Common Injector Issues in Mitsubishi 4N14 and 4N15 Engines

Mitsubishi diesel engines, particularly the 4N14 in the Outlander and the 4N15 in the Triton and Pajero Sport, have gained a reputation for efficiency and reliability. However, like any advanced diesel engine, they are not without issues. One of the most common problems car owners face is Mitsubishi fuel injector failure, primarily due to strict emission standards and their impact on engine components.

This blog will explore common injector issues in Mitsubishi 4N14 and 4N15 engines.

Understanding the Injector Issues in Mitsubishi 4N14 and 4N15 Engines

The 4N14 and 4N15 diesel engines are designed to meet stringent emission regulations. However, this compliance often comes at a cost. These engines require valve adjustments every 40,000 km, a process that involves removing and refitting the injectors multiple times. Repeated removal can cause improper seating, leading to blow-by, which is when combustion gases escape past the injector seals. Over time, this results in increased wear, reduced efficiency, and major engine problems.

Ironically, the technology designed to reduce emissions can cause failures that lead to higher emissions, making it counterproductive. This has become a significant concern among Mitsubishi Triton, Pajero Sport, and Outlander owners, as injector issues can lead to DPF failures, engine oil dilution, and fuel system damage.

Common Injector Failure Symptoms in 4N14 and 4N15 Engines

If you're experiencing any of the symptoms below, your Mitsubishi diesel engine may have injector-related issues:

1.  DPF Constant Regeneration – White Smoke and Diesel Smell

1. • One of the first signs of injector seat blow-by is the Diesel Particulate Filter (DPF) going into frequent regeneration cycles.

   • When injectors are not seated correctly, compression leaks occur, causing incomplete combustion and leading to excess soot buildup in the DPF.

   • This results in white smoke from the exhaust and a strong diesel smell.

   • The ECU triggers regeneration more frequently, increasing fuel consumption and affecting engine performance.

   • Over time, the DPF can become clogged, leading to expensive repairs or replacements.

2.  Engine Oil Level Rising

   • Another concerning symptom of injector issues is increasing engine oil levels.

   • This happens when the ECU repeatedly triggers DPF regeneration, allowing unburned fuel to mix with engine oil.

   • Diluted oil loses its lubricating properties, leading to excessive engine wear.

   • If left unchecked, it can cause engine knocking, increased friction, and even complete engine failure.

   • This issue is commonly reported in Mitsubishi Triton 4N15 and Pajero Sport models with high mileage.

3.  Misfire or Non-Start Due to Injector and Pump Failure

   • Another serious problem linked to injector issues is fuel pump failure.

   • Metal contamination from a failing high-pressure fuel pump can cause injector jamming, leading to:

   • Engine misfires or rough idling

   • Difficulty starting or a complete non-start condition

   • Loss of power and poor acceleration

   • In severe cases, both the injectors and the fuel pump need replacement, adding to costly repairs.

Causes of Injector Failures in Mitsubishi 4N14 and 4N15 Engines

Here are some of the causes of injector failures 

• Frequent Injector Removal for Valve Adjustments

  • The 4N15 Triton, Pajero Sport, and 4N14 Outlander engines require regular valve adjustments, leading to multiple injector removals and refits.

  • Improper reinstallation can cause injector seat blow-by, allowing combustion gases to escape.

• High-Pressure Fuel Pump Wear

  • The common rail diesel system in these engines relies on a high-pressure fuel pump, which can degrade over time.

  • If the pump fails, metal debris contaminates the fuel system, leading to injector blockage and fuel starvation.
    

• Poor-Quality Diesel Fuel

  • Low-quality or contaminated diesel fuel can clog injectors, reduce efficiency, and cause premature wear.

  • Regular use of high-quality diesel and fuel additives can help prevent carbon buildup and injector failures.

• Excessive DPF Regenerations

  • The DPF system in the Mitsubishi 4N15 and 4N14 engines is designed to burn off accumulated soot.

  • However, frequent regenerations can lead to excess fuel entering the engine oil, reducing lubrication and causing long-term damage.

Preventative Maintenance for Mitsubishi 4N14 and 4N15 Injectors

To avoid costly injector failures, follow these maintenance tips:

• Ensure Proper Injector Seating – When performing valve adjustments, ensure that injectors are correctly torqued to prevent blow-by and compression leaks.

• Regular DPF Maintenance – A clogged DPF in Mitsubishi Triton, Pajero Sport, or Outlander can accelerate injector wear. Routine cleaning and proper driving habits (highway driving to aid regeneration) can help prolong DPF life.

• Monitor Engine Oil Levels – If you notice engine oil rising without an obvious reason, get the injectors and DPF system checked.

• Fuel System Inspection – Regularly inspect the high-pressure fuel pump for early signs of failure to prevent metal contamination in the injectors.

• Use High-Quality Diesel Fuel – Opt for premium diesel and fuel additives to minimise carbon buildup and injector wear.

Why Choose TL Ranger Diesel?

TL Ranger Diesel is a trusted supplier of high-quality injectors for Mitsubishi diesel engines, including the 4N14 and 4N15 models. We offer:

• Affordable Injector Replacements – High-quality injectors at cost-effective prices.

• Half-Price Exchange Program – Return old injectors and receive a 50% discount on replacements.

• Fast Australia-Wide Shipping – Quick delivery to minimise vehicle downtime.

• Injector Testing & Servicing – Available at significantly lower costs than competitors.

• Reliable and Performance-Driven Injectors – Supplying injectors for Mitsubishi Triton, Pajero Sport, Outlander, Toyota Hilux, Land Cruiser, Prado, Nissan Navara, and other diesel models.

Takeaway

The Mitsubishi 4N14 and 4N15 injector issues are a prime example of how strict emission controls can sometimes lead to unintended mechanical failures. Proper maintenance, regular inspections, and addressing symptoms early can help extend the life of the DPF, injectors, and fuel pump, ensuring a reliable driving experience.

For high-quality injector replacements at competitive prices, contact TL Ranger Diesel today to get the right injectors for your Mitsubishi 4N14 and 4N15 engines.