VAG TDI Engine Technical Education

volkswagen has a strong history of producing efficient yet powerful diesel engines however the demands to improve emissions performance fuel economy and noise levels are constantly growing the key factors for meeting these requirements are better mixture control and improved fuel atomization both requirements call for an efficient direct injection system capable of producing extremely high injection pressures whilst at the same time precisely controlling the timing and the volume of fuel delivered into the cylinders back in 1905 rudolph diesel had the idea of combining the fuel pump and the injector into one unit this removes the necessity for high pressure connecting pipes between the injection pump and the injectors thereby allowing the injection pressures to be increased however it wasn't until the nineteen fifties that the idea of pump injection came to fruition when it was introduced into the shipping and haulage industries it became known as mechanical pump injection or the pressure time system mechanical pump injection alone is capable of producing higher fuel pressures which lead to finer atomization however by adding a computer controlled solenoid valve to each injector to precisely regulate the fuel quantity and injection timing volkswagen has created the ultimate pump injection system in the uk the system is known by its german name of pump producer translated it stands for pump and injector meaning that the normally separate components of the diesel injection pump and the injector are combined in a single component if you would like more background information about the reasons for developing pump producer then click on the information button how the diesel fuel is injected into the cylinder and the way it swirls mixes with the air ignites and burns has been the subject of ongoing research ever since rudolf diesel developed and patented the basic diesel engine in 1892. in the volkswagen's turbocharged direct injection or tdi engine the fuel is already injected directly into the cylinder not into a separate chamber as in some other designs hence the name direct injection the function of the turbocharger is simply to force more air into the cylinders which together with additional fuel increases the engine's performance the responsibility of the fuel injectors is to inject the fuel into the cylinder to overcome the pressure of the compressed air within the cylinder the fuel must be injected at an extremely high pressure it's also critical that just the right quantity of fuel is injected and at the right time too much and it produces exhaust smoke insufficient fuel and there is a loss of power similarly other problems arise if the fuel is injected too early or too late therefore the injector is a high precision component the fuel pressure is generated and delivered to the injectors by an equally precisely manufactured component the fuel injection pump the pump is driven by the engine and delivers the exact quantity of fuel to each injector at precisely the right time in most light vehicle applications the injection pump is connected to the fuel injectors by high pressure steel pipes and to a certain extent these pipes have been a limiting factor in improving the diesel engines credentials a critical factor in meeting the increasing demands for reduced exhaust emissions lower fuel consumption and increased performance is better blending of the fuel and air in the cylinder to achieve this it was necessary to improve further the atomization of the fuel as it enters the cylinder this meant greatly increasing the fuel pressure and the connecting high pressure pipes then become somewhat of a limiting factor the solution combine the injector with the fuel injection pump and dispense with the pipes altogether the pump producer system is just that each cylinder has its own pump injection unit the pumperduser unit which is a fuel injector and injection pump combined the high pressure pipes are the submitted and consequently fuel can be injected at a pressure approximately ten times greater than that of a conventional diesel injection system each pump injector unit includes an electronically operated control valve to regulate precisely the time and the duration for which the fuel is injected the control valve is activated by an electronic control unit which also takes care of the entire engine management the ingenious pump producer technology offers many benefits to the customer over conventional diesel injection systems for example pumped user engines develop more power and torque enabling smooth and flexible performance they are exceptionally economical and minimize harmful exhaust emissions the system is suitable for a variety of engine sizes and is relatively quiet in operation and of course no high pressure pipes are required when you are ready to answer some questions click on the forward arrow the pumped user fuel delivery system is completely different to previous systems it has a submerged electric lift pump in the fuel tank fuel filter non-return valve mechanical fuel pump with limiting valve supply line return line pressure regulating valve with bypass temperature sensor and a fuel cooler the function of the submerged electric pump is to lift fuel from the tank and deliver it via the fuel filter and non-return valve to the main mechanical fuel pump the non-return valve prevents fuel from returning to the tank whilst the engine is stationary the mechanical fuel pump is generally of the blocking vein cell type it's located at the end of the cylinder head directly behind the vacuum pump the camshaft drives both pumps simultaneously note however that on the two liter tdi engines the pump is of the gear type from the pump the fuel is directed via the supply line to the injectors the pump also includes a pressure limiting valve that opens should the supply line pressure exceed a set value the exact pressure varies depending upon the engine version excess fuel from the injectors returns to the tank via a pressure regulating valve within the pump the