How to align the ignition on a diesel engine
One of the main differences between a diesel engine and a gasoline engine is the principle of ignition of diesel fuel. Ignition of the fuel-air mixture in the diesel engine is realized by self-ignition of diesel fuel from contact with air pre-compressed and heated in the cylinders as a result of such compression.
In the diesel engine, ignition timing involves changing the advance angle of fuel injection, which is injected at a precise moment at the end of the compression stroke. If the angle is not within the optimum range, then the fuel injection will not be timely. The result will be incomplete combustion of the mixture in the cylinders, which causes destructive imbalance in the engine.
So, by ignition system of a diesel engine we mean the most important element of the power unit feeding system. high pressure fuel pump (HPF). In most of diesel engines, this very device in combination with diesel injectors is responsible for the timely metered flow of diesel fuel into the engine cylinders.
Engine ignition adjustment can be performed only if the engine and the HPF are in good working order, so the master always performs a check at the beginning of the work. Centrifugal advance angle regulator is used on vehicles with mechanical HPF, and its defects can produce symptoms, completely similar to the late injection timing: when rpm is reached, the angle does not change, injection becomes late.
If necessary, adjustment of clearance between the pump plunger ends and discharge valve seats, in the centrifugal mechanism must be performed. These works are charged separately as repair of high-pressure fuel pump.
Setting the marks can not always give the correct injection angle, especially on an old and worn out fuel injection system. In this case, the fuel start angle (required accuracy. up to 1 degree) is set by the real position of the crankshaft and the beginning of the fuel supply to the nozzle of one of the cylinders.
How to set the injection timing on a diesel
Greetings to all readers of my blog.Decided to share my experience on setting the injection timing on AAZ and AEY (M-TDI) diesel engines.So, let’s assume you have a diesel engine with a mechanical fuel injection valve (VAG family), which has no timing belt and with worn installation marks.Approximately so :-).
Naturally you start to digest a lot of information from those.books and forums. And learned that you need special tools for this, namely: a plank to fix the camshaft, a roller to fix the pulley and micrometer dial type clock to set the injection torque. And these devices are really needed. But there is one “but”, we do not have them at the moment and the engine needs to be started.And so, how do we set the timing belt and injection torque, if there are no devices?At the beginning we need to align the timing gear. Let’s start with the camshaft.Razdorovanivayu camshaft so that the cams of the first cylinder looked up, and the slot on the back side of the face of a camshaft should stand parallel to the body of the gasket.
Then set piston of the first cylinder to TDC, and for this align the mark (0) on the crankshaft flywheel with the mark in the window of the gearbox. If there is no gearbox, the distance between the bolt holes (above) we divide by half, put a mark on the block, it will be TDC. Align (0) with this mark.
Next is the fuel injection unit.To install the plunger at the time of first nozzle injection, we need to align the smallest hole in the plunger pinion with the hole in the plunger bracket.
Exactly align them is not possible because of the valve spring in the housing of the fuel pump. So the pulley will go counterclockwise by one tooth. But that’s okay.Moving on.install the timing belt on the crankshaft pinion, bring it to the fuel injector pinion, turn clockwise the crankshaft pinion one tooth clockwise (watch the holes coincide), put the belt on the fuel injector pinion. Then carefully remove spanner, pinion gear of fuel injection system moves by one tooth counterclockwise under the influence of a spring, and the mark (0) of the crankshaft also moves by one tooth.Then we bring the timing belt to the camshaft pinion, but before putting on the belt we need to turn the camshaft pinion one tooth counterclockwise, and then we put on the belt and tighten it with the tension pulley.
Put the mark (0) back in its place and see that all the marks are in place :-).
Next, align the injection torque of the fuel pump, to do this, align the marks on the fuel pump and its gear.
Align the marks as follows, all marks of the timing belt should remain on their places. The marks are aligned by moving the fuel injection housing, and the pinion stays in its place. After that the tvd tightens up. You are ready :-), you can start the engine :-).When repeatedly checked with an hour gauge, the injection torque is within 0.84-0,92.
