Diesel (ON) injection pumps

Genesis and application.

The genesis and evolution of diesel engine injection pumps is a fascinating story of technological progress that began in the late 19th century. Rudolf Diesel, a German engineer, invented the diesel engine in 1893, aiming to create a more efficient solution than the steam and internal combustion engines of the time. In the early years, very primitive fuel injection systems were used with low precision, resulting in limited efficiency and reliability of these engines.

The 1920s and 1930s saw significant progress with the introduction of mechanical injection pumps, driven directly by the engine. These pumps, such as the model developed by Bosch, became popular in cars and agricultural machinery, allowing fuel to be delivered to the cylinders more efficiently.

The next step in development was the distributor pumps, introduced in the 1950s. They allowed more precise control of fuel injection, which improved engine performance and economy. Examples include VE-type pumps, which were widely used in cars and trucks. The 1960s saw the advent of in-line pumps, which had separate sections for each cylinder, allowing more precise control over the amount of fuel injected and were used in large trucks and construction machinery.

The 1980s and 1990s saw a revolution in fuel injection technology with the introduction of electronic control. Electronic control units (ECUs) began to manage the operation of the injection pumps, enabling even more precise control of the combustion process. The EDC (Electronic Diesel Control) system from Bosch is an example of this.

A breakthrough in fuel injection technology for diesel engines came with the introduction of common rail systems in the late 1990s. This system separates pressure generation from the injection process, enabling very high injection pressures and precise control of fuel dosage. Fuel is stored in a common (rail) tank and delivered to the injectors at high pressure, allowing higher combustion efficiency and lower exhaust emissions.

The injection systems in use today are characterised by high precision, high injection pressures of up to 2,000 bar and advanced electronic control.

Diesel injection pumps have come a long way in their development from primitive, mechanical systems to high-tech, electronically controlled common rail systems, resulting in significant improvements in the efficiency, reliability and environmental performance of diesel engines.

Construction and principle of operation.

In-line injection pump.

Within the casing of this type of pump are piston sections, arranged in a row, corresponding to the number of engine cylinders. Each delivery section consists of a piston and a cylinder. The piston moves in the cylinder, compressing the fuel under the movement of the cam roller, which converts the rotary motion into reciprocating motion. The cam shaft is the key element that drives the pistons, allowing the fuel to be compressed. The operation of the pump is controlled by a speed controller, which can be mechanical or electronic. It is responsible for controlling the engine speed by regulating the amount of fuel delivered to the cylinders. At the outlet of each delivery section, there are injection valves that open under fuel pressure, allowing the fuel to flow into the lines leading to the injectors. The lines transport the pressurised fuel to the injectors, which inject the fuel into the engine combustion chamber. The adjuster mechanism allows the timing of the start of fuel injection to be adjusted, which is crucial for optimum engine operation under various load and speed conditions. The operation of the in-line injection pump is sequential. A cam shaft, driven by the engine, controls the movement of the pistons in the individual delivery sections. The pistons compress the fuel in the cylinders of the sections, and the correspondingly high pressure causes the injectors to open and fuel to be injected. The rev regulator controls the amount of fuel delivered to the cylinders and the adjuster mechanism allows the injection angle to be adjusted, which is crucial for efficient combustion and engine performance.

Distibutor injection pumps (VE/VP).

Axial and radial distributor pumps are encountered on the market. The difference lies in the element(s) used to generate high fuel pressure inside the injection pump. A drive shaft, connected to the engine, drives the moving parts of the pump, rotating the delivery elements and synchronising their operation with the engine. The distributor, alongside the fuel compression elements, is the key component of the pump, responsible for distributing fuel to the individual cylinders. It rotates inside the pump body, driven by a drive shaft. The vane pump, located in the intake section, is responsible for drawing in fuel from the tank and pre-compressing it before delivering it to the delivery elements. The delivery element, consisting of a piston and cylinder, compresses the fuel to a high pressure. The movement of the piston is synchronised with the rotation of the drive shaft. A control valve controls the amount of fuel supplied to the piston element, allowing precise fuel dosage according to engine demand. In older designs, both the injection angle and fuel dosage were regulated mechanically or pneumatically. Newer distributor pumps are equipped with an electric adjuster or electronic control unit. The latter in particular allow relatively precise and fast adjustment of the fuel injection parameters, thanks to the pump's corresponding operating algorithm stored in its controller.

Unit pump (individual PLD/UPS/EUP injection units).

The unit injection pump is an advanced fuel injection system used mainly in large-capacity and powerful diesel engines. This solution is used in commercial vehicles such as trucks, agricultural and construction machinery. Each engine cylinder has its own separate fuel injection pump, which allows for very precise control of fuel injection.

At the heart of the PLD unit pump is the pump body, which is made of robust materials such as steel or cast iron to withstand high pressures and loads. Inside the body is a piston that moves in a cylinder. This piston is driven by a cam shaft, which converts the rotary motion of the shaft into reciprocating motion of the piston. The cam shaft is synchronised to the engine, which allows precise control of the fuel injection timing. Each pump is fitted with an electro-valve which, controlled by the engine controller, opens to allow fuel to flow into the lines leading to the injectors. This valve also controls the amount of fuel delivered to the combustion chamber, which is crucial for efficient combustion. The injectors, connected to the pumps, inject fuel directly into the combustion chamber at very high pressure, ensuring better fuel atomisation and more efficient combustion. 

