Bosch VE-EDC VP15, VP34, VP36, VP37
These pumps are one of the first developments of Bosch in a line of distribution injectors.
This article is not the final truth. Rather, I’m sharing my experience in inspecting cars with this fuel injection pump. Been running into these pumps for the last 15 years. Still cause difficulties in diagnosis (finding defects). Well, let’s try to deal with these “beasties” and methods of their “taming.
Let’s start with the device and the logic of their work. It may sound boring to some people, but that’s how I start training automobile diagnosticians. “Understand the logic of work and do everything well”!”. You won’t have enough manuals for the rest of your life and you can’t foresee all the defects.
Omitting the basics of injection theory, I will note the basic requirements for diesel injection systems:
Ways to control the cyclic feed.
These pumps have a way of controlling the cyclic rate by moving the control lip (colloquially referred to as the sleeve).
- Plunger on suction stroke: Plunger moves to the left, fuel inlet open. Fuel line to the injectors is closed.
- End of suction, start of discharge. 2 Plunger turns to shut off the fuel intake. At the same time the fuel supply line to the injectors opens. Plunger in home position.
- Start of feed: Plunger moves to the right. Fuel supply line is closed. Fuel line to the injectors is open. Once a defined pressure is reached in the pressure line, the injector opens. injection begins.
- Pressure in the ram space rises gently from “0” to the maximum value. is not a constant value. That’s why at maximum plunger pressure for these pumps of up to 1,000 bar. Average effective pressure barely reaches 500 bar.
- The start of injection is determined by:2a. Plunger start. Initial exposure of the HPF, position of the wave washer. 2б. Nozzle opening pressure. 2с. Compression wave travel time from plunger to injector (injection delay time). Determined by the length and construction of the pressure line.
HPF rotor position. Ignores the injection delay. The position is determined by the needle sensor. 4.
The regulating lip (sleeve) relieves the pressure in the sub-plunger chamber to the pump cavity. Injector pressure drops, injector closes. The end of injection takes place. The position of the regulating sleeve (lip) is set by the control unit.
- Injection starts with: Position of the roller ring against the shaft (cam washer), Initial position of the fuel injection pump, Fuel injection pump pressure, Injector opening pressure.
- The end of injection is set by the position of the control lip (sleeve).
- Injection Angle (PI) is only set by the control unit using the position of the cam disc. The pre-exposure of the fuel injection pump is not taken into account. Also the injection delay time (if there is no needle stroke sensor) and nozzle opening pressure are not taken into account.
- The cyclic delivery is regulated only by the time of pressure release into the cavity of the fuel injection pump by moving the regulating edge (sleeve). The start of injection is not controlled by the unit. Only the end of delivery is monitoredNote: The Bosch, Denso, Delphi and other pumps are the same in principle. Differences. only in constructional designs.
Regulating sleeve is moved by the actuator With no voltage on the winding under the action of a spring (not shown in the figure), the rotor is in the initial position. The sleeve is in zero flow. When voltage is applied to the winding, the rotor turns and the lever shaft (actuator) moves the adjusting sleeve in the direction of the maximum feed. But we do not only need the zero and maximum feeds! How to put the rotor in an intermediate position? The actuator is controlled by pulse width modulation (PWM).
The winding voltage is as follows:
As can be seen, the pulse repetition period T does not change. But the width of pulse Т has different value. Under the influence of this voltage the rotor starts to rotate in the direction of maximum rotation. But then the pulse is gone. the rotor comes back to zero rotation. The pulse repetition frequency is large enough (up to 10 kHz) the rotor does not have enough time to move from one end position to the other. T takes some position, determined by the width of pulses in relation to the period of pulse repetition (pulse duty cycle). By connecting an oscilloscope to the winding input, we can see just such pulses. Depending on the desired cycle rate, the pulse width changes while the pulse repetition period does not change. According to the readings of various sensors, the control unit calculates the pulse duty cycle per winding. But windings can be different, and so can the stiffness of the return spring. Plus all sorts of disturbing factors. The rotor can take a completely uncalculated position. And its position directly determines the accuracy of cyclic feed. What to do??
