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The fuel system in your Perkins engine is one of its most essential – and complex – components. While we make them as reliable as possible, the quality of fuel they use can inevitably cause a variety of issues. It is important that you understand what these issues are and how to maintain your fuel system to avoid potential problems and get the best performance from your engine.

Your fuel system comprises the following key components:

Fuel injection pumps

Fuel injection pumps

provide high-pressure fuel to each cylinder in mechanical engines or to the common rail

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Fuel transfer or lift pumps

Fuel transfer or lift pumps

deliver fuel from the tank to the injection pump via fuel filters

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Fuel nozzles

Fuel nozzles

are the tip of an injector, replaceable in some non-common rail systems

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Fuel injectors

Fuel injectors

also known as atomizers, deliver the fuel into the combustion chamber

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What is fuel injection?

Fuel injectors spray a specific amount of atomised fuel into the combustion chamber. The injectors in your engine are specially selected to provide the best combination of performance and fuel burn to meet the emission standards in your region. The fuel injector or atomiser is the last component the diesel fuel passes through before entering the cylinder. It is a very precise component designed to deliver a predetermined quantity of fuel into the combustion area at a high pressure and in a fine spray, so it will be easily burnt. Because of the high pressures all the dimensions are critical, with surface finish and component geometry precisely specified. 

 Types of fuel injector

Perkins engines use different fuel injectors depending on the control system and engine type. Injector actuation and control can be mechanical, hydraulically actuated electronic or mechanically actuated electronic. There are many design variations, but they fall into two basic categories: single-hole and multi-hole.

 Common rail injector systems

The fuel in an electronically controlled engine is stored at variable pressure in a cylinder or ‘rail’ connected to the engine’s fuel injectors via individual pipes, making it a ‘common rail’ to all the injectors. The pressure is controlled by a fuel pump, but it is the fuel injectors, working in parallel with the fuel pump, that control the timing of the fuel injection and the amount of fuel injected. In contrast earlier, mechanical systems rely on the fuel pump for pressure, timing and quantity.

A further advantage of the common rail direct injection (CRDi) system is that it injects the fuel directly into the combustion chamber. The indirect injection (IDI) system in older engines injected fuel into a pre-combustion chamber which then fed the main combustion chamber.

Typical fuel injector types include:

 Direct Injection

Direct injection allows air to swirl around the piston bowl. Fuel is directly injected into the piston bowl which forms the base of the combustion chamber. The fuel patterns from the nozzle and air turbulence from the swirl are matched to minimise emissions.

 Indirect Injection

Indirect injection forces air through the narrow throat that connects the cylinder to the combustion chamber. The narrow throat causes the air to accelerate quickly and the spherical combustion chamber then causes the air to circulate very rapidly.

 Mechanically Actuated Electronic Injector (MEUI)

MEUI systems are mechanically actuated but electronically controlled. Unit injectors are driven by a rocker arm that moves with the camshaft’s rotation. High fuel pressure is created in each injector using an integral plunger pump controlled by a rocker arm. MEUI systems provide variable fuel delivery and are virtually adjustment free.

 Hydraulically Actuated Electronic Injector (HEUI)

HEUI systems use hydraulic energy from pressurised engine lube oil to drive each injector. The pressure of the incoming oil controls the rate of injection, while the amount of fuel injected is determined by a signal from the ECM. The HEUI system’s high-pressure hydraulic pump features a built-in reservoir to immediately supply oil at cold starts. The electronically controlled Injector Actuation Pressure Control Valve on this pump controls oil pump output and injection pressure.

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