The PLD system is characterised by its high precision and reliability, as well as its ability to accurately control fuel injection in each cylinder individually. This enables engines equipped with unit pumps to achieve better combustion efficiency, lower emissions and higher performance. The overall design of the PLD pump is designed to ensure long-lasting and reliable operation under harsh operating conditions, as well as quick service in the event of failure.

High-pressure pumps (common rail).

The high-pressure pump in a common rail system is the key component responsible for generating and maintaining high fuel pressure, which is then delivered to the rail (common rail) and from there to the injectors. The design of this pump includes several important components that work together to ensure efficient and reliable operation.

The pump body, usually made of strong materials such as steel or cast iron, is the basic structure in which all the key components are mounted. Inside the body is the shaft that receives the drive from the engine. The drive shaft, through cams and pushrods, drives the delivery elements, which compress the fuel to a high pressure. The high pressure sections consist of pistons located in the cylinders. The movement of the pistons is generated by a cam shaft, which converts the rotational movement of the drive shaft into reciprocating movement of the pistons. The pump is equipped with inlet and outlet valves that control the flow of fuel to and from the piston elements. The intake valves open when the pistons move downwards, sucking in fuel into the cylinders, and the exhaust valves open when the pistons move upwards, compressing the fuel and pumping it into the rail. Most high pressure pumps have one to three high pressure sections.

Depending on the model, this type of pump is equipped with an solenoid valve for controlling the pressure/fuel output. Fuel temperature sensors and solenoid valves disconnecting one high pressure section are also used as accessories. An solenoid valve mounted in the pump or on the rail, controlled by the engine control unit (ECU), regulates the fuel pressure in the common rail system. Some high pressure pumps have an integrated fuel feed pump, which is responsible for sucking in the fuel from the tank and pumping it to the high pressure section for compression. 

Remanufacturing process.

Bosch distributor pumps VP29/30 and VP44.

The remanufacturing process begins by reading the contents of the pump controller's memory and verifying the stored errors. The pump components are then disassembled and the mechanical parts are inspected. During pump remanufacturing , all key components are replaced or repaired, including: electronic control unit, speed sensor, feed pump, injection angle adjuster, high-pressure pistons, dose and injection angle solenoid valves, head or housing. Once the new parts have been fitted, the pump is transferred to the Bosch EPS 815 test bench with the VPM844 attachment. There, a fully automatic process is carried out to test and calibrate its operating parameters. A positive result from this process guarantees that the correct fuel delivery rate and injection angle are maintained across the entire engine speed and load range.

Bosch (PLD/UPS) and Delphi (EUP) unit pumps.

Thanks to the Bosch CAMBOX attachment, our offer also includes the testing and remanufacturing of pumps included in individual Bosch PLD/UPS injection sets. The remanufacturing of this type of pump involves the replacement of a set of seals as well as inspection, cleaning and possible replacement of other elements such as the control solenoid valve or elements generating high pressure. The final test of the pump takes place on a Bosch EPS 815 test bench equipped with the mentioned attachment.

We also offer performance testing and remanufacturing of pumps from Delphi EUP systems. Inspection of components takes place on a suitably equipped Hartridge AVM2-PC test bench. Remanufacturing usually includes replacement of seals, control valve. piston and inspection and cleaning of the remaining parts. If necessary, damaged components such as the spring, valve, solenoid or electrical connector are replaced. The remanufactured pump is given a new correction code, which is generated on the basis of the parameters measured during the calibration test carried out on the test bench.

Common rail high pressure pumps Bosch, Delphi, Siemens VDO/Continental, Denso.

The process begins with a pump test, which is preceded by the replacement of a set of seals. Bosch and Hartridge test benches equipped with appropriate instrumentation are used to test CR pumps. Remanufacturing of the pump includes replacement of damaged or worn out components such as, for example: feed pump (if present), solenoid valves, mechanical valves, drive shaft, pistons or housing. Each repair is completed with a test, during which the key pump parameters - pressure and fuel flow - are measured.

Causes and types of damage.

Symptoms that may indicate a faulty injection pump:

1. Difficulty starting the engine.
2. Uneven engine idling.
3. Decrease in engine power, especially during acceleration.
4. Increased fuel consumption.
5. Excessive smoke from the exhaust system. 
6. 'Check engine' light or other fault indicators on the dashboard. 

The most common failures of injection pumps are:

1. Wear on the pistons and inner cylinders of the pump.
2. Damage to gaskets and sealing rings.
3. Failure of the control solenoid valve.
4. Problems with mechanical components such as the drive shaft, cams, pushrods or piston components.
5. Damage to the electronic control units (ECU) responsible for controlling pump operation.
6. Contamination of the fuel which leads to seizure or blockage of moving parts of the pump.
7. Fuel supply problems, such as clogged fuel filters or poor fuel quality, leading to internal damage.