The position can only be saved by the rotor position sensor (regulating sleeve). The control system becomes a closed loop system with feedback:
The control unit varies the pulse repetition until the rotor is in the calculated position according to the sensor. Originally a standard potentiometric sensor was used as a rotor position sensor. But they do have one disadvantage. wear and tear on the track. Started to give wrong readings of the real position of the adjusting sleeve. With all the very unfortunate consequences that this entails. So later on a half differential switch with a closing ring was used.
The ECU sends a reference signal to the magnetizing coil (reference coil). Frequency on the order of 10 kHz. Short-circuited copper rings shield the generated magnetic field. Changing their positions, we make initial calibration of the sensor (adjustment of the initial point and steepness of the characteristic). An alternating magnetic field induces an alternating voltage signal in the measuring coil. The field in it is shielded by the measuring ring connected to the regulator shaft. The voltage induced in the measuring coil therefore depends on the position of the rotor (position of the controlling sleeve). Since both coils are identical, there is temperature compensation and other disturbing factors are eliminated. The use of this circuit has made it possible to determine the position of the regulating sleeve more accurately than in the resistive circuit. And it’s more reliable because there are no rubbing parts.
Well, we’ve improved the regulation accuracy. Then we remember that the cyclic feed rate depends directly on the fuel density. Hotter fuel has a lower density. the cyclic feed rate decreases. Colder has higher density. all other things being equal, the cyclic output increases. To adjust this parameter we put the fuel temperature sensor.
The schematic of the HPF cover takes on the following appearance:
- Magnetizing coil (supporting coil)
- Measuring coil
- Actuator winding
- Fuel temp sensor
We understood the logic of the cyclic feed regulation. Time for testing.
Cyclic feed check.
Before us is the Volkswagen Caravelle (Transporter). 2004 year, distributor type fuel injection system with regulating sleeve. Production. Bosch. Customer complaints. does not start. Put it in the parking lot in the evening. did not start in the morning. By the nature of cranking by starter motor defect version is rejected so far. We unscrew the tube to the nozzle. Let’s turn the starter. No fuel coming in.
In diesels with electronic control system, the lack of cyclic feed can be caused:
This is where you start to check. What is bad. Electronics or mechanics? Connect oscilloscope to actuator input. On this model the HPF connector is in a very hard to reach place, so connect it to the ECU output. We lose information about the integrity of the wiring. nothing, we will check it later. Should see the pulses shown above.
Note: It is not always easy to watch the change in duty cycle (pulse width) with an oscilloscope. We get our hands on an ordinary tester. It’s an inertial device. it shows the average voltage of the winding. And that’s what we need!
So, switch on the ignition. The fuel injection pump is in zero feed. the tester shows “0”. Ratio is “0”. Then it goes into idle Tester shows little voltage. The scanner in the data flow at this time shows the degree of displacement of the sleeve about 10%. In four seconds. EDC resets HPF back to zero feed. Tester shows 0 v. scanner. 0%. Push in the starter HPF should go to maximum output. Tester: Approximately 12 volts. Scanner: About 100% (engine cold) Conclusion: Electronic controls (EDC) are good. Problems with HPF.
Checking p.2. Before, we always took off the top cover and visually looked at the rotor position. On this model, it takes a long time to remove it.
I’m lazy. don’t want to do unnecessary work! Connecting an oscilloscope to the reference coil. We see a sinusoidal signal with a frequency of about 10 kHz and an amplitude of about 3 volts (in other models these parameters may be different). Connect oscilloscope to measuring coil of rotor position sensor.
Digital oscilloscopes don’t always work properly at this frequency. I use a cathode ray oscilloscope. We see a sinusoidal signal of small amplitude. Put 12 volts on the winding. You hear a distinct click (it is the washer moved to maximum fuel rate). Signal on measuring coil suddenly increases.
