The Humble Mechanic's Guide to Understanding Diesel Fuel Systems

Inside the Engine Compartment: A Journey Through the Fuel System

As we begin our journey through the fuel system, we find ourselves inside the engine compartment. Here, we have a volume pump that's located within the tank and is responsible for moving fuel into the engine. This pump is typically not increasing the pressure but rather relocating it to different parts of the system. From the tank, the fuel moves into the fuel filter housing, where it encounters a metal filter. The purpose of this filter is self-explanatory - it filters the fuel before it's used in the engine.

The Fuel Filter: A Crucial Component

The fuel filter is a crucial component of the diesel fuel system. Its primary function is to clean the fuel by removing impurities and contaminants that could damage the engine. This ensures that the fuel delivered to the engine is clean and free from debris, which is essential for optimal performance.

Electrical Fuel Pumps: A New Era in Diesel Fuel Systems

Not all diesel engines feature electronic fuel pumps, but those that do are a significant improvement over earlier systems. The electronic fuel pump increases the volume of fuel while also providing higher pressure, which allows for more efficient combustion and better engine performance. This is particularly noticeable in newer models of diesel engines.

The Mechanical High-Pressure Fuel Pump: A Marvel of Engineering

One of the most fascinating components of the diesel fuel system is the mechanical high-pressure fuel pump. This pump is driven by the timing belt, just like the camshaft and crankshaft, and is designed to provide a consistent flow of high-pressure fuel to the engine. Inside the pump, we find a rotating cam lobe that presses against a series of pistons, creating a pumping action that squirts fuel out into the system.

The Fuel Pressure: A Critical Component

The mechanical high-pressure fuel pump produces fuel at an incredibly high pressure - around 1200 psi (8 bar), to be exact. This is achieved by converting the rotational energy of the timing belt into kinetic energy, which is then harnessed to drive the pistons and create the pumping action. The increased pressure allows for more efficient combustion, resulting in better engine performance and fuel efficiency.

The Fuel Rail: A Critical Distribution System

Once the high-pressure fuel has been produced, it's distributed out to the injectors through a series of tubes and lines. The fuel rail is an essential component of this system, as it provides a stable and consistent flow of fuel to the injectors. Sensors are located at either end of the fuel rail, monitoring the pressure and flow rates to ensure that the engine receives the precise amount of fuel it needs.

The Fuel Injectors: The Final Stage

Finally, we arrive at the fuel injectors themselves, which are responsible for delivering the pressurized fuel into the cylinder. These injectors use a combination of solenoid valves and fuel pumps to precisely control the flow of fuel, ensuring that the engine receives exactly what it needs. The low-pressure side of the system allows for adjustments to be made in real-time, ensuring optimal performance.

The Magic of Diesel Fuel Injection

So, where do all these components come together? The answer lies in the magic of diesel fuel injection. As the pressurized fuel is delivered into the cylinder, it's ignited by the spark plug, producing a small explosion that drives the piston down and ultimately powers the engine. This process happens repeatedly, with each cycle creating more power and torque than the last.

The End Result: A Powerful Diesel Engine

At the end of the day, our journey through the diesel fuel system has come full circle. From the volume pump to the mechanical high-pressure fuel pump, every component plays a critical role in delivering pressurized fuel into the cylinder. And when it all comes together, the result is a powerful and efficient diesel engine that's capable of delivering impressive performance and torque.