valve maintains a constant return line pressure of about one bar note also the bypass channel which acts to bleed air from the system should the vehicle run out of fuel from the regulating valve returning fuel then flows to the temperature sensor and then onto the cooler before eventually arriving back at the tank the fuel cooler plays an important role in the system as without it the high fuel temperatures created by the sudden pressurization within the pump injectors could damage certain components and may affect the volumetric efficiency of the engine the fuel cooler is a straightforward air heat exchanger which is located beneath the car now explore our fuel system graphic by moving your mouse over the components when you are ready to answer some questions click on the forward arrow as its name implies is simply an injector and pump combined in one unit with this system each cylinder has its own dedicated pump injector unit the engine's camshaft operates the plunger type pump injectors via additional camshaft lobes and roller rocker arms the pump operation is simple as the camshaft rotates the rocker arm forces the plunger downwards compressing the fuel and the extremely fine atomized fuel is delivered directly into the cylinder good mixture formation is a prerequisite for efficient combustion therefore the precise quantity of fuel must be injected at a high pressure and at the correct time furthermore to help reduce noise or diesel knock which is caused by the sudden increase in combustion pressure it's best for the fuel to be injected progressively in stages before we move on to a detailed explanation of the injection process it's a good idea to make yourself familiar with the injector and pump unit move your mouse over the graphic to reveal the names of the components when you're finished click on the forward arrow to continue the first stage injects only a small quantity of fuel and is known as the pre-injection cycle this pre-injection reduces the sudden rise in combustion pressure thus helping to reduce knock the second injection stage is called the main injection cycle and delivers the principal charge a solenoid valve controlled by the engine control unit determines both the timing and the duration of the injected fuel the injection cycle starts with the pumping action and the subsequent filling of the high pressure chamber as the camshaft lobe rotates the pump piston is pushed upwards by the injector spring because the solenoid valve is open fuel under supply line pressure flows into the chamber as the cam rotates further the pump piston is forced downwards displacing the fuel from the high pressure chamber back into the supply line at the correct moment the ecu activates the solenoid closing off the fuels exit to the supply line thus fuel remaining in the chamber becomes pressurized and when it reaches 180 bar the injector needle lifts and the first stage of fuel injection commences this pre-injection cycle soon ends this is because the increasing chamber pressure forces a small reaction piston downwards thereby increasing the tension in the injector spring as a result the injector needle momentarily closes meanwhile because the piston is still moving downwards the chamber pressure continues to rise when it reaches 300 bar it overcomes the increased tension of the injector spring causing the needle to lift for a second time and the main injection cycle commences because fuel is pumped into the chamber at a far greater rate than it can escape through the nozzle the chamber pressure can reach two thousand five hundred bar this high pressure provides excellent atomization the main injection cycle ends when the ecu opens the solenoid valve allowing the highly pressurized fuel to escape back into the supply line by the way the high pressure chamber always receives more fuel than required and this excess fuel is directed back to the tank via the return line the returning fuel also cools the pump injector units and removes any trapped vapour bubbles we hope you can now appreciate that the operating principles of the system are both ingenious and yet fairly straightforward use the play button to see a complete animation of the injection process you can also click on the arrows adjacent to the text to play the animation from that point onwards when you are ready to answer some questions on system fundamentals click on the forward arrow how are the pump injector plungers operated like many of today's fuel systems the pumpered user system relies on an advanced processor controlled engine management system the control unit receives input data from numerous sensors and several auxiliary signals it also constantly exchanges information via the high-speed drive can network with other control units such as those of the abs automatic gearbox and instrument panel in addition the engine control unit via the gateway can communicate with control units connected to the lower speed comfort can including that of the air conditioning system the engine control unit is also responsible for controlling numerous actuators in addition for diagnostic and programming purposes it can communicate directly with the vas 5051 or the vas 5052 many of the systems input sensors such as the air mass meter may be familiar however the way in which their signals are utilized is a little different to previous applications move your mouse over the sensor symbols to see the names of the input sensors within the system when you've finished click on the forward arrow to move on so let's take a look first at those which monitor the movement of the crankshaft and camshaft to activate the appropriate pump injector solenoid valve on starting the engine the system must be able to determine which cylinder is on the compression stroke the information is provided by the hall sensor g40 which is positioned just below the camshaft sprocket it scans the sensor wheel teeth as they rotate with the camshaft each cylinder is identified by a unique tooth arrangement ranging from a single tooth for cylinder four to two teeth separated by