Conclusion: Cap is good. Rotor turns, sensor is intact. Well, then “You have to change the plunger!”. Let’s not jump to conclusions. Remember. plunger does not work without inflation pressure! Check. Connect the pressure gauge to the return. this is the easiest way on these pump models. Pressure at starter is about 1 bar. We see “0”. Cranking pump failure (located inside fuel injection pump)? Change of fuel injection pump? Let’s take our time with the leads. Is there even any fuel in there?? Connect the transparent tube to the flow and return. We see no fuel movement in the supply, but we get clean air at the outlet. Fuel injection pump is blown! Unlike Japanese cars, German cars do not usually have a manual pump. How to Pump an Empty HPF? Manuals are silent.
“Grandpa’s” way: unscrew the return, put a little air pressure from the pneumatic line into the tank. Wait till fuel comes out of return flow. Risk: Too much pressure could damage the tank. If we don’t pressurize it, it won’t work.
Take a plastic bottle from Coca-Cola. We fill it up with fuel. We put a tube in a plug and connect it to flow. Hanging under the hood. fuel flows by gravity. squeezing the bottle with your hands, helping the pumping. And here’s a miracle! Fuel is leaking from return flow line. We press the starter. the car starts with a half a turn.
The car is started. now we have to find the reason of air shortage. I’ll skip the details of the search, I’ll just say. The reason was in the construction of the backspout line from the nozzles. In principle at injectors there is either one or two return pipes.
The first scheme is more preferable for Japanese automobiles. The second. German. The reason is more than trivial. The plug came off. The car was parked overnight on a hill (at a slope). the fuel flowed out through the back drain (was below the level of the fuel pump). Placing the plug, closing the hood. Found the defect and its cause.
Notes: This article uses drawings from official Bosch sources, posted for free circulation.
Features of design
The designers of AFN engine incorporated original design solutions:
- In-line arrangement of the 4 cylinders is the only scheme with perfect balance, when the forces of inertia are fully balanced;
- Cast iron block and aluminum cylinder head to reduce the weight of the powertrain;
- SOHC 8V timing mechanism;
- Belt drive transmission of timing gear and attachments;
- Ignition system from a single coil with a trammel;
- Supercharging with a turbine;
- hydro-compensators in the timing mechanism.
AFN cylinder head assembly
AFN intake manifold
Hydraulic tappets depend on oil quality. Some attachments require periodic maintenance. For example, the pump is changed along with the timing belt, and the intake manifold is periodically cleaned of deposits from the inside.
Combustion chambers of hinged configuration, inclined location of spark plugs on the side of the center of CS: GO. The engine design does not have any complicated solutions except for hydraulic tappets. Cylinders are bored out inside the cast iron block without liners and the surface is honed. This improves maintainability and allows further boring for increased engine output.
AFN cylinder block
The exhaust gas recirculation valve (EGR) is most often silenced by the user. On the one hand increases power, simplifies design, reduces intake valve deposits. On the other hand, the ecological standard of Euro 0 is lowered.
Регулировка цикловой подачи. Audi A6C5 2.5 TDI V6
In the Bosch VP44 diesel mechanical injection system the diesel injectors are opened by the pressure produced by the fuel injection pump. The injection timing and amount of fuel injected is also set by the HPF, which in turn is controlled by the electronic control unit. Injection pressures up to 1000 bar. Such pumps are used on Opel, Audi, Ford, Nissan, BMW, Rover diesel models.
Direct injection system for diesel engine with VP-44 injection pump:
1 fuel tank; 2 fine fuel filter; 3 HPF; 4 HPF ECU; 5 fuel feed control solenoid valve; 6 injection angle solenoid valve; 7 injection advance control valve; 8 engine ECU; 9 nozzle with needle lift sensor; 10 glow plug preheater with a closed heating element; 11 glow plug ECU; 12 coolant temperature sensor; 13 crank shaft speed sensor; 14 inlet air temperature sensor; 15 mass air flowmeter; 16 surge pressure sensor; 17 turbocharger; 18 exhaust gas recirculation valve actuator; 19 surge pressure control valve actuator; 20 vacuum pump; 21 accumulator battery; 22 instrument panel with fuel flow meter, tachometer, and tachometer; 21 glow plug; 23 carburetor; 24 glow plug accelerator; 24 glow plug accelerator; 25 glow plug accelerator; 26 glow plug accelerator; 21 remote control panel with tachometer; 21 accumulator battery; 22 instrument panel with tachometer; 21 fuel gauges with gauges and.д.accelerator pedal position sensor; 24 limit switch (on clutch pedal); 25 brake light contacts; 26 brake light sensor; 27 cruise control unit; 28 air conditioner compressor; 29 diagnostic display with terminals for diagnostic tester
The radial piston injection pump is an electronically regulated injection pump with its own control unit. The pump generates an injection pressure of 1000 bar. The high pressure of diesel fuel makes it possible to achieve a fine atomization of the fuel. This leads to a more complete combustion of the air-fuel mixture and a lower pollutant content in the exhaust gases.
