A diesel engine is an IC engine, the primary purpose of which is to use “Compression Ignition” to convert energy into work just like a heat engine. It uses pistons for compressing a mixture of air that contains oxygen with diesel fuel. The piston is also attached to a shaft and moves back and forth to give the required work. For more detailed info about diesel pumps, please refer to What is a diesel pump
Some of the components of a diesel engine, along with their details, are given below.
This system contains a lift pump, fuel injection pump, fuel pipes, and injectors. It also includes some water separators and fuel filters in order to not let the bad-quality fuel damage the engine which will cost you a hefty amount later.
This system helps the diesel engine run smoothly and avoids wear and tear of the parts that are caused by friction. As suggested by its name, it uses oil for lubrication. And since the oil must be clean from contaminants, oil filters are also available.
Every engine needs a coolant in order for the mixture in it to not get overheated because this will ultimately affect the entire system. And this coolant works under the cooling system. Usually, a mixture of glycol, distilled water, and some additives is used to prevent corrosion. Just like the above-mentioned systems, this one also contains a filter for cleaning the coolant. There is a coolant pump available as well for pushing the coolant around. When it gets hot, a heat exchanger cools it.
Waste gases are used at times in industries, and therefore storage tanks are available for them, which we usually call reboilers. But sometimes, the gases are toxic, and they must be thrown away, but not in the environment, which is why exhaust systems are available. A muffler is also installed to reduce noise while throwing the waste gas away. Also, such a system must contain filters to avoid polluting the environment, or else the NOx and SOx will not even let the people breathe. That’s also why chimneys are installed at a more significant height.
Some diesel engines have turbochargers as well for compressing the combustion air. This makes the engine power and ultimately, its efficiency increase.
Now that we’ve got an idea of what a diesel engine is and how its works, let’s take a look at which kind of pump is used in diesel engines.
Every diesel engine contains a fuel injection system, the heart of which is a Fuel Injection Pump. It has a crucial role to play in letting the engine work properly. The primary purpose of it is to pump the fuel (to injectors). It also helps in distributing and metering fuel supply to the injectors. Another function it performs is pumping the correct fuel quantity at a suitable time, which makes the engine work efficiently. And if you are using a multicylinder pump, it will also help distribute the pump to all those cylinders. This part combined with a question, how does a diesel pump work, which you can find in What is a diesel pump
In some vehicles, this pump only helps pressurize the fuel because fuel distribution is done using electric injectors. A crankshaft is mainly used to drive this pump.
Let’s take a look at some of the functions that a Fuel Injection Pump Performs.
The ultimate goal of a pump is to increase the fuel pressure, which is what this pump does. But it can pump the fuel at higher pressure after drawing it from the fuel tank. However, for electronic systems, it only pressurizes the fuel line. This pump also controls the fuel needed to be supplied to injectors.
Fuel distribution to the cylinders is another function a fuel injection pump performs. If you take “Inline Fuel Injection” into account, you will need a fuel barrel and a plunger to supply the fuel.
The injectors tend to bear a higher temperature, so they must be cooled to avoid overheating, or else the system may stop working. So, this is possible if you pump low-temperature fuel in the injector. So, you can use the pump for cooling purposes also. You can do one more thing in this regard, just circulate a coolant around the injectors and cool them. But the problem is, you will have to spend an extra amount on that.
So, the easy way is to pump the fuel at a temperature lesser than usual to cool it, and the engine will also not stop working. This may affect the efficiency of the system because the higher the temperature, the higher the efficiency in such systems.
Fuel Injection Pump is not directly used in diesel engines, rather any of its types are used. Here are some of the types of it:
Let’s see the details of each of them.
This pump, as mentioned earlier, uses a fuel barrel and a plunger separately for pumping the fuel. It arranges all the injectors and plungers in one line, and their number is also the same. Some of its components include a plunger, barrel, inlet, and outlet valve. The crankshaft helps reciprocate the plunger by taking power from the engine itself.
If the plunger is moving downwards, that means the barrel is sucking the fuel through the inlet valve. And when it moves upward, it puts pressure on the fuel inside the barrel. This helps in opening the outlet valve, resulting in fuel going out. In most cases, fuel comes out in the form of exhaust gases, but if some part of it is unburnt, that will also go out with flue gases, and you cannot recover that.
The distributor pump, as suggested by the name, uses a rotary distributor to distribute fuel. Its main components include a rotor, stator, and two plungers. The rotor has a discharge passage and a few suction passages, all of them at different elevations.
The stator has one suction passage and multiple discharge passages, and this number is the same as the number of injectors. When suction passages of both stator and rotor align, the plungers start moving away from one another, and fuel enters the control passage.
When discharge passages align, the plungers come close to each other, and the fuel in the control passage enters the discharge ports. That's how the rotor supplies the fuel to all the injectors using the motion of plungers.
This pump, unlike other types, doesn’t distribute the fuel. Instead, it helps maintain pressure on fuel lines. That is also the reason why it is used in electronic systems.
Certain situations will give you an idea about when a fuel pump used in a diesel engine becomes faulty. For more, you may want to check out Can I drive a bad fuel pump, How much does it cost to replace a fuel pump in a car, and What is a fuel pump control module
The unwanted noise coming from the engine is mainly because of the improper injection of the fuel. You will notice it only when driving the car at a higher speed. You may also hear a noise coming from the fuel tank because of insufficient fuel amount in the tank. This doesn’t let the pump suck the fuel; ultimately, the engine doesn’t work as efficiently as it should.
The fuel pump sometimes provides insufficient fuel for combustion when you load a vehicle. Thus, the engine doesn’t generate as much power, because of which it doesn’t work efficiently.
Also, you may have noticed that the fuel pump doesn’t pressurize the fuel line ideally because the engine doesn’t start. Or it starts and then stops again, this is also an alarming situation, and you must check the pump as soon as possible.
The diesel engine doesn’t work well enough under two conditions: when the fuel supply to the injectors is insufficient, and when the pump supplies excessive fuel. So this leads to improper combustion, as a result of which smoky exhaust comes out, and the efficiency of the engine also drops. So, you must check the quantity of fuel supplied to the injectors for the system to work according to your requirements.
Diesel engines use a Fuel Injection Pump that makes them work well and plays a vital role in increasing the system's efficiency. But if it isn’t working correctly, the entire system will stop. So, it is better to keep a check and balance on the system to make it work better. Or else you will have to pay a hefty amount for repairing the system. Or you may need to replace it, which isn’t what you want.