a 30 degree gap for cylinder number one by comparing the whole signal against the signal received from the crankshaft position sensor the system can calculate which injector solenoid to activate first if the whole sensor signal fails then the control unit utilizes the engine speed sensor signal instead allowing the engine to continue to run the engine speed sensor g28 is a permanent magnetic inductive device it monitors a sensor wheel that's attached to the crankshaft around the sensor wheel circumference are 59 teeth and two gaps the gaps are offset by 180 degrees and these provide the crankshaft position signal the 59 teeth supply the control unit with engine speed information should the engine speed sensor fail no substitute value is available and therefore the engine will stop note that on later vehicles the inductive type engine speed sensor is replaced by a hall type now let's consider the temperature sensors the system incorporates three temperature sensors one of which is used by the control unit to calculate fuel density the density of the fuel which varies according to temperature needs to be taken into consideration when determining the injection timing and the quantity of fuel injected the sensor is in the fuel return line between the pump and the filter in the unlikely event of the fuel temperature signal failing the control unit calculates a substitute value by using the signal from the engine coolant temperature sensor the signal from the engine coolant temperature sensor g62 is used in controlling the glow plug circuit and to calculate the fuel injection quantity during the warm-up period should it fail then a substitute signal from the fuel temperature sensor is used instead for the control unit to regulate the turbocharger's boost pressure it utilizes two sensors they measure the temperature and the pressure in the intake manifold as you can see both sensors are integrated into one component and a loss of performance will result should either fail there are five sensors left that we haven't talked about yet use your mouse to roll over the symbols and click on the sensors that you haven't yet explored when you finished exploring click on the forward arrow to move on the ecu also receives additional input signals from other areas of the vehicle for example the air conditioning system signals when it's about to switch on the compressor allowing the engine to compensate for the additional load a signal is also received which informs the ecu of the alternator's power output other auxiliary input signals come from the cruise control system and the road speed sensor let's now have a look at the actuators of the pump producer system move your mouse over the actuator symbols to see the names of the components within the system when you've finished click on the forward arrow to move on probably the most important components of the pumped user system are the injector solenoid valves they are used by the control unit to determine fuel volume and injection timing for example if the duration for which the valve is energized is extended more fuel will be injected reducing the energized time results in less fuel being injected similarly by energizing the solenoid either earlier or later the point at which the fuel is injected can be altered closing the solenoid valve earlier will advance the injection timing and vice versa a common characteristic of diesel engines is the shutter that occurs when the engine is turned off it's caused by the high compression pressures in the cylinders to help overcome this the engine incorporates an intake manifold flap which interrupts the air supply as the engine is switched off so helping to eliminate the shutter the vacuum activated air flap is controlled by the changeover valve n239 click on the graphic to see where the valve is located intake manifold boost pressure on the 1.9 and 1.2 liter engines is provided by the now familiar turbocharger with variable turbine geometry its output is regulated by the ecu via the charge pressure control valve click on the graphic to see where the valve is located the valve receives a variable duty cycle pulse from the ecu the width of which determines the quantity of vacuum reaching the turbine vane actuator detailed information regarding variable vein geometry please refer to cell study program 190 as you might expect to help reduce oxides of nitrogen emissions the engine also includes an exhaust gas recirculation system it's regulated by the ecu via an exhaust gas recirculation valve the engine's glow plugs are also controlled by the ecu and their operation depends on input signals from both the engine speed and coolant temperature sensors the system operates as follows when the ignition is turned on the ecu checks the coolant temperature if it's below 90 degrees c the globe plugs and the warning lamp are switched on when the light goes out the engine can be started to help reduce noise exhaust emissions and to improve idling immediately after starting an afterglow phase always takes place irrespective of the coolant temperature afterglow lasts for no more than four minutes and is interrupted once the engine reaches 2500 rpm because of their high efficiency tdi engines generate very little waste heat therefore in cold climates the coolant may take a long time to reach operating temperature to overcome this the engine coolant circuit includes supplementary heating elements depending on the available spare capacity of the alternator the engine management ecu can switch on one two or all three elements as required on the three cylinder engines an electric ptc element is fitted instead it's located next to the normal heat exchanger and directly warms the air entering the interior most modern engine management systems pass on signals to other areas of the car and the pumped user system is no exception it for example supplies engine speed signals to the rev counter and fuel consumption data to the multi-function display it's also responsible for controlling the cooling fan run-on period after the engine is switched off