That’s basically it :-).Thanks for the tip :-). Good luck to all :-).
It happens that after changing the timing belt (timing belt) or fuel pump (fuel pump) on a diesel, it is difficult to find the marks on which to align the fuel pump pulley to ensure the timely delivery of fuel. How to be?
one can, of course, try to “catch” the necessary position of the fuel pump pulley by the “scientific method”, t.е. put it in one position and try to start the engine.
If the engine fails to start, turn the oil pump pulley 3-5 teeth to either side relative to the timing belt and try again.
Started, but the early injection is knocking hard, it means you need to turn the pulley 1-2 teeth against the direction of rotation and start the engine again.
Started, but the smoke and runs very soft late injection, you need to turn the pump pulley 1 tooth in the direction of its rotation.
After it is no longer possible to achieve a precise adjustment by changing the belt, it is necessary to loosen the nuts fixing the fuel injection pump and turn it around its own axis to achieve the desired position (this is the position when the warm diesel runs on the brink of detonation; detonation knocking in the engine is very loud and cannot be ignored).
The method described above is inconvenient and harmful to the engine.
Therefore it is better to do the following: unscrew a high pressure tube from the first cylinder nozzle and put a transparent tube on it (the tube) or non-transparent, but then you put a glass tube into it (the length of non-transparent piece should be as less as possible). The tube should look up so you can see the fuel filling it up.
Then turn on the ignition and twist the pump pulley with a wrench (timing belt removed from the pump) until fuel comes in the tube (we need its level in the tube).
Then slowly, with small motions rotate the crankshaft pulley and look carefully for the fuel level in the tube, as soon as the level is rustled, it means that the fuel starts to flow to the injector of the first cylinder, and, having stopped further rotation of the pulley, put a mark on it.
Next, align the crankshaft, camshaft and now the HPF at the very same mark that we have determined.
Exactly set the injection torque is necessary to turn the pump, if it was removed, and if you only took off the belt, and before the injection torque was set, you should not touch the HPF.
To avoid looking for marks and catching the moment of injection after an engine repair, before removing the timing belt, set the crankshaft on the mark and paint your marks or trace the factory ones. It’s much more reliable and saves time.
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One of the main differences between the diesel engine and gasoline engine is the principle of ignition of diesel fuel. Ignition of the fuel-air mixture in the diesel engine is realized by self-ignition of diesel fuel from contact with air pre-compressed and heated as a result of such compression in the cylinders.
The ignition timing on the diesel engine involves changing the angle of advance of fuel injection, which is fed at a clearly defined moment at the end of the compression stroke. If the angle is set differently from the optimum parameters, then the fuel injection will be untimely. the result is incomplete combustion of the mixture in the cylinders, which causes devastating imbalances in the engine operation.
So, the ignition system of the diesel engine is the most important element of the power unit power supply system. high pressure fuel pump (HPF). In most of the diesel engines this device in a complex with diesel injectors is responsible for the timely dosed feed of diesel fuel into the engine cylinders.
Replacing the fuel pump
It is not so difficult to replace it, therefore we buy a new one, preferably the checked up firm, stock up a standard set of keys and go, install a new pump. First of all disconnect the battery terminals, in order to avoid a short circuit. Working with fuel is a fire hazard, so the slightest spark can have disastrous consequences. Now remove the rear passenger seat cushion on the right side. Under it is a small rubber mat. remove it. After that, it is necessary to remove the plug from the gas tank hatch. On some models it is fixed with bolts, on some others with special pawls. We remove it to the side and get access to the immersion module of the gas tank of Renault Megane. Now it is necessary to disconnect terminals, which are connected to fuel pump power module and fuel level indicator of engine 1.5. This is done with an ordinary flathead screwdriver
Very carefully remove the block, trying not to damage its plastic part. Then, having unscrewed the clamps with a shaped screwdriver, take aside the fuel pipes
There are two of them. Be ready, that there will be a leak of fuel. This is quite normal, because the fuel system holds pressure for a while. By the way, tubes, depending on the year of automobile release, can be both on clamps and collars. Then the most difficult stage is to be performed. to unscrew the cap nut of the submersible module. Here you have to use your imagination. One does it manually, with the help of big heads, and someone makes special strippers from thin metal It is important not to damage the plastic part of the union nut, otherwise you will have to buy the whole module. Sleeve nut is easy enough to unscrew and you can use WD-40 or other type of grease if you need.
