Marine Diesel
Who invented the Diesel engine?
The first diesel engine was designed a build by Rudolf Diesel in 1893. It was the first engine that proved fuel could be ignited with high compression alone. This engine consisted of a single 3meter cylinder and flywheel at the bottom. After making improvements this engine was put into production in 1897 and was used to power Boats, Cars, Trucks, Power plants etc.
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| One cylinder diesel 1906 |
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| Yamaha marine diesel |
How does a Diesel pump work?
The diesel pump runs off the engine via the cambelt. The rotating force of the engine turns a Cam shaft, as the camshaft turns its pushes on valves that draw in and compress the diesel. As the diesel is compressed it passes through short pipinng to the Injectors. As pressure overcomes the injector spring diesel is squirted into the cylinder. As engine RPM increases so does the pump speed.
What pressure would you get from a Diesel pump?You can expect a pressure around 15000psi/1000bar.
Why do you need to time the pump?
You need to time the diesel pump so that the diesel is squirted through the injector just before the cylinder reaches TDC.
How do you time the pump & with what equipment?
To time the diesel injection pump you will need a diesel timing gauge and a few spanners. This gauge is usualy fitted to the end of the pump and is used to measure the injection timing, 1 degree before TDC.
What is the purpose of a Glow plug?
Glow plugs are little electric heaters that are fitted to the small combustion chambers in an Indirect injection diesel. The glow plug inceases the temperature of the air being compressed, making up for the heat lost to the cold parts of the engine. These plugs are connected to the ignition and operate during startup.
How do you test the circut?
Using a multileter we can test the resistance within the glow plug. Resistance should be about 1 ohm, with a tolerance about 0.2 ohm higher/lower. Anything higher or lower would suggest replacement of all glow plugs within the circut.
-Glow plugs can be tested by attaching a ampmeter in series within the circut. You should get a reading of about ten amps per glow plug. If the reading is less than this it would suggest a faulty glow plug.
-You test the glow plug by applying power directly to the plug. It should immediatly start to heat up, take note when the plug heats up as is should heat from the end back. If this is not the case it would suggest a fault.
-Glow plugs can be tested by attaching a ampmeter in series within the circut. You should get a reading of about ten amps per glow plug. If the reading is less than this it would suggest a faulty glow plug.
-You test the glow plug by applying power directly to the plug. It should immediatly start to heat up, take note when the plug heats up as is should heat from the end back. If this is not the case it would suggest a fault.
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| Note the secondary lift pump and manual primer pump. |
Why do you need a lift pump on a Diesel engine?
A lift pump is a mechanical pump that is used to get fuel from the tank to the in-line pressure pump. This pump can be found on the side of the in-line pump. A diaphragm pump is operated by a Cam lobe in the In-line pump. There is also a hand operated primer pump.
Why do you need an Electronic fuel shut-off solonoid?
Because the pump and injectors are both mechanicaly operated, as long as there is fuel to be pumped to the injectors an into the engine, the engine will continue to operate. For this reason you need an electronic shut-off solonoid to shut down the fuel supply to the engine. This is usualy hooked up through the ignition. As the ignition comes on voltage passes through the solonoid opening the valve, allowing fuel to flow. When the ignition is switched off the voltage stops and the valve closes, stopping the fuel supply to the engine.
What is the knock sensor for & where is it situated?
The knock sensor is screwed into the crank case. It is designed to pickup vibration from the engine during combustion. Vibrations are sent out from the cylinder across the block as combustion occurs. These vibrations vary depending on when ignition occurs during the stroke, how much fuel is being burn, what type of fuel is burn eg. octanne level. These vibrations allow the ECU to pick up on problems such as Pre-ignition, Detonation, Pinking.
How do Diesel injectors work?
Diesel injectors work using pressure created by the pressure pump. Diesel is pumped into the injector from the pump, it fills into the needle chamber until it forces the needle off its seat. Once the needle raises out of its seat it allows the diesel to squirt out under emence pressure into the compressed air. A pressure spring within behind the needle forces it back on its seat.
Why do you need to bleed a Diesel engine after replacing a fuel filter or removing the pump?
It is important that you bleed the diesel engine so that an air block does not occur. An air block can restrict movement of fuel and can also damage to the engine when under pressure.
A diesel engine is bled by unscrewing bleed srews situated around the engine block.
How does a turbo work?
A turbo works using the force of the exhaust exiting the engine. A turbine is mounted on one end for the shaft and a compressor wheel on the other. This is housed so that the turbine is pushed by the exhaust, this then causes the compressor wheel to spinn drawing air in and compressing it against the intake manifold.
Why do we need a turbo fitted to a diesel engine?
We fit a turbo to a diesel engine because this increases the amount of air that enters the cylinder. Because we have more air in the cylinder we are able to burn more fuel. Resulting in increase volumetric efficiency and higher power output.
What is a supercharger?
A supercharger is very similar to a turbo, they both compress air to increase air intake. However a supercharger runs off a belt, gear or chain.
A supercharger is very similar to a turbo, they both compress air to increase air intake. However a supercharger runs off a belt, gear or chain.
What is the difference between a turbo and a superchager?
A Supercharger is run off a Belt, Gear or Chain. A turbo is run using the pressure from exhaust gases.
A Supercharger is run off a Belt, Gear or Chain. A turbo is run using the pressure from exhaust gases.
Why do we need an after-cooler fitted to a diesel engine?
We have this fitted to cool the air that is compressed, either by the superchager or turbo. The air is compressed into a heat exchange device before entering the intake system. This device will be ether air-to-air or air-to-liquid.
Indirect injection - Indirect injection is when the diesel fuel is injected into a pre-combustion chamber to ignite before fully burning and acting on the piston. This small chamber is located in the cyclinder head, the glow plug and injector both screw into this chamber.
Direct Injection - Direct injection refers to a diesel engine that injects fuel directly into the combustion chamber above the piston. This type of system does not allow use of glow plugs.
What is the purpose of a Governor?
The govenor shaft and flyweight are situated on one end of the pump cam. It is desgined to spin slightly faster than engine speed using cetrifugal force created as the flyweights extend. As the flyweights rotate they move the govenor sleeve along its shaft to push on the lever. Movement of the lever will move the pump plunger and vary the amount of fuel.
What is the difference between Diesel & Diesel common rail?
The difference is that a common rail system is electronicaly controlled an uses a common fuel rail instead of an individual fuel line to each injector. A common rail system has high pressure pump which provides fuel from the tank to the 'common rail' ( A fuel rail connected to the injectors). The common rail has a pressure release valve on one end to regulate fuel pressure to the injectors. The ECU calculates cam & crank position and air intake and instructs the injectors to deliver the required amont of fuel. pressure about 2000bar/29000psi.
Reference
Very good effort again, well researched.
ReplyDeletegreat job
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