a for four or six cylinders; b for six cylinders¬c for four cylinders; 1 cam washer; 2 roller; 3 guide grooves on drive shaft; 4 roller shoe; 5 pressurizing plunger; 6 camshaft-distributor; 7 high-pressure chamber. The number of cams on the washer corresponds to the number of engine cylinders. In the camshaft housing, the plungers are arranged radially, which gave the name to this type of fuel injection pump. On an upward cam track the plungers together press the fuel into the central high-pressure chamber 7. There are variants with two, three or four high-pressure plungers, depending on the number of cylinders and application conditions.
Distributor body: a filling phase b discharging phase: 1 plunger; 2 shaft-distributor; 3 distributor sleeve; 4 locking needle of high pressure solenoid valve; 5 return fuel drainage channel; 6 flange; 7 high pressure solenoid valve; 8 high pressure chamber channel; 9 fuel inlet end channel; 10 accumulating diaphragm, dividing swap and drain cavities; 11 cavity behind diaphragm; 12 low pressure chamber; 13 distributor groove; 14 discharge channel; 15 discharge valve; 16 high pressure line fitting
In the filling phase (a) on the downward profile of the cams radially moving plungers 1 move outward, to the surface of the cam washer. In so doing the locking needle 4 is in free position opening the fuel inlet channel. Through the low pressure chamber 12, annular channel 9 and needle channel the fuel is directed from the fuel priming pump through the channel 8 of the shaft distributor and fills the high pressure chamber. Excess fuel flows out through return flow channel 5. In the discharge phase (b) the plungers 1 with the needle closed 4 move on the ascending profile of the cams to the axis of the shaft-distributor, increasing the pressure in the high-pressure chamber. High-pressure solenoid valve 7 is built into high-pressure circuit of HPF for metering of cycle feeding. To the high pressure solenoid valve on a signal from the control unit of the fuel injection pump, voltage is applied to the solenoid coil, and the armature moves the needle. pressing it to the seat. If the needle is pressed against the seat, the fuel flows only to the high pressure outlet 14 connected to the discharge valve 15, where the pressure rises sharply, and from there to the nozzle. Fuel dosage is determined by the interval between the moment of the beginning of the feed and the moment of opening of the solenoid valve and is called the duration of the feed. The closing time of the solenoid valve, determined by the control unit, thereby controls the amount of cyclic fuel flow. When injection is finished, the valve solenoid is de-energized and the high pressure solenoid opens and the pressure in the circuit is reduced, stopping the supply of fuel to the nozzle.
the combustion process is most favorable and the best efficiency of a diesel engine is ensured only when the moment of beginning of combustion corresponds to a certain position of the crankshaft or the piston in the cylinder. The purpose of the injection advance device is to increase the fuel start angle when the crankshaft speed increases. The device, consisting of an injection timing sensor, control unit and solenoid valve to set the injection timing, provides the optimum injection timing for the engine operating conditions and compensates for the time delay determined by the shortening of the injection and ignition period when the rpm increases.
The hydraulically driven injection advancement device is installed on the bottom of the housing across the longitudinal axis of the fuel injection pump.
