine has a compression ratio of 20:1, while the average gas-powered engine has an average ratio of 8:1. This high compression ratio makes the engine more powerful, smooth, and oftentimes more efficient, but it can also lead to issues if it gets too high. For example, it can cause the engine to knock more often as a result of an undesirable burn pattern, and it can also contribute significantly to fuel injection problems.

If you have come across any of these problems with your diesel truck recently, it’s in your best interest to have them addressed by your local diesel mechanic before the problems worsen! If you’re a diesel truck owner in Dallas or Fort Worth, contact our diesel shop — Texas Diesel Co. Our Top Rated Local® diesel mechanics have seen it all, and they can help you get your truck back in pristine condition in no time!

If your diesel isn’t experiencing any of the problems above, you can also consider upgrading your diesel performance with us!