The fuel injection system decides how precisely a diesel engine meters and times its fuel. That affects fuel consumption, emissions, smoke during load changes and how the engine is serviced. The Jichai engines we supply use different injection systems depending on the series. This guide explains the three main types and how to weigh them for your project.
What the injection system has to do
It must deliver the right quantity of fuel, at the right moment, at a pressure high enough to atomize the fuel as it enters the cylinder. Higher pressure gives a finer spray and better mixing with air. Timing and quantity decide how completely the fuel burns, and so how much fuel the engine uses and what it emits.
Mechanical pump systems
In a mechanical system a cam-driven pump raises the fuel pressure, and injection quantity and timing are set by the pump design and a mechanical governor. These systems are simple, robust and tolerant of variable fuel quality, and they can be repaired in the field with basic tools. Their limits are that injection pressure depends on engine speed and timing cannot be adjusted freely, which makes stricter emission limits harder to meet.
Electronic unit pump
Each cylinder has its own pump, driven by the camshaft, with a short high-pressure line to the injector. A solenoid valve controlled by the engine ECU decides when injection starts and how much fuel is delivered. The result is precise, flexible control while keeping the robustness of a cam-driven pump. Pressure is still generated by the cam, so it remains linked to engine speed.
The L200 series uses electronic unit pump technology to control injection quantity, timing and pressure precisely. This improves combustion and reduces emissions, and together with other changes it gives about 10% more power and torque than the L190 series in the same external dimensions.
High-pressure common rail
A high-pressure pump feeds a common rail, an accumulator that holds fuel at high pressure regardless of engine speed. The ECU opens each injector electronically and can split injection into several events per cycle. The engine therefore gets high injection pressure even at low speed and light load, with finer atomization, lower fuel consumption, lower emissions and smoother response to load changes. In return, common rail needs very clean fuel and good filtration, and service teams need electronic diagnostic tools.
The 175 series combines electronic control and high-pressure common rail with the Miller cycle, reaching a fuel consumption of 198 g/kWh, a first overhaul at 35,000 hours and US EPA Tier 2 emissions. The medium-speed 26/32 series uses a common rail fuel system with dual electronic control and a strong Miller cycle, with fuel consumption of 184 g/kWh or less.
Side-by-side comparison
| Mechanical pump | Electronic unit pump | Common rail | |
|---|---|---|---|
| Pressure generation | Cam-driven, depends on speed | Cam-driven pump per cylinder, depends on speed | Separate pump and rail, independent of speed |
| Timing and quantity | Set mechanically | ECU-controlled solenoid | ECU-controlled injectors, multiple injections possible |
| Fuel cleanliness needed | Least demanding | Moderate | Most demanding, fine filtration |
| Fuel use and emissions | Hardest to optimize | Improved | Best potential |
| Field service | Simplest | Needs ECU diagnostics | Needs ECU diagnostics and clean handling |
Which engines in our range use which system
- 175 series (1,370–1,766 kW): electronic control with high-pressure common rail
- 200 series (700–1,650 kW): electronic unit pump with ECU speed control
- 4000 series (1,200–1,300 kW): electronically controlled or mechanical single unit pump, depending on the model
- 26/32, 27/38 and 32/40 series (2,080–4,500 kW): high-pressure common rail
- 2000, 3000 and 6000 series: ask us for the fuel system of the specific model
How to choose
- Emission rules. Check the limits where the engine will run. The 175 series meets EPA Tier 2, and the 27/38 series meets IMO Tier II.
- Fuel quality on site. In remote oil fields, plan filtration and water separation, especially for common rail engines.
- Service capability. Electronic systems need diagnostic tools and trained technicians close to the site.
- Load profile. Drilling rigs and generator sets see frequent load changes, which benefit from precise electronic control.
- Fuel cost over the engine’s life. A few grams per kWh add up over thousands of running hours.
Compare every series on our diesel engines page, see the emission and performance standards, or read how to choose a diesel engine for a drilling rig.
Request a quotation
Tell us your application, required power, speed, fuel, voltage and frequency using our RFQ guide or the contact page. You can also email nora@qdhailong.com or call +86-532-66090318.