"WEBVTTKind: captionsLanguage: enhello everyone and welcome in this video we're going to be talking about how diesel fuel systems work uh from the tank to the engine and uh you know rather than do my usual stand in front of a whiteboard routine do people watch that website you know surprising people are pretty into whiteboards these days i have one right over there just right on it's not bad looking we didn't include it in the shot you know it's probably uh taking back from the video that it's not in the shot but you know stickers will do perhaps we'll maybe use the cork board we can maybe drop pictures and put some more hot wheels up there while we're filming uh but regardless we're just going to work through the different components and talk about what they do so the first thing uh your fuel goes into a fuel tank so charles tell me a little bit about a fuel tank what is the fuel cell the great thing about fuel components is in the name they tell you exactly what they do so the fuel tank is a tank that holds fuel i know it's crazy okay so where's the fuel going from the fuel tank so once it's in the tank the fuel is pulled up into an electric pump that pump is the delivery pump that delivers volume from inside the tank up into the engine compartment okay so it's not necessarily increasing the pressure it's just moving it this is a volume pump that's inside the tank and then from there where is it going so once we're in the engine compartment we actually go into the fuel filter housing again that does exactly what it says metal filter this fuel filter what does it do it filters the fuel okay yep self-explanatory self-explanatory so it comes in it goes through the filter it goes out and where does it go after it travels through this beautiful filter once we've filtered the fuel we then go to an electronic fuel pump now not all of the diesels are going to have the electronical fuel pump uh that is more of an early generation common rail part okay and that will increase volume what is this out of pressure as well this all these components are out of a generation one common rail volkswagen i don't recall exactly what car they came out of but all these components came out of a car that was mis-fueled so these all had gasoline contamination on them or in them i guess okay so we've got our electronic fuel pump and that's sending fuel to what from the electronic fuel pump we then go to the mechanical high pressure fuel pump the mechanical pump is driven by the timing belt so it's timed just like the camshaft and crankshaft are going to be and it's actually pretty cool you can see inside here uh you've got this cam lobe and so this rotates and as this rotates you've got this right here which is going inside here somewhere like this i'm not that good at it but point is that yeah right am i close enough so anyways ram it in there that cam lobe's in there spinning and that's pressing up against this and as it presses up against this it's pumping this thing back and forth and that's squirting fuel out here so it's like that and then squirting out there right that's what's happening that's exactly right okay you're laughing but that's exactly what it's doing you nailed it okay nailed it yep another uh euphemism we've got going in there so this is squirting out fuel at a higher pressure and then where's that fuel going once we leave the high pressure pump we actually switch from mostly rubber lines to a hard material line because of the increased pressure we're running at roughly 800 bar depending on which exact generation 800 bar times 15 for psi that's about 1200 psi someone will nitpick that is an estimated estimated fuel pressure correct that's what the engineer would write down uh for target esc.12 yeah okay exactly that's well to be fair that's so it's going from this to this correct this is the fuel rail we have sensors on each end of the fuel rail high pressure fuel comes in here then it's distributed out to the injectors well yeah i mean there's a line in between but yeah i'm not that poor at uh connecting threads to threads but anyways uh so the fuel comes in here and then where's it going from here from the rail to the delivery lines for the injectors then we go into the fuel injectors that i have right here i'm gonna hold this one thank you now this see this does screw onto that works perfectly good at that okay so these are fuel injectors and what do these these inject fuel into the cylinder this is a direct injection fuel system so it goes straight into the cylinder which is actually pretty common on diesel engines now is this going to be remain at that 1200 psi is that the pressure that it's injected at or 100 bar roughly and that varies uh depending on the engine and things like that right okay great we also have a low pressure control side without the low pressure side which is this line here uh the injector actually won't work oh interesting so after the fuel goes into the engine what happens that's where all the magic happens and then you are powered and you're on your way yeah then coming out of the tailpipe we have up to 40 times more knox emissions oh wait that's that's for a different video oh this is uh this is a volkswagen system so yeah cheating comes out of the table actually cheating starts at fuel fill up we like to make sure just you know cheap the whole way you might as well you're gonna go for it go big yeah forget the urea injection just go for it that stuff costs a lot that's right you don't want cost you want power we want we want power and torque okay cool i think that sums up our fuel system the most important thing you have to do at this point is subscribe to charles's channel the humble mechanic i'll include links all over the place in the video description things like that and thank you charles for walking me through this system yeah jason thanks for coming by