The fuel injectors in your diesel engine are vital to the function and efficiency of your entire vehicle system. When working properly, fuel injectors increase fuel efficiency, make emissions cleaner, and help maintain your vehicle’s overall performance. After all, performance is why you chose a diesel engine in the first place.

On the other hand, issues with your fuel injectors can cause significant problems. Damaged or leaking fuel injectors can affect the entire vehicle and can even potentially cause engine failure and a lot of frustration down the line. That’s why it’s important to know how to spot a faulty injection system. If you know what to look for, you can spot issues before they get worse and lead to serious problems.

While the best Common Rail Injectors contribute to a smooth running engine, allowing for optimal vehicle performance, they can also be the cause of engine troubles. There can be a number of signs of fuel injector problems, but there are five common indications of damaged or leaking fuel injectors. Knowing these bad fuel injector symptoms can help you avoid larger engine problems. If you do notice any of these symptoms, you should call your mechanic immediately.

Top 5 Bad Fuel Injector Symptoms

Damage can occur to fuel injectors at any time, but it is more likely to occur near the end of their lifespan. On average, diesel fuel injectors last up to 100,000 miles. You always want to be conscious of the following symptoms, but you should be especially attentive as your engine ages.

  • Strong fuel odor
  • Lower fuel efficiency
  • Trouble starting
  • Engine misfires
  • Low RPMs


The smell of fuel emanating from your vehicle is always something you want to get checked out by your mechanic right away. It can be subtle at first, but the persistent smell of fuel is a strong sign that there is an issue with your fuel injectors. Diesel injectors require high pressure to function, and this pressure can drive the fuel out through a leak in the injector nozzle or tip, or in a line nearby.


In terms of your diesel fuel injectors, fuel efficiency is all about the right amount of fuel entering the engine chambers. When an injection system is performing as it should, your vehicle experiences the fuel efficiency it was designed to attain. The proper amount of fuel enters each chamber under the right pressure and is atomized accordingly. If, on the other hand, this process is happening incorrectly, your vehicle does not have the fuel it needs to function properly, decreasing your fuel efficiency. It might take time to notice as you gas up more frequently, but you definitely need to have your vehicle checked, particularly the fuel injection system if you notice this decrease.


This is one of the most glaring of the common bad fuel injector symptoms. If your vehicle is taking longer to start or is having trouble starting at all, especially when the tank is full, then it is a sign of a clogged or damaged injector.


Along with trouble starting, experiencing engine misfires is a clear bad fuel injector symptom. You will need to have your engine looked at by your mechanic as soon as possible to check if your injectors are leaking or clogged. It could lead to further engine problems such as stalling if the problem continues without being addressed.


Bad injector systems can cause damage to the entire engine if left untreated for too long. The symptom that illustrates this the most is when you experience lower RPMs. If the fuel injection system is clogged or leaking, your engine is not receiving enough fuel. This can leave your vehicle stuck on lower RPMs than usual. This can cause damaging stress on your engine as it is forced to work harder than it should, and needs to be addressed as soon as possible to avoid further damage.

Fixing Bad Fuel Injectors

Once you notice any of these common bad fuel injector symptoms, the first step is to bring your vehicle to a mechanic. Fuel injectors are relatively simple to diagnose once they are suspected as the cause of your engine performance issues. However, they can be difficult to identify with a computer because the symptoms can point to other areas. That’s another reason why being aware of symptoms of bad fuel injectors can help solve the problem.

The cause of poor fuel injector function is likely either leaking or clogging of the injectors. Your mechanic will test each one to determine which injector, or injectors, is the problem. Essentially, your mechanic will disconnect one injector at a time and cap it off. If performance issues remain, that injector is eliminated as the cause and reconnected, and then the next one will be tested.

Once the cause of your engine’s fuel injection issues is identified, your mechanic can fix the problem. Even the best Common Rail Injectors are subject to issues such as excess deposit buildup, which causes the system to fail due to internal or external deposits. If the injector is dirty, there is a good chance it can be cleaned and restored to its proper level of function. If the fuel injector is damaged, it will need to be replaced.

Get the Most from Your Fuel Injectors

Once you have your diesel injectors repaired or replaced, be sure to ask your mechanic how you can best maintain your system to avoid problems in the future. By knowing how to prevent fuel injection problems, combined with greater awareness of the symptoms of bad fuel injectors, you can avoid suffering significant damage to your engine in the future. You’ll also enjoy a diesel engine that performs to its full capability so you can get each and every job done right.

Another way to get the most out of your diesel engine is to choose high-quality fuel injectors. By opting for the best products out there, you can rest assured knowing your engine will perform the way you want it to. That’s why you should buy fuel injectors from Dieselogic. You need your diesel vehicle at its best, and maintaining high-quality fuel injectors will keep you running at your full potential, too.