On the removed fuel module, do not forget to put the marks on the fuel level gauge to assemble everything in reverse order. It is also worth noting the location of contact terminals. Because most drivers when performing this procedure, at the end of the work there are problems with electrical connection. The easiest way is to take a picture of their location and then, according to the photo, assemble everything in the reverse order. After disconnecting all wiring and releasing the latches, the fuel level indicator is removed, and now the way to the fuel injection pump is open. Dismantle the old pump. Be very careful. the module is made of plastic and therefore very fragile
One careless movement can break important parts. It is better to do the job slowly so you don’t have to spend a lot of money
Now install the new fuel injection pump on the engine 1.5 and reassemble everything in the reverse order.
In principle, at this work on the replacement of the fuel pump on the car Renault Megane with the engine 1.5 has come to an end. Recall that if you do everything in the sequence described above, there will be no problems when replacing
It is important to mark all removable parts of the same type. terminals, nuts, or remember how they were installed at the factory. By the way, when disassembling the submersible module, do not forget to clean the contact terminals, which are located inside it
In most cases, they oxidize quite quickly in contact with petrol vapors, and the electrical contact is broken as a result. In the course of operation, if you neglect this advice, you may encounter traction problems, because the electronic control unit will not signal to the fuel injection valve properly.
Injection torque control
The following system overview shows the sensors which are used to determine the start of injection. The signal from the engine control unit is converted by the fuel pump control unit into a signal for the advance injection control valve. The purpose of the injection torque control is to adapt the injection torque to the engine speed.
Principle of operation: When the rpm increases, injection must proceed earlier. The fuel is accelerated by the injection regulator. The control piston is pressed against the piston of the injection regulator by the force of the spring. The ring cavity of the control piston is filled with fuel under pressure through the hole in the internal space of the fuel injection pump. The valve controls the advance fuel pressure in the annulus of the pilot piston.
When the rpm increases, the injection advance control valve increases the fuel pressure in the annulus. This causes the control piston to push away from the injection regulator piston, overcoming the force of the spring, and opens the channel. Fuel flows into the cavity behind the regulator piston.
Fuel pressure causes the piston of the injection regulator to move to the right. The piston in the injection regulator is connected to the cam follower so that the horizontal movement of the injection regulator turns the cam follower in the direction of advance of the injection.
The function of the HPV is to make the fuel flow at exactly the right moment and at exactly the right pressure to the engine components. The quantities of fuel have to be precisely metered. The block is responsible for a good fuel circuitry throughout the system.
Several types of pumps are used today. There are so-called “accumulator” models and direct injection pumps. The second version is considered more modern and advanced, the necessary atomization is provided by the movement of the plunger.
The PP or plunger pair is the heart of the pump. It is an oblong, small-sized element that fits the cylinder as closely as possible. PP is several times smaller in diameter than the length. One of the clever design features that increase the importance of the PP is the clearance between the piston and the cylinder. It never exceeds 1-3 microns.
The cylinder consists of one or two inlet ports through which fuel is fed. It is discharged through a valve that pushes the fuel out.
- Distributive type of pump, in which the pistons are installed so as to perform injection and dispersion into the existing cylinders.
- An in-line pump that has only one PP.
- Trunk HPF, whose tasks include pumping gasoline or diesel fuel into the fuel rail or accumulator (storage).
HPF adjustment on the engine
The HPF is synchronized with the engine by means of the setting marks for the start of injection (closing of the channel). These marks are on the engine and on the HPF.
Usually the engine compression stroke is used as the basis (reference point for injection torque adjustments, although other options may be used for a specific engine model). In this regard, it is important that the manufacturer’s instructions be followed. In most cases the reference marks for closing the channel are located on the engine flywheel, V-belt pulley or dampers. There are several possibilities for adjusting the HPF and setting the correct injection start (closing of the channel).
