The document provides information on diesel engines and their fuel injection systems. It discusses the history and invention of the diesel engine by Rudolf Diesel in the late 19th century. It then describes the basic operation and components of diesel engines, focusing on key differences from gasoline engines like ignition via heat of compression rather than sparks. The rest of the document details diesel engine fuel systems, servicing procedures, and the two main types of fuel injection pumps - inline plunger pumps and rotary distributor pumps.
The document provides information on diesel engines and their fuel injection systems. It discusses the history and invention of the diesel engine by Rudolf Diesel in the late 19th century. It then describes the basic operation and components of diesel engines, focusing on key differences from gasoline engines like ignition via heat of compression rather than sparks. The rest of the document details diesel engine fuel systems, servicing procedures, and the two main types of fuel injection pumps - inline plunger pumps and rotary distributor pumps.
The document provides information on diesel engines and their fuel injection systems. It discusses the history and invention of the diesel engine by Rudolf Diesel in the late 19th century. It then describes the basic operation and components of diesel engines, focusing on key differences from gasoline engines like ignition via heat of compression rather than sparks. The rest of the document details diesel engine fuel systems, servicing procedures, and the two main types of fuel injection pumps - inline plunger pumps and rotary distributor pumps.
The document provides information on diesel engines and their fuel injection systems. It discusses the history and invention of the diesel engine by Rudolf Diesel in the late 19th century. It then describes the basic operation and components of diesel engines, focusing on key differences from gasoline engines like ignition via heat of compression rather than sparks. The rest of the document details diesel engine fuel systems, servicing procedures, and the two main types of fuel injection pumps - inline plunger pumps and rotary distributor pumps.
The diesel engine is a type of internal combustion engine that was
invented by Rudolf Diesel. He received a patent for the diesel engine in 1892. The primary goal was to create an efficient alternative to the gasoline engine.
Both gasoline engines and diesel engines work by creating a controlled explosion in a sealed piston chamber. The small explosion rapidly moves the piston, which in turn rotates the output shaft. In a gasoline engine, a mixture of fuel and air are injected into the chamber and then ignited with a spark created by a spark plug. A diesel engine, on the other hand, does not rely on a spark plug to ignite the mixture.
Fuel is forced into the chamber and the high pressure generates enough heat to ignite the fuel/air mixture. Some diesel engines rely on a glow plug to heat the chamber to minimize the amount of pressure required for the engine to turn. Without such an added heat source, the pressure required to achieve ignition (especially when the engine is cold) would be prohibitively high.
Diesel engines require diesel fuel for the combustion process to function properly. Diesel fuel is cheaper than regular gasoline because less refining is required. In addition, diesel engines are more efficient and therefore diesel cars get better mileage than their gasoline counterparts.
Diesel engines are similar to spark ignition engines in construction. Both have pistons, piston rings, moving up and down in cylinders. Both burn fuel in combustion chambers in the upper part of the cylinders. The high pressure produced by the burning fuel pushes the pistons down. This rotates the crankshaft and the rotary motion is carried through shafts and gears to the drive wheels.
The diesel engine has the following characteristics:
1. No throttle valve (except some engines with the pneumatic governor).
2. Compresses air only on the compression stroke. 3. Heat of compression ignites fuel as it sprays into the engine cylinders. 4. Has a high compression ratio of 16:1 to 22:1. 5. Controls engine power and speed only by the amount of fuel sprayed into the cylinders. More fuel equals more power. 6. Have glow plugs or an electric intake-manifold heater to make starting easier. Figure 1 shows the four pistons strokes in a four-stroke cycle diesel engine.
1. INTAKE STROKE. The diesel engine
takes in air alone. No throttle valve impedes the airflow. 2. COMPRESSION STROKE. The upward- moving piston compresses air alone. 3. POWER STROKE. A light oil called diesel fuel is sprayed (injected) into the compressed and hot air. The heat of compression ignites the fuel. 4. EXHAUST STROKE. The exhaust stroke is the same for both engines. The exhaust valve opens and the burned gases flow out as the piston moves up the cylinder.
Diesel Engine Tune Up
Diesel Engine Fuel System
• Deliver the right amount of fuel to meet the operating requirements.
• Time the opening of the injection nozzles so the fuel enters the engine cylinders at the proper instant. As engine speed increases, fuel injection must start earlier. This gives the fuel enough time to burn and produce pressure on the pistons. Without the advance action, the pistons would be over TDC and moving down before the fuel fully ignites. This wastes fuel and power. • Deliver the fuel to the cylinders under high pressure. Injection pressure must be high enough to overcome the high compression pressure in the diesel engine. At the end of the compression stroke, compression pressure may be 500 psi [3447 kPa] or higher.
