New Bobcat Gen2 Doosan Engine Fuel System Review – DM01 (D18), DM02 (D24), DM03 (D34)

Introduction to the Gen2 Doosan Fuel System

In 2020, Bobcat introduced its newer Generation 2 (Gen 2) Doosan D24 diesel engines, which use a modern Bosch fuel system. This meant Bobcat was moving away from the older Delphi fuel systems that had caused ongoing issues for equipment owners, including fuel system contamination and premature part failure. 

Well since then, the DM01 (D18), DM02 (D24), and DM03 (D34) engines have been completely redesigned. For equipment owners, fleet managers, and technicians, this swap over to the Bosch high-pressure common rail fuel system was aimed at improving performance and long-term reliability while still meeting modern emissions compliance standards.

In this article, we will break down exactly what changed, why it matters, how the system works and share tips on what mechanics and operators should watch out for when maintaining or repairing DM01 (D18), DM02 (D24), and DM03 (D34) Gen2 engines.

The Issue With the Gen1 Fuel Systems and Why Bobcat Moved to a Bosch Fuel System

The first-generation (D24, D34, D18) Doosan engines experienced widespread issues related to fuel contamination, inconsistent rail pressure, and catastrophic pump failures. In many cases, these problems stemmed from limitations in the original fuel system design, particularly when exposed to poor fuel quality, air intrusion, or fluctuating supply pressure.

Bobcat addressed these concerns by partnering with Bosch to design an improved high-pressure common rail system. Bosch fuel systems are widely used across on-highway and off-highway diesel platforms, known for precision, durability, and emissions compliance. This redesign significantly improves fuel delivery control, reduces failure risk, and increases overall engine reliability.

Who This Upgrade Matters Most To

• A mechanic servicing Bobcat skid steers, loaders, or compact equipment
  
• A fleet manager trying to reduce downtime
  
• An owner-operator diagnosing fuel-related issues
  
• A repair shop sourcing correct injectors or pumps

Overview of Gen2 Doosan Engines

DM01 (D18) Engine Overview

The DM01 (D18) is the smallest of the Gen2 lineup and is commonly found in compact Bobcat machines such as Compact Mini Excavators (E35, E38, E42, E50, E55, E40, E48, E50Z, E55Z). This engine has a displacement of 1.8 liters (1.8L), and produces a power output of 56 HP to 66HP. Despite its compact size, the DM01 runs a full Bosch common rail system, delivering strong efficiency and responsiveness for lighter-duty applications.

D24 (DM02) Engine Overview

The DM02 (D24) is the most common Gen2 Doosan engine on the market. This engine has a displacement of 2.4 liters (2.392L) and offers a power output ranging from approximately 49 HP to 75 HP. The DM02 is widely used across multiple Bobcat models including Track Loaders, Skid Steer Loaders, Telehandlers, Wheel Loaders and more. This engine is also where most technicians first encounter CRI2-18 injectors.

D34 (DM03) Engine Overview

The DM03 (D34) steps things up in power output and fuel demand. With a larger 3.4 liter (3.4L) displacement, this engine delivers approximately 74 HP to 130 HP, roughly a 25% increase. The DM03 engine is used across larger Bobcat machines including the B760 Backhoe Loader, E415 Large Excavator, T86 Compact Track Loader, S86 Skid-Steer Loader and numerous Telehandlers. With higher rail pressures and increased flow requirements, the Bosch system really shines here, but it also demands stricter maintenance discipline. Despite the increase in power, the DM03 engine has the same space requirements, which help with fitting the engine in existing applications. 

Gen1 vs Gen2 Fuel System Comparison

Delphi Fuel System (Gen1) Overview

The older Delphi fuel system used on Gen1 Doosan engines was simpler. This system relies on solenoid injectors, lower operating pressures, fewer sensors, and looser tolerances. This allowed it to survive marginal fuel quality better, but at the cost of efficiency, performance, and emissions control.

Bosch Fuel System (Gen2) Overview

The Gen2 Bosch system operates at significantly higher pressures and uses more advanced electronic control. This system uses electronically controlled magnetic solenoid injectors (CRI2-18 type), allowing for cleaner, faster, and more precise injection events. This improves combustion efficiency while reducing soot, noise, and emissions.

Key Performance and Reliability Differences

Think of it like switching from a carburetor to direct injection. The Bosch system is smarter and stronger, but it doesn’t tolerate shortcuts. Clean fuel isn’t optional, it’s mandatory.

Bosch Fuel System Components Explained

The system consists of four primary components: 

• Fuel Injectors
• High-Pressure Fuel Injection Pump
• High-Pressure Fuel Rail
• Fuel Lines
• Supporting sensors and control valves
  

CRI2-18 Fuel Injectors

CRI2-18 injectors are solenoid-controlled common rail injectors designed for high precision. Internally, they use a traditional Bosch high-pressure control valve and precision-machined nozzle to deliver fuel with extreme accuracy. Multiple injection events per cycle improve combustion efficiency and reduce engine knock.