- The fuel injection pump is shipped from the factory with its camshaft locked in position. after the HPF is mounted on the engine and bolted down with the crankshaft in the proper position, the HPF camshaft is released. This well proven method is inexpensive and is becoming more and more popular.
- The HPF is equipped with a closing indicator on the end of the regulator that must be aligned with the setting marks when the HPF is installed on the engine.
- On the device (clutch) of the injection timing advance there is a mark of closing the hole, which must be aligned with the mark on the fuel injection pump body. This method is not as accurate as the two previously described.
- After the HPF is installed on the engine, the high-pressure overflow method is used on one of the pump outlets to determine the point (torque) of channel closure (t.е. when the plunger overlaps the fuel outlet channel). This “wet” method is also actively replaced by method 1 and 2 described earlier.
Air bubbles in the fuel may impair or even make it impossible to operate the HPF. The units that are installed for the first time or temporarily shut down should be vented.
If the fuel priming pump is equipped with a hand pump, it is used to fill the line, the fuel filter and the fuel injection pump with fuel. The screws for venting (1) on the filter cover and on the fuel pump must remain open until the exiting fuel is bubble free. Air should be removed whenever the fuel filter is changed or work is performed on the system.
Under real operating conditions, air is automatically evacuated from the injection system through a by-pass valve (2) on the fuel filter (permanent venting). Restrictor can be used instead of valve if pump does not have a by-pass valve.
HPF and regulator are best connected to the engine oil system, as.к. with this form of lubrication the fuel injection pump remains maintenance free. Filtered engine oil is fed to the fuel injection pump and regulator through the pressure line and inlet port on the roller tappet or through a special oil supply valve. In the case of an HPF with a base or frame, the lubricating oil is returned to the engine through a return line (b).
Setting injection pump BOSCH VE VAG, VOLVO etc
In the case of a flanged mounting, lubricating oil return may be via the camshaft bearing (a) or via special channels. Before turning on HPF and regulator for the first time, they must be filled with the same oil as the engine. In the case of an HPF without a direct connection to the engine oil system, oil is injected through the cap after removing the cap to remove air or filter. The oil level in the pump is checked by removing the oil level screw on the regulator at the intervals prescribed by the engine manufacturer for changing the oil in it. Excess oil (increased amount due to oil leakage from the lubrication system) must be drained, and if there is not enough oil, fresh oil must be added. When the HPF is removed or when the engine undergoes major repairs, the lubricating oil must be changed. Split-type fuel injection units and regulators with separate oil supply have their own dipstick to check oil level.
Split fuel injection pump (VE pump). AKA the end pump
The range of application of this type of pumps is wide. passenger cars, trucks, commercial vehicles, tractors, agricultural machinery, etc. Engines with this type of pump are available in 2, 3, 4 and 6 cylinder sizes with a maximum power per power cylinder of 20 kW.
The main manufacturers of this type of pumps are: Bosch (Bosch), Zexel (Zexel) and Denso (Denso), but there are also little-known Diesel Kiki (Zexel) and Korean Doowon. which once bought the license from ZEXEL to produce these pumps.
The type VE split fuel injection pump is divided into two modifications:
First I suggest to pay attention to the principle of operation of the distributive type fuel injection pump (VE) on the example of Denso pump
- Fuel is pumped from the tank to the fuel filter by the fuel priming pump (DNFT), the filter removes water and dirt from the fuel.
- Fuel is then pumped into the high-pressure pump housing by the fuel injector.
- Fuel which is in the fuel injection pump housing is pushed by the plunger through the pressure valves to the nozzles and is injected into the combustion chamber.
- Part of the fuel which reaches the injectors is used for lubrication and then returned to the fuel tank.
- Part of the fuel that enters the high-pressure pump housing is used for pump lubrication and parts cooling, then it returns to the fuel tank through the drain bolt hole
Construction of VE Bosch, Zexel
Let’s consider the most important units of a single-plunger high pressure fuel pump of distribution type (ВЕ). I suggest you consider the nodes, according to the principle of the pump, from the booster pump to the discharge valve.