Injection advancement device:
1 cam washer; 2 ball trunnion; 3 pilot advance angle setting plunger; 4 underwater/outlet¬Fuel output; 8 fuel inlet; 9 supply from the fuel system; 6 control valve; 7 fuel outlet; 8 fuel inlet¬The plunger is equipped with a control spring¬In the axis of plunger 3 there is a springloaded control piston 12, which sets the position of the control valve; 11 a return spring; 12 the control piston; 13 an annular chamber of the hydraulic¬In the middle of the plunger is the control valve 5 which opens and closes the control holes of the plunger stop; 14 throttle; 15 solenoid valve for setting the injection start torque (in the closed position)
Cam washer 1 enters with its ball stud 2 into a cross hole of the plunger 3 so that progressive movement of the latter turns into rotation of the cam washer. In the middle of the plunger there is a control valve 5, which opens and closes control holes in the plunger. Located along the axis of the plunger 3 is a spring loaded control piston 12, which sets the position of the control valve.
Across the plunger axis there is the electromagnetic valve 15 to set the injection start moment. The HPF control unit acts on the plunger of the injection advance device with the help of this valve, to which current pulses of constant frequency and variable frequency are continuously supplied. The valve changes the pressure acting on the control piston.
The solenoid valve sets the timing of the injection start:
1 valve seat; 2 closing direction; 3 valve needle; 4 solenoid armature; 5 coil; 6 electromagnet.
“Disassembling” the Opel Frontera: Bosch VP44 fuel pump and other troubles 2.2 DTI
By the example of Opel Frontera we decided to find out the weak points of popular Ecotec 2 diesel engine.2 DTI and its fuel system.
This example of the 2000 Opel Frontera B has already been in our “Disassembly” column. Let’s remind: at that time the oil pump was changed. the car was bought under the principle “live body, live frame, but questions on the engine”, so the appearance of problems is not surprising. This time there was a problem with the fuel system. They were worked on together with a specialist workshop foreman.
While replacing the fuel filter, there was water in the plastic case! And the present owner refuels only at gas stations, but what was before it. a secret We cleaned the tank, changed the filter and literally the next day the engine stopped “pulling”, began to twitch, no higher than 2500 rpm, “fell” into the emergency mode. the owner continues Barely made it to the service station. The specialists’ verdict. it is necessary to disassemble HPF, as well as to look for “air inflow”. I thought about the option of buying a used fuel pump. its cost ranges from 450 to 800 depending on the version. but the warranty on the repaired pump was given for one year. So it was decided to send the Bosch VP44 for repair.
The fuel sample from the tank of a similarly equipped Opel Zafira that was in the same service station. The owner states that he buys fuel only at gas stations. Moisture in the pump and mechanical wear and tear are the main causes of failure of the fuel injection pump
As a result the problem was solved by pump body repair, replacement of fuel injection regulator piston, cleaning all technological channels and installation of repair kit. The problem with “sucking” air included replacement of return tubes, washers under the injectors. As a result, the whole event. repair of HPF and elimination of “sucking air”. cost 600 to the owner.
Bosch VP44 pump lifetime can be increased by adding in fuel tank of two-cycle oil. 100-150 grams per 20 liters is enough. But the service life of fuel injection valve mostly depends on the timely maintenance and filling the car with quality fuel
What are other problems with the VP44 HPF?? Yegor Alesin told about them some time ago. The control processor of the Bosch pump may break down because of overheating. At the same time the engine is starting to malfunction intermittently. But more often the diesel engine either just stops working and does not start anymore, or does not start after parking. In these cases the ECU usually fixes an error in the “brains” of the fuel injection pump. In the “original” fuel injection pump is supplied only as a complete unit, but there is an option to buy a reconditioned pump at the factory or used. There are also some workshops in Minsk, where they successfully restore the ECU of the fuel injection pump, using components of the domestic military-industrial complex in its electronic circuit. “VP44 HPF also have mechanical failure, as we have already learned. the injection regulator piston seizing due to the use of low-quality fuel. The owners should closely watch the quality of fuel and do service in time.
Second problem of engine 2.The 2 DTI consists of the EGR system, the valve of which may eventually need to be replaced. Exhaust Gas Recirculation. a system of exhaust gas recirculation, it is necessary for reducing the content of nitrogen oxides in the exhaust gases of internal combustion engines. EGR valve. a device for metered regulation of the amount of gases for recirculation.