These injectors are highly sensitive to contamination. Even minor debris can cause sticking, excessive return flow, or misfiring.

Each injector is assigned a unique trim code located on the top of the solenoid. Programming this trim code into the ECM is mandatory and directly impacts emissions compliance and engine balance. Failure to program injectors correctly can lead to rough running, increased emissions, and diagnostic fault codes.

CP4 High-Pressure Fuel Pump

The CP4 fuel pump is responsible for generating the extreme pressures needed by the Bosch system. It’s compact and efficient, but it has a reputation across the diesel industry for being intolerant of poor fuel quality. The pump includes:

• A fuel metering valve (also known as the inlet metering valve or IMV)
• A cam-driven plunger and head assembly
• A rear-mounted supply pump
• An overflow valve for pressure regulation

The pump is mechanically driven by the engine and electronically controlled by the ECM. When a CP4 fails, it often sends metal debris downstream, contaminating the rail, injectors and fuel lines.

One major advantage of the CP4 pump in this application is ease of installation. Because this is a high-pressure common rail system, traditional mechanical timing is not required.

High-Pressure Common Rail

The common rail acts as a pressure accumulator, ensuring consistent fuel delivery to each injector. Sensors continuously monitor pressure and communicate with the ECU to fine tune injection timing. Key common rail components include:

• A rail pressure sensor
• A pressure limiting valve for overpressure protection
• One high-pressure fuel inlet fitting
• Three or four injector outlet fittings (depending on engine configuration)
• A fuel return barb
  

Benefits of the Bosch Fuel System in Bobcat Equipment

Improved Fuel Efficiency

More precise electronic control over injection timing results in lower fuel consumption for the same output, reducing operating costs. Operators often notice better fuel economy, especially under steady loads.

Better Cold Starts and Throttle Response

Multiple pilot injections help engines start smoother in cold conditions and respond more quickly to throttle input.

Reduced Emissions and Smoother Operation

The optimized and cleaner combustion process reduces exhaust pollutants, helping the engine meet strict emission standards like Stage V. Less smoke, quieter operation, and cleaner exhaust are all direct results of tighter fuel control.

Common Issues Seen in Gen2 Bosch Fuel Systems

Fuel Contamination Sensitivity

Water or debris is the number one killer of Bosch systems. High-pressure common rail components operate with extremely tight tolerances, and even fuel that “looks clean” can cause damage. Any amount of dirt, debris, or water can cause damage. This type of contamination often stems from poor maintenance, bad quality fuel, condensation in the fuel tank, or failure to properly clean the fuel system after a prior failure.

CP4 Pump Failure Risks

Low lubricity fuel or infrequent filter changes dramatically increase CP4 failure risk.

Injector Wear and Return Flow Issues

Excessive return flow is a common symptom of injector wear. If left unchecked, it leads to hard starts and power loss.

Maintenance Tips for Gen2 Fuel Systems

Fuel Quality and Filtration Best Practices

Always use high-quality and low sulfur diesel and stick to recommended micron ratings on filters. Only buy OEM fuel filters, directly from Bobcat. This is not an area to save money.

You can also use Bobcat-approved stabilizers or biocides to prevent fuel from degrading and microbial growth.  

Service Intervals and Preventive Maintenance

Change fuel filters on time, or early if operating in dusty or remote environments. Every 250-500 hours is a good rule of thumb. 

Early Warning Signs to Watch For: 

• Hard starting
• Rough idle
• Loss of power
• Check engine or rail pressure codes

Ignoring these signs is like driving on a flashing oil light.

Fuel System Upgrade and Replacement Considerations

If contamination occurs, partial repairs often lead to repeat failures, especially if your fuel system and tank have not been properly flushed. Full kits with the fuel pump, injectors, rail, and lines are usually the safer long-term fix.

The Gen2 Bosch fuel system in Bobcat Doosan engines is a major step forward in performance and efficiency, but it demands respect. Cleaner fuel, stricter maintenance, and correct parts selection are non-negotiable. When serviced properly, these systems run strong and smooth. When neglected, they fail fast and expensively.

If you’re diagnosing issues, planning maintenance, or sourcing replacement components, contact Expert Diesel Parts for knowledgeable support and application-specific solutions. Getting it right the first time is always cheaper.

The information provided in this article is for general guidance only. Always refer to your machine’s manual or consult a qualified mechanic before performing any maintenance or repairs. We are not affiliated with or authorized by Bobcat Company. All trademarks are used descriptively to indicate part compatibility.