ecu will also override the air conditioning system by switching off its compressor during engine starting rapid acceleration high temperatures or if operating in the emergency running program so that completes our look at the pump injection management system when you're ready to answer some questions on engine management click on the forward arrow the smallest engine is the 1.2 liter three cylinder unit fitted to the lupo three liter and because of its all alloy construction is extremely light nevertheless the engine delivers forty five kilowatts of power at four thousand rpm and a hundred and forty newton meters of torque whilst at the same time returning incredible fuel economy note that although the lupo three liter is not currently available in the uk it is widely available elsewhere in europe in construction apart from it having three cylinders the larger 1.4 liter unit fitted to the polo for example is very different it has a cast iron cylinder block with conventional cylinder head bolts its torque output is impressive 195 newton meters at 2 200 rpm whilst providing a maximum of 55 kilowatts of power at 4 000 revs both three-cylinder engines incorporate a counter rotating balancer shaft it's within the sump and is driven by the same hydraulically tensioned chain that drives the oil pump note that for timing purposes when refitting the chain both colored links should be correctly aligned to their reference marks on the sprockets the 1.9 liter pumped user engine is based on the familiar four-cylinder engine without intermediate shaft and a variety of outputs are available depending upon the model all four-cylinder engines are equipped with a turbo charger and intercooler exhaust gas recirculation and an oxidization catalyst because of the high combustion pressures these engines use trapezoidal pistons and conrods the trapezoidal design allows the high down force acting on the piston crown to be distributed across a wider bearing contact surface the pump injectors are capable of generating an injection pressure of about two thousand bar to rotate the camshaft against such pressures requires a large force and because of this the tooth belt and its drive mechanism have received some design changes for instance the belt is five millimeters wider than in previous models the camshaft sprocket incorporates a vibration damper and to prevent rapid belt wear some of the teeth on the crankshaft sprocket have slightly wider spacing this is because during the injection cycle the high pumping forces stretch the tooth belt and temporarily increase the pitch of its teeth this could cause the belt to be pinched by increasing the space between these particular teeth the momentary change in pitch is compensated for and the belt is no longer pinched incidentally by using a hydraulic tensioner the constantly changing loads within the belt are also automatically compensated for if replacing the belt then always refer to the workshop information but this is basically how it's done first turn the crankshaft until the mark on its sprocket is at the top and the four-cylinder arrow on the belt guard aligns between the two lugs on the camshaft sensor wheel to prevent any movement the camshaft and crankshaft should be locked using the special tools when fitting the crankshaft tool it's important that the reference mark on the sprocket aligns with that on the tool next using the pin wrench hold the tensioning roller whilst releasing its securing nut then turn the roller anti-clockwise until it reaches the stop throughout this part of the course you can follow the action by clicking on the arrows under the image at this point insert the special tool to lock the hydraulic tensioners push rod now turn the roller clockwise to the opposite stop the idler roller can then be removed finally the toothed belt can be removed note that if reusing the belt mark its direction of rotation before removal to refit the belt start by loosening the camshaft sprocket securing bolts and aligning the sprocket into its center position hand tighten the bolts to remove any free play install the toothed belt by placing it in sequence around the camshaft sprocket tensioning roller crankshaft sprocket and water pump the idler roller can then be refitted now turn the tensioning roller anti-clockwise until the locking plate can be removed from the tensioners push rod then re-tension the belt by turning the roller clockwise until there's a four millimeter gap between these two components at this point re-tighten the securing nut to the correct torque the camshaft sprocket bolts are then re-tightened and the mandrel and crankshaft stop can be removed turn the crankshaft twice in the direction of normal rotation and back to the tdc position on cylinder number one now verify the setting by inserting the crankshaft locking tool and the camshaft mandrel finally check the gap at the hydraulic tensioner and if incorrect readjust the tensioning roller after making any corrections always rotate the crankshaft twice and recheck the settings again by the way apart from the different location of the camshaft reference marks the procedure for replacing the belt on the three cylinder engines is basically the same now let's consider the onboard diagnosis features using the vas 5051 when problem solving guided fault finding provides one of the best ways of approaching initial fault diagnosis but in some instances it may be helpful to select the vehicle self-diagnosis mode and choose the read data block function to access both static and dynamic data about individual components the features are quite advanced and include a means of testing injectors it's carried out by measuring the current draw of the injector solenoid valves at the point where the valve closes a distinct knee appears in the current draw curve the knee is used by the ecu as an indication of the beginning of the injection period referred to as bip if the self-diagnosis system detects that the bip is out of tolerance the ecu will record a fault code in its memory on this vehicle a fault has been