Emulator completely simulates EGR valve operation from ECU point of view, error on non-operational valve is not fixed
Also, thanks to Exhaust Gas Recirculation. a mechanism for relieving part of the exhaust gases back into the combustion chamber. soot is abundantly deposited on the walls of the intake manifold channels. The Frontera owner decided to prevent future problems by installing an EGR emulator.
The formation of soot in the intake manifold channels is the result of the exhaust gas recirculation system
Rostislav not only repairs Opel but also drives himself Frontera B with Ecotec 2 engine.2 DTI. He knows it very well Ecotec 2 chain engines in general.The 2 DTI in different modifications are quite reliable if properly and timely serviced. But there are some disadvantages. There are possible problems with EGR valve and chain breakage of balancer shafts. Always visit a trusted charging station to avoid problems with the pump VP44. Yury GLADCHUK Photo by Pavel SLEPUKHIN ABW.BY
Simplified scheme electronic regulation
The Bosch single plunger fuel pump type VE for the diesel engine is shown in figure 4.
Figure 4. Schematic diagram of the electronic control system of single plunger fuel injection pump:
1. injection start sensor; 2. TDC and crankshaft speed sensor; 3. air flow meter; 4. coolant temperature sensor; 5. fuel pedal position sensor; 6. control unit; 7. gas pedal actuator for starting and warming up the engine; 8. Exhaust gas recirculation valve control servo unit; 9. Injection advance angle control servo unit; 10. Dispense clutch servo unit; 11. Dispenser stroke sensor; 12. Fuel temperature sensor; 13. HPF
The main regulating element of the system is the electromagnetic actuator 10 which moves the dosing clutch of the fuel injection pump.
The fuel supply processes are controlled by the control unit 6. The control unit receives information from various sensors: the beginning of injection 1, installed in one of the fuel injection nozzles, the top dead center and crankshaft speed 2; air flow meter 3; coolant temperature 4; fuel pedal position 5, etc. In accordance with the control unit memory and the information received from the sensors the control unit outputs signals to actuators controlling cyclic delivery and advance angle of fuel injection. Thus, the value of cyclic fuel supply is regulated from idling to full load mode, as well as during cold start.
The potentiometer in the actuator sends a feedback signal to the electronic control unit to determine the exact position of the metering clutch. The advance angle of fuel injection is controlled in a similar manner.
The electronic control unit generates signals ensuring flow of regulating characteristics, idling speed stabilization, exhaust gas recirculation, the degree of which is determined by signals from the mass air flow sensor. The control unit compares the real sensor signals with the values in the programmed characteristic fields, resulting in an output signal to the servomechanism of the actuators, which provides the desired position of the metering clutch with high regulation accuracy.
The system is based on the program of self-diagnostics and working out of emergency modes, which allows providing movement of the car in case of the majority of failures, except for the microprocessor failure.
In most cases for single plunger pumps of directional type as an actuating device regulating cyclic flow uses electromagnet 6 (Fig. 5) with a rotating core, the end of which is connected through the eccentric to the metering coupling 5. When current flows through the solenoid coil, the core rotates by an angle from 0° to 60°, respectively moving the dosing clutch 5, which changes the cyclic feed rate.
Fig. 5. Single-plunger pump with electronic control
1. fuel injection pump; 2. automatic advance-injection advance control solenoid valve; 3. nozzle; 4. automatic advance-injection advance control cylinder; 5. dosing unit; 6. electromagnetic device for change of fuel supply; 7. electronic control unit; 8. temperature, boost pressure, fuel supply position sensors; 9. control pedal; 10. fuel return; 11. fuel supply to the injector
Control of automatic advance injection is performed by quick-acting electromagnetic valve 2, which regulates fuel pressure acting on automatic injector piston. The valve operates in pulse mode “open. close”, modulating the pressure depending on the speed of the engine shaft. When the valve is open, the pressure decreases and the advance angle of injection also decreases. When the valve is closed, the pressure increases, moving the automatic piston to increase the advance angle of injection. When the valve is closed, the pressure increases, moving the piston of the automatic gas burner control valve towards the higher valve opening angle. One of the injectors is equipped with an inductive needle lift sensor to detect the moment of the start of injection.
