Diesel Fuel Systems : The quiet diesel evolution

The quiet diesel evolution

Clean biodiesel fuels, dual fuel CNG/diesel injection systems and similar innovations are helping to clean up diesel emissions—and so are microprocessors. The improvements made in the last few years to light-duty diesel engines are very impressive. Automobile technicians sometimes tend to avoid servicing diesels, but it’s time to reconsider; today’s diesel technology is  fascinating, and a deeper understanding could prove beneficial.

Diesel Fuel Systems : Diesel electronic control

• Diesel electronic control systems
• Common rail diesel injection system
• HEUI diesel injection system

Diesel electronic control systems

Diesel engines are subject to very high stresses during compression and ignition, and increasingly stringent emission standards have made better control of the diesel combustion process necessary.
Electronic controlled diesel systems give very precise control of the fuel injection and combustion process. Electronic controls have delivered other benefits besides a reduction in fuel consumption and emissions, such as an increase in power and torque; improved engine responsiveness; a reduction in engine noise and diesel knock; and improved and expanded diagnostic capabilities through the use of scan tools.
Diesel electronic control systems monitor and control many variables, including:

Diesel Fuel Systems : Diesel fuel system components

• Diesel tanks & lines
• Diesel fuel filters
• Lift pump
• Plunger pump
• Priming pump
• Inline injection pump
• Mechanical or pneumatic governors
• Distributor-type injection pump
• Diesel injectors
• Glow plugs
• Cummins & Detroit Diesel injection

Diesel tanks & lines

The fuel tank stores fuel in a convenient location, away from the engine. It is commonly made of steel or aluminum. Baffles ensure the pickup tube is always submerged in fuel. This stops air entering the system. The inside of the tank can be treated to prevent rust. Galvanizing must never be used, because diesel fuel, reacts with zinc to produce powdery flakes that can block fuel filters.
A diesel fuel tank should be kept full, to prevent water condensing on tank surfaces and contaminating the fuel.

Diesel Fuel Systems : Clean diesel technology

Clean diesel technology

VW started the light-duty diesel revival with its modern 1.9 liter 4 cylinder turbo-diesel direct injection (TDI) engine, used here in the Golf. Also shown: Dodge Ram with Cummins 24 valve diesel; Ford HEUI Powerstroke; and GMC Duramax 6.6 V8 applications.

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Clean Diesels?” You may think we’re joking, but diesel engine manufacturers have been working overtime to clean up the “dirtystinkynoisy” perception of diesels over the last few years; and market acceptance of light duty diesel vehicles is picking up. Fact is, diesel OEs (original equipment manufacturers) in the U.S. and Europe are predicting a diesel “mega-boom.”
Here in the U.S., sporty diesel pickups and SUVs are more and more seen fueling up alongside medium and heavy diesels. Why? Because today’s diesel vehicles are quieter, more powerful and less offensive, thanks to the electronics needed to meet stricter EPA standards.
While petroleum-diesel fuel is not considered an alternate fuel (as is synthetic or bio-based diesel fuel), it is getting cleaner. Dual-fuel diesels are using alternate fuels like natural gas for even lower overall emissions. In Europe, seven out of 10 luxury cars are now diesel powered, and new diesel passenger car sales are reportedly near 40 percent; by 2010 they’ll reach 50 percent.¹
The growing popularity of light diesel trucks in the U.S. is forecasted to continue with diesel powered vans & SUVs. Diesel automobiles are also making a comeback. Second-generation “refined power” diesel engines with greater efficiency and improved overall performance are part of the reason. Diesel engines for light duty hybrid electric vehicles (HEVs) developed both by Ford and DiamlerChrysler for the ill-fated Partnership for a New Generation of Vehicles (PNGV) have achieved upwards of 70 mpg. No doubt engines like these will find their way into production vehicles.

Diesel Fuel Systems

• Diesel fuel injection
• High pressure components
• Diesel fuel
• Diesel fuel characteristics
• Cetane number

Diesel fuel injection

All diesel engines draw air only, past the intake valve into the cylinder. A high-pressure fuel-injection system injects fuel into the cylinder. The amount of fuel injected is varied to suit the load on the engine, and to control engine speed. Intake air volume does not change.
In a basic diesel fuel system, a fuel tank holds the diesel fuel. A lift pump takes fuel from the tank. It keeps the injection pump full of fuel. A sedimenter removes any water, and larger particles in the fuel. A fuel filter removes minute particles. An injection pump delivers fuel under very high pressure to the injectors, along injector pipes. It must send the correct amount of fuel, and it must send it at the correct time in the engine cycle. An injector, at each cylinder, sprays fuel into each combustion chamber. Leak-off pipes take fuel used for cooling, and for lubrication, from the injection pump and injectors back to the tank. They also help to remove air from the system. A governor controls engine speed. And a control lever on the governor is connected to the accelerator pedal.
The basic system is divided into 2 sections. This is the low-pressure side.
The low-pressure side cleans the fuel and delivers it to the high-pressure side, or fuel injection system. Dirt and water will damage a diesel fuel injection system. The highly polished components need a very efficient filtration system to ensure all traces of dirt and water are removed.
The highly-polished finish is achieved by lapping 2 components together to form a matched set. Matched components must not be interchanged after lapping is completed.
The high-pressure side of fuel injection system must raise the pressure of the fuel high enough to open an injector. This allows the fuel to be forced into the combustion chamber at the correct time.