detected with the solenoid or circuit of number three injector unit the next step is to confirm the fault by using the function zero eight read data block entering the display group zero one eight allows fast verification of faulty injector solenoids and should always be referred to when an injector solenoid fault code is recorded enter the code by using your mouse to click on the buttons and then click on q to confirm display group 18 shows a status value for each cylinder the specification of which should read zero if anything other than a zero is displayed it's an indication of air in the fuel delivery system or that there's a problem with the applicable injector solenoid or its associated wiring a full explanation of the correct diagnostic procedure can be found in the repair information however it's always a good idea to start by eliminating the possibility of faults within the fuel system during the process you will need to test the supply line pressure it's done by connecting the appropriate pressure gauge to the service connection point on the pump and then starting the engine compare the pressure with the specification in the manual contaminated or poor quality fuels can cause erratic running idling and stalling problems particularly when hot supplying the engine from a temporary alternative fuel supply will quickly verify if poor fuel is the actual source of the problem testing the injector solenoid and its wiring is done by checking its resistance value and the wiring for continuity alternatively you can compare the injector solenoids oscilloscope waveform with that of one from a known good cylinder if you suspect a faulty injector then always confirm your diagnosis by exchanging it with one from an adjacent cylinder if the fault moves to that cylinder it will confirm your diagnosis providing you follow the procedure in the workshop information replacing an injector unit is reasonably straightforward start by removing the belt guard and cam cover turn the engine until the camshaft lobes on the cylinder of the defective injector are pointing upwards then slacken the locking nut and unscrew the adjusting screw until the bottom edge of the rocker arm contacts the injector unit spring next remove the rocker shaft securing bolts starting from the outside and working inwards and lift off the shaft the injector units tensioning block can be removed next after removing the wiring plug carefully position the special slide hammer and then withdraw the injector unit from the cylinder head note that new injector units are supplied complete with new oil and heat shield seals if for any reason the old unit is being refitted always follow the instructions in the workshop information and replace all seals check that the seals are not twisted and then carefully push the injector unit fully into the cylinder head next fit the tensioning block into the slot on the side of the injector unit note that if the injector unit is not fitted at 90 degrees to the tensioning block then serious damage to the cylinder head will occur therefore using a vernier gauge check the distance between the injector and the outer edge of the cylinder head the correct dimensions for each cylinder are specified in the workshop manual once aligned follow the instructions in the repair information tighten the securing bolt and refit the rocker shaft now the injector unit must be correctly adjusted to prevent the pump piston from contacting the bottom of the high pressure chamber align a dial gauge on top of the injectors adjusting screw and then rotate the engine until the rocker arm is fully down and remove the gauge now turn the adjustment screw clockwise thereby depressing the spring until a firm resistance is felt at this point unscrew the screw for 225 degrees of rotation and then tighten the lock nut in addition to reading confirming and erasing bip fault codes the 5051 offers all the familiar diagnostic functions including final control diagnosis it activates a number of actuators and is particularly useful for testing the operation of the egr valve charge pressure control valve intake manifold flap changeover valve and so on as we demonstrated earlier a particularly useful feature for fault diagnosis is the zero eight read data block function which allows around eighteen display groups to be selected in addition to group eighteen already mentioned display group zero zero zero contains data unique to the pumped user system therefore may be new to you try it for yourself choose the read data block function by clicking on it now enter the code zero zero zero by using your mouse to click on the number display group zero zero zero is useful for providing a quick system health check it displays ten values indicating engine speed commencement of injection accelerator position quantity of fuel injected intake manifold pressure atmospheric pressure coolant temperature intake manifold temperature fuel temperature and air mass value the correct specifications for these values both at idle speed and under load at three thousand rpm are in the workshop information instructions on what to do if any of the values are outside the specifications are also supplied if the need ever arises to replace the engine control unit then remember these important points firstly using function 0 7 code the replacement to match the engine and country then use the adaptation function to match the control unit to the vehicle's immobilizer system finally remember that in this module we've highlighted only the most significant features of the pumped user self diagnosis system and in most instances starting with guided fault finding is your best approach to fault diagnosis for information regarding repairs and specifications then refer to the relevant section within the workshop information you

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Keywords: vag, volkswagen, audi, vw, engine, motor, timing chain, repair, tdi, diesel, pump, how to, adjustment, timing belt

Id: Tzl0R7_K388

Length: 50min 56sec (3056 seconds)

Published: Tue Sep 15 2020