Proportional electromagnetic, torque, linear or step motors are used as actuators acting on the organs controlling fuel supply to the fuel injection valve, which serve as a direct drive of a fuel dosing device in pumps of a distribution type.
As an example, Figure 6 shows the actuating mechanism that controls the fuel supply, which uses an electromagnet 2 with a rotary core, the end of which is connected through the eccentric to the metering clutch 3. When current flows in the coil of electromagnet core rotates by angle from 0 to 60°, respectively moving metering clutch. Its movement is monitored by means of a sensor 1.
Fig. 6. Electromagnetic actuator of fuel injection pump of distributive type
1. sensor of dosing unit stroke; 2. actuating device (electromagnet); 3. dosing clutch; 4. valve of change of angle of beginning of injection with electromagnetic drive
The fact that the advance of fuel injection for diesel engines is very important, nobody needs to explain. Naturally, for each engine speed some specific value of advance angle will be optimal, for example, for idle speed 800 rpm. 3°, 1000 rpm. 4°, 1500 rpm. 5°, etc.д. To achieve this relation, which is not linear, there is a special mechanism in the housing of the fuel injection pump. However it is just a piston (sometimes in literature it is called a timer) which moves inside fuel injection pump by fuel pressure and with the help of special lever turns a special washer with wave profile by this or that angle. If the piston is retracted further, the wave of the washer will run a little bit earlier on the plunger, it will start moving and supply fuel to the injector earlier. In other words, the injection advance angle depends on fuel pressure inside the fuel injection pump housing and on the degree of wear of the wave profile of the washer. As a rule there is no problem with fuel pressure. Unless the fuel filter gets clogged, the reducing valve plug gets jammed or the feed pump blades (inside fuel injection pump) get stuck.
All of these problems are quite rare and easy to calculate. It is possible to estimate a condition of the fuel filter easily and unambiguously, if to transfer the engine on an external power supply, that is to put a plastic bottle with diesel fuel under a cowl and to disconnect pipes of fuel injection pump and “return” from the regular places and to put in this bottle. After that start the engine and check its operation. It is even possible to drive several kilometers. If there is no change in the engine, the fuel filter and everything around the fuel tank is fine. By the way, if you add 30-50% of any engine oil into a fuel bottle, the HPF will be forced to supply thicker fuel (mixture of diesel and oil). And if there is some wear in fuel injection pump (for example, plunger pairs), this wear would affect to a lesser degree, and the engine would work better. For example, it is very hard to start the engine when it is hot. the reason is often the insufficient amount of fuel supplied due to wear of the main plunger pair. And if with thick fuel this defect (hard starting) almost disappears, you can confidently take off the fuel injection pump and replace it with a worn pair. Although in that case you usually need to replace everything in the fuel pump, and it’s easier to throw it out than to repair and adjust it. However, it has already been written about it above.
State of pressure reducing valve (can be in a wedged state) and fuel feed pump can be estimated, using the manual fuel priming pump. If the engine changes after you start pumping with the hand pump running, t.е. If you start to raise the pressure in the housing manually it means that either the valve or the pump is defective. The pressure reducing valve can be easily unscrewed without removing the fuel injection pump and checked. Only on most diesel engines, you have to remove the corner of the bracket with a thin chisel, and then the head of the reducing valve becomes accessible to a special wrench. By the way, the reducing valve can be removed with a long chisel, without using a wrench.
All seals there are made on rubber rings (toriqs) and do not need to be tightened too much. If this valve is intact and the plunger is not jammed in the open position, the feed pump should be suspected. Provided that when you pump the fuel the engine runs smoother. It is true, if there is fuel with air bubbles coming out of overflow line (return) when the engine is running, then first of all it is necessary to remove the air drain. Because if there is air inflow, it is difficult to create the required pressure in the HPF, even with a completely functional pump. But the problem with the air suction. is a separate issue. Here we just note that the air inflow, even with an external power supply, t.е. when the fuel canister is above the fuel injector, it is possible through the fuel injector packing and through not tightness of the central plug on the cast iron part of the fuel injector. This plug is used for precise positioning of HPF on the fuel feed angle (it is unscrewed, a micrometer head is installed and plunger stroke is measured, this procedure is described in almost all repair manuals for HPF). With a fully functional HPF, even if it was previously clogged, after 10 minutes of engine operation in the overflow line there are no air bubbles.
