ADVANCED FUEL SYSTEMS
This component in a Common Rail Direct Injection (CRDI) system is responsible for precisely timing and delivering fuel to each cylinder by opening and closing in milliseconds.
What is the fuel injector (or piezo/solenoid injector)?
This system recirculates a portion of exhaust gases back into the intake manifold to lower combustion temperatures and reduce NOx formation.
What is Exhaust Gas Recirculation (EGR)?
Excessive white smoke on a cold start that clears as the engine warms up typically indicates the presence of this in the combustion chamber
What is water or coolant?
While common in gasoline engines, this component is generally absent in naturally aspirated diesel engines because they rely on compression ignition.
What is a spark plug?
The theoretical thermodynamic cycle that most closely describes the operation of a diesel engine.
What is the Diesel Cycle?
In a CRDI system, the high-pressure fuel pump maintains pressure in this shared component, from which individual injectors draw fuel
What is the common rail?
Beyond the Diesel Particulate Filter (DPF), modern diesel engines often use this catalytic converter, which employs DEF to convert NOx into harmless nitrogen and water.
What is a Selective Catalytic Reduction (SCR) system?
A persistent rough idle, particularly at low RPMs, combined with a "hazy" or "wet" exhaust, could suggest an issue with this fuel system component
What is a faulty or leaking fuel injector?
Modern diesel pistons often feature an "omega" or "re-entrant" combustion bowl design to optimize this process
What is combustion efficiency or fuel-air mixing?
The extremely high compression ratio in a diesel engine leads to a significant increase in this physical property of the air before fuel injection.
What is temperature (or pressure)?
The process by which modern diesel injectors can deliver multiple small bursts of fuel during a single power stroke for quieter operation and reduced emissions.
What is multi-shot injection (or pilot/post-injection)?
The process where the DPF is heated to extremely high temperatures to burn off accumulated soot, typically triggered by the ECM.
What is regeneration?
A common cause for engine misfires or hard starting in colder climates due to insufficient heat for compression ignition.
What are faulty glow plugs or a glow plug control module?
High-performance diesel connecting rods are often made from this type of steel, known for its strength and fatigue resistance.
What is forged steel or high-strength alloy steel?
Explain how the delay period (ignition delay) in a diesel engine affects combustion noise and efficiency.
What is a longer delay period can lead to a harsher, more "knocking" combustion and potentially less efficient fuel burn, as more fuel is injected before ignition occurs?
This electronic control unit (ECU) sub-system monitors various engine parameters and calculates the optimal fuel quantity, injection timing, and injection pressure for each cylinder.
What is the Engine Control Module (ECM) or Powertrain Control Module (PCM)?
A clogged DPF can lead to increased exhaust backpressure, which can cause this effect on engine performance and fuel economy
What is a reduction in power or decreased fuel efficiency?
When diagnosing an intermittent power loss in a turbocharged diesel, technicians often check for issues with the VGT (Variable Geometry Turbocharger) actuator or this related sensor.
What is the boost pressure sensor?
The use of this type of valvetrain system, common in heavy-duty diesels, allows for precise control of valve lift and duration without a traditional camshaft.
What is a camless or electro-hydraulic valvetrain system?
This property of diesel fuel, measured by the cetane number, directly influences the ignition delay period.
What is ignitability?
Name two distinct types of fuel pressure sensors found in a modern CRDI system and their general locations.
What are a rail pressure sensor (on the common rail) and a low-pressure fuel sensor (often in the fuel line before the high-pressure pump)?
Explain the function of a DOC (Diesel Oxidation Catalyst) in a diesel aftertreatment system, specifically what it converts.
What is the DOC converts carbon monoxide (CO) and unburnt hydrocarbons (HC) into carbon dioxide (CO_2) and water (H_2O)?
Describe a scenario where a diesel engine might exhibit "limp mode" or reduced power, specifically relating it to a common sensor failure in the aftertreatment system.
What is a failed NOx sensor or a DEF quality sensor, causing the ECM to limit engine power to protect emissions compliance?
Beyond cast iron or aluminum, cylinder liners in high-output diesel engines are sometimes treated with specialized coatings or made from alloys containing this element for wear resistance.
What is chrome or nickel (or ceramics)?
When a diesel engine "runs away," it's often due to ingesting an uncontrolled source of fuel, leading to a dangerous positive feedback loop. Name two common external sources of fuel that can cause this.
What are engine oil (from a faulty turbo seal or excessive crankcase pressure) or combustible vapors in the intake air (e.g., from a ruptured fuel tank in an accident)?