As the pump rotates, 4 plates (as seen in the photo) pump the fuel under pressure through the filter into the pump housing, by means of a control valve, the pressure varies with the speed of the engine.
During operation the plunger combines rotation with reciprocating movement, thereby it distributes high-pressure diesel fuel supply to all injectors in turn.
Plunger design of the VE distributor fuel pump:
When the internal combustion engine rotates, the drive shaft of the fuel injection pump rotates the cam washer together with the plunger through a coupling with the same speed. Fuel pump shaft rotates at half the speed of the engine.
- the pump rollers are located on the roller ring 2;
- cam washer 3 is permanently held by the plunger spring pressed against the pressure rollers;
- when rotating the cam washer (wave washer) 3, the cams run over the rollers 2, forcing the plunger 4 to perform reciprocating motion;
- in the cam washer 3, the number of knobs on it (cams) is a multiple of the number of engine cylinders;
- pump plunger 4 distributes fuel sequentially to injectors per one turn (the example shows a 4-cylinder engine);
- reciprocating motion of the pump plunger is used for fuel intake (groove 6) and its delivery to injectors under high pressure, through the groove 8;
- The amount of injection and delivery (cyclic) is adjusted by changing the position of the adjusting sleeve 5, under the control of the mechanical regulator.
For clarity of the plunger operation please see the video of the pump elements involved.
They are located in the supply channels and are made in such a way that they suck unused fuel back into the pump housing to keep the supply channels full of fuel. The number of these valves depends on the number of engine cylinders.
How the VE fuel injection valve works
- When the fuel pressure increases it opens the discharge valves and keeps them open;
- When fuel injection ends, the valves are pushed back by the spring;
- When the valves return to the lower position, the supply lines are closed and the fuel is sucked back in;
- The pressure in the lines going to the injectors drops quickly, about 20 kg/cm2, to prevent fuel leaking from the injectors;
- At the same time, the discharge valve fits tightly against the seat, shutting off the high pressure line from the pump.
In this article we have reviewed the most important working elements of the VE distributor HPV. There are many other important mechanisms in this type of pump, which we will describe in more detail in the following reviews.
To illustrate the number of elements involved inside this type of pump, I will attach a clipping from the catalog using the pump 104746-1342, aka 9460612334 as an example
The Bosch VE pumps (boxed designation R or L indicates the direction of rotation of the fuel injection pump) are listed briefly:
Schematic diagram of fuel supply system of diesel engine with single plunger injection pump
The schematic diagram of the diesel fuel supply system with single plunger distributive fuel pump (SCP) with end cam drive of the plunger is shown in the figure:
Fuel from the tank 11 is pumped through the fuel line of low pressure to the fuel filter 10, then it is sucked by the fuel pump of low pressure and then directs to the internal cavity of the fuel injection pump housing 4, where the pressure is created approximately 0,2 0,7 MPa. Fuel then enters the high-pressure pumping section and with the help of a plunger. distributor in accordance with the order of the cylinders is fed through the high pressure fuel lines 6 in the nozzle 8, resulting in fuel injection into the combustion chamber of the diesel. Excessive fuel from the fuel injection pump housing, nozzle and fuel filter (in some designs) is drained through fuel lines 7 back to the fuel tank. Cooling and lubrication of fuel injection pump is provided by the fuel circulating in the system. Fine fuel filter is important for normal and trouble-free operation of HPF and nozzle. Since plunger, sleeve, delivery valve and injector elements are precision parts, a fuel filter must trap the smallest abrasive particles of 35 microns. An important function of the filter is also to trap and precipitate the water contained in the fuel Moisture in the internal space of the pump can lead to failure of the pump due to corrosion.
A fuel pump gives to the diesel engine cylinders a strictly dosed amount of fuel under high pressure at a certain moment depending on the load and speed mode, so the characteristics of the engines significantly depend on the work of the fuel pump.