Servicing Diesel Engines and Fuel Systems
Basic servicing procedures on diesel engines are similar to those for spark-ignition engines. The transfer pump or fuel-supply pump is similar to the mechanical fuel pump used in carbureted spark-ignition engines. Air in the fuel-return line of a diesel engine can be caused by a leak in the line between the pump and the fuel tank. This is the vacuum side of the pump and will draw in air. Servicing Injection Lines and Fittings
Injection lines in diesel-engine fuel-injection systems are also called high-pressure fuel lines, injection tubes and injection pipes. They carry fuel under high pressure from the injection pump to the injection nozzles. The image above shows the various shapes of injection lines between the injection pump and the nozzles. When the line requires replacement, always install the line specified by the vehicle manufacturer. Variation from the specified length and internal diameter may cause engine trouble. New lines are preformed. Avoid twisting or bending them out of shape during installation.
Servicing Fuel Filters
The fuel filter is located in the low-pressure fuel line from the fuel tank to the injection pump. The filter element is similar to filters used in engine lubricating systems.
The fuel must pass through the fuel element which traps any dirt particles. Replace the filter periodically as recommended by the manufacturer.
VOLATILITY | VISCOSITY
VOLATILITY
This is a measure of how easily a liquid evaporates. Gasoline vaporizes easily. It has a high volatility. Diesel fuel has low volatility. It boils at a temperature of about 700ºF [371ºC]. There are two grades of diesel fuel for automotive diesel engines, number 1 diesel and number 2 diesel. Number 1 diesel is more volatile. It is used when temperatures are very low. Number 2 diesel is the recommended fuel in most automotive diesel engines for most driving conditions. The less volatile fuel usually has a higher heating value. When it burns, more energy is available than from a fuel with higher volatility.
VISCOSITY
This refers to a liquid’s resistance to flow. The lower the viscosity, the more easily the liquid flows. Diesel fuel must have a relatively low viscosity. It must flow through the fuel-system lines and spray into the engine cylinders with little resistance. Oil with high viscosity will not break into fine particles when sprayed.
Lesson 1: Diesel Fuel Injection Pump
Automotive diesel engines use two types of fuel injection pumps. One is an inline cam- operated pump. It has a plunger for each engine cylinder. The other is a rotary, distributor- type pump. One or two plungers supply the fuel for all injection nozzles.
Inline – Plunger Injection Pump
Figure F0 shows an inline-plunger pump on a six-cylinder diesel engine. The pump has a barrel-and-plunger assembly for each cylinder. An injection line or tube connects each barrel-and-plunger assembly to an injection nozzle.
The construction of a barrel-and-plunger assembly is shown in Figure F1. Low-pressure fuel
from the fuel supply pump flows through the inlet port into the space above the plunger.
The plunger has a roller that rides on a cam on the camshaft. This is like the roller tappets used in some engine valve trains. When the cam lobe comes up under the plunger, the lobe raises the plunger. This applies high pressure on the fuel trapped above the plunger.
The fuel is forced through the tube to the injection nozzle in the cylinder where the piston Is reaching TDC on the compression stroke. The fuel sprays out and ignites from the heat of the compression. The amount of fuel injected is varied by varying the effective stroke of the plunger.
This is shown in Figure F1. The control rod connects by linkage through the governor to the accelerator pedal. As the driver depresses the pedal, the linkage causes the control rod to move. This turns the plunger in its barrel. The plunger has a groove and an inclined helix machined into it
Turning the plunger for more fuel rotates the helix so a wider section faces the inlet port. This closes the port for a longer time, increasing the effective stroke of the plunger. Fuel delivery begins when the top edge of the plunger closes off the inlet port. Fuel delivery stops when the helix opens the inlet port.
The fuel-injection pump has a speed-advance mechanism. It advances the time of injection as engine speed increases. This gives the fuel the necessary time to ignite, burn and produce high pressure. Without injection advance, weak power strokes result at higher engine speeds.
Rotary Distributor Injection Pump
The distributor has two controls. One controls timing and the other controls the amount of fuel injected. The timing device connects to the internal cam ring. This is the cam on which the rollers roll. As engine speed increases, the cam ring moves ahead. This causes the two plungers to move out and in earlier, advancing the start of injection. At the same time, the internal governor regulates the amount of fuel delivered to the cylinders.
removing the bolts. Pull out the injection pump from the cover.
Set the injection timing
Remove the timing mark cover.
Find the marks on the idler gear and the
injection pump gear.
Return the injection pump and align the
timing marks of the injection pump gear and the idler gear.
Inspect the position of the injection pump
gear timing mark. It must be between the idler gear timing marks.
Install the bolts holding the injection pump
and tighten. Return the timing mark cover.
Lesson 1: Timing Device
The timing device usually consists of an aluminum casting with mounting flanges at both ends. A bore in the housing guides and supports the spider assembly. A timing opening, with a cover, is located in the top of the housing and is used to observe the position of the timing pointer in relation to the timing mark on the timing device hub during injection pump timing procedures.
The timing device hub, with external left-hand helical spines for engaging the internal helical spines of the sliding gear, has a tapered bore and keyway. The hub is secured to the camshaft extension by a woodruff key, nut, and setscrew. The hub is usually counter bored to receive the timing device springs. The springs oppose the flyweight forces of the weight and spider assembly.