man appreciate ithello everyone and welcome in this video we're going to be talking about how diesel fuel systems work uh from the tank to the engine and uh you know rather than do my usual stand in front of a whiteboard routine do people watch that website you know surprising people are pretty into whiteboards these days i have one right over there just right on it's not bad looking we didn't include it in the shot you know it's probably uh taking back from the video that it's not in the shot but you know stickers will do perhaps we'll maybe use the cork board we can maybe drop pictures and put some more hot wheels up there while we're filming uh but regardless we're just going to work through the different components and talk about what they do so the first thing uh your fuel goes into a fuel tank so charles tell me a little bit about a fuel tank what is the fuel cell the great thing about fuel components is in the name they tell you exactly what they do so the fuel tank is a tank that holds fuel i know it's crazy okay so where's the fuel going from the fuel tank so once it's in the tank the fuel is pulled up into an electric pump that pump is the delivery pump that delivers volume from inside the tank up into the engine compartment okay so it's not necessarily increasing the pressure it's just moving it this is a volume pump that's inside the tank and then from there where is it going so once we're in the engine compartment we actually go into the fuel filter housing again that does exactly what it says metal filter this fuel filter what does it do it filters the fuel okay yep self-explanatory self-explanatory so it comes in it goes through the filter it goes out and where does it go after it travels through this beautiful filter once we've filtered the fuel we then go to an electronic fuel pump now not all of the diesels are going to have the electronical fuel pump uh that is more of an early generation common rail part okay and that will increase volume what is this out of pressure as well this all these components are out of a generation one common rail volkswagen i don't recall exactly what car they came out of but all these components came out of a car that was mis-fueled so these all had gasoline contamination on them or in them i guess okay so we've got our electronic fuel pump and that's sending fuel to what from the electronic fuel pump we then go to the mechanical high pressure fuel pump the mechanical pump is driven by the timing belt so it's timed just like the camshaft and crankshaft are going to be and it's actually pretty cool you can see inside here uh you've got this cam lobe and so this rotates and as this rotates you've got this right here which is going inside here somewhere like this i'm not that good at it but point is that yeah right am i close enough so anyways ram it in there that cam lobe's in there spinning and that's pressing up against this and as it presses up against this it's pumping this thing back and forth and that's squirting fuel out here so it's like that and then squirting out there right that's what's happening that's exactly right okay you're laughing but that's exactly what it's doing you nailed it okay nailed it yep another uh euphemism we've got going in there so this is squirting out fuel at a higher pressure and then where's that fuel going once we leave the high pressure pump we actually switch from mostly rubber lines to a hard material line because of the increased pressure we're running at roughly 800 bar depending on which exact generation 800 bar times 15 for psi that's about 1200 psi someone will nitpick that is an estimated estimated fuel pressure correct that's what the engineer would write down uh for target esc.12 yeah okay exactly that's well to be fair that's so it's going from this to this correct this is the fuel rail we have sensors on each end of the fuel rail high pressure fuel comes in here then it's distributed out to the injectors well yeah i mean there's a line in between but yeah i'm not that poor at uh connecting threads to threads but anyways uh so the fuel comes in here and then where's it going from here from the rail to the delivery lines for the injectors then we go into the fuel injectors that i have right here i'm gonna hold this one thank you now this see this does screw onto that works perfectly good at that okay so these are fuel injectors and what do these these inject fuel into the cylinder this is a direct injection fuel system so it goes straight into the cylinder which is actually pretty common on diesel engines now is this going to be remain at that 1200 psi is that the pressure that it's injected at or 100 bar roughly and that varies uh depending on the engine and things like that right okay great we also have a low pressure control side without the low pressure side which is this line here uh the injector actually won't work oh interesting so after the fuel goes into the engine what happens that's where all the magic happens and then you are powered and you're on your way yeah then coming out of the tailpipe we have up to 40 times more knox emissions oh wait that's that's for a different video oh this is uh this is a volkswagen system so yeah cheating comes out of the table actually cheating starts at fuel fill up we like to make sure just you know cheap the whole way you might as well you're gonna go for it go big yeah forget the urea injection just go for it that stuff costs a lot that's right you don't want cost you want power we want we want power and torque okay cool i think that sums up our fuel system the most important thing you have to do at this point is subscribe to charles's channel the humble mechanic i'll include links all over the place in the video description things like that and thank you charles for walking me through this system yeah jason thanks for coming by man appreciate it\n"