The weight and spider assembly has external right-hand helical spines which mesh with the internal helical spines of the sliding gear. The splinted end is machined to receive the end play spacer. Three flyweights are pinned to a flange adjacent to the splints. The weight and spider thrust plate, located between the flange and the timing device housing, carries the back thrust of the flyweights and prevents housing wear.
Operation
• As the engine rotates the weight and spider assembly, centrifugal force opens the flyweights from their collapsed position against the force of the three timing device springs. • As the flyweights swing out, the sliding gear isforced toward the timing device hub. • The longitudinal movement of the sliding gear on its helical splint causes a slight change in the rotational relationship of the injection pump to the engine, causing injection to begin slightly earlier in the power stroke.
Lesson 2: Timing the Fuel Injection Pump
Timing the Fuel Injection Pump
Note: Unless major repair work is done on the engine, timing should not be required.
Four cylinder firing order - 1 - 3 - 4 - 2
Procedure: 1. Remove fuel lines from injector pump fittings on injector pump. 2. Pull the decompression lever so that it will remain in the decompression position. No decompression lever on Model-12 3. Open throttle fully. 4. Energize the electric fuel pump and turn engine over with starter to ensure that fuel is coming out of each injector pump opening. Have clean rags around opening to soak up fuel. 5. Wipe off any fuel on injector pump body and the top of each injector opening. 6. Turn crankshaft over by hand, being careful not to damage splint on end of crankshaft. Engine rotation will be clockwise. STOP IMMEDIATELY at the first sign of fuel movement in the injector pump fuel fitting, for whichever injector pump is being checked. (No. 1 injector pump is the closest to the V-belt end of the engine). 7. Remove the cover from flywheel timing mark inspection hold located inside of left engine mount. 8. Check alignment of mark on flywheel with the timing pointer on the wall of the inspection hole. The 1-Fl mark on the flywheel represents fuel injection of No. 1 cylinder. 2-Fl represents No. 2 cylinder, etc. 9. If timing pointer and the flywheel marking 1-Fl is aligned, then No. 1 cylinder is properly timed for fuel injection and should require no adjustment. The same will be true for No. 2, No. 3 and No. 4 cylinders if the above steps are followed. 10. In order to determine if timing is off, or if the injection pump is faulty, it is necessary to recheck the timing for each cylinder two or three times. 11. If there are variations in repeatability in the alignment of pointer and timing mark, a faulty fuel injector pump may be suspected. 12. If timing marks repeat to same location but are off 3/16" or more above or below the pointer, this indicates that the engine must be retimed. If alignment of the timing mark is not within 3/16" above or below the pointer, the above steps must be taken to time the engine. If the timing is found to be satisfactory, then reconnect all fuel lines and fittings and tighten. The fuel system must be bled before the engine will operate properly.
Lesson 3: Checking the Injection Nozzle
Checking the Injection Nozzle
Note: Never remove an injection nozzle from the engine except for service or replacement.
The following indicate injection-nozzle trouble:
• One or more cylinder knocking.
• Loss of power.
• Smoky black exhaust.
• Engine overheating.
• Excessive fuel consumption.
Procedure: 1. One way to check injection nozzles is to run the engine at fast idle. 2. Loosen the connector at each nozzle in turn, one at a time. 3. Wrap a cloth around the connection before you loosen it to keep fuel from spurting out. If loosening the connector causes engine speed to drop, the nozzle is probably working normally. If the engine speed remains the same, the nozzle is not working properly. Clogged holes are preventing fuel delivery or causing an improper spray pattern. Some manufacturers recommend a spray test of the detached injection nozzle. This requires a nozzle tester, which is a special hydraulic pump and pressure gauge. 4. Attach the nozzle and apply pressure. The fuel should spray in an acceptable pattern when the specified pressure is reached. 5. Releasing the pressure should stop the spray abruptly without any drip from the nozzle.
Caution: Direct the spray from the nozzle into a suitable container. Do not allow the spray to hit your skin. The pressure is high enough to force fuel oil through the skin. You can be seriously injured because the oil could cause an infection. If the engine misses at all speeds and produces a puff of exhaust smoke each time it misfires, an injection nozzle is probably sticking open. The nozzle can be disassembled and cleaned. Somemanufacturers recommend replacing a faulty nozzle.
Caution: If you disassemble a nozzle, do not damage the tip or enlarge the holes. This can cause leakage and other troubles.
Lesson 1: Bleeding the Fuel System
Bleeding the Fuel System
It is necessary to bleed the fuel system to achieve a steady air free flow of fuel if any of the following has occurred:
• Running out of fuel.
• If fuel shut off valve is left closed and engine runs out of fuel. • Replacing fuel filter. • Fuel injector nozzle or injector pump repair. • After repairing or replacing any fuel line. • Before putting engine back into service in the spring, if fuel system has been drained. • Replacement of electric or mechanical fuel pump. • Any time air is permitted to enter the fuel system.