So, the advance injection angle depends on the engine rpm. To save fuel, achieve high power and for the environment, it is better to change this advance angle while taking into account other engine operation conditions, such as engine load, boost pressure, temperature etc. But it is possible to take into account all these conditions completely only for the electronically controlled HPF. Conventional mechanical units have only fuel pressure in the fuel pump housing and, on more modern units, the engine coolant temperature. The piston in the lower part of the fuel injection pump moves depending on the fuel pressure and through a special steel “finger” slightly turns the profile washer (the same washer is forcibly turns the driver from the heating device mechanism). As a result, the wave slip of the washer collides with the ram and the ram starts moving earlier. This whole system was calculated and made at the factory and more or less coped with its duties. Before heavy wear and tear begins. It became intensive, because in fuel injection pump began to receive unlubricated fuel (our “dry” winter fuel, just like kerosene, almost does not contain heavy fractions, which provide lubrication of all rubbing parts), fuel with air and just dirty fuel (with abrasive). However, ordinary old age does its work, too. As a result the shoulder on the washer starts to run against the plunger a little later and the latter in turn starts a little later its movement. In other words injection starts a little bit later. The beginning of the phenomenon looks like this. The engine idles and, due to different nozzle wear, shakes a little. Then we give it a little more rpm. At about 1000 rpm the engine stops shaking and sort of freezes. runs smoothly. smoothly. Increase revs even more. Suddenly there is a shudder in the 1500. 2000 rpm range. The jerking motion can appear either with a smooth, but intensive or a slow RPM boost. Blue smoke coming out of exhaust pipe during shaking. When the engine is fully warmed up, the shaking around 1500. 2000 rpm disappears. This is at the beginning of the defect development. Then the shaking does not disappear even after the engine warms up. Exactly the same shaking occurs if you raise the injection pressure at the injectors. In that case, if the fuel injection valve is worn, you’ll also get delayed injection. We get rid of this phenomenon by turning the fuel injection housing to an earlier injection. Sometimes you have to turn the fuel pump almost all the way in. But before you do that, listen to the engine. When a diesel engine is injected too early, it starts to run harder (they also say that the valves are knocking). And if you make sure that at about 50-100 rpm before the beginning of shaking this rigid component in the acoustic background of the diesel disappeared, it means that it is exactly necessary to turn HPF. It should be noted that in worn diesel engines the piston-cylinder gap is very big, so they start to run rough, even with a perfectly correct advance angle of injection. Using a stroboscope to set the advance of injection in our case is not really justified. Let’s not talk about the fact that stroboscopes more confidently catch with their microphone knocking already heavily worn injectors. If the injector is in decent condition, however, and the fuel tube is properly attached, the strobe light will usually fail. The stroboscope can be used to set the advance of the injection at idle speed. This is the advance angle which is given in the datasheet. But the wear in the fuel injection pump is uneven. And very often by setting the timing with a stroboscope at idle, we do not get rid of the jolting at idle caused by a late fuel supply. That’s why we recommend that you set the timing by ear. With the wear that the diesel engines we operate, this is a more acceptable way. This is the only way to compensate the late injection, caused by low fuel pressure in the fuel injection pump housing due to the feed pump wear. It is almost the same as the ignition advance setting for gasoline engines. You can set the ignition advance only at idle rpm with the help of devices (and the other is not suggested by the repair manuals), but because of a failure, for example of the centrifugal regulator, the car will not move. Obviously, it has to be repaired or replaced. But it is possible, by turning the timing switch, to set an acceptable ignition advance angle by ear. The only difference is that for gasoline engines, the criterion for proper ignition timing without the use of instruments will be detonation knocking and engine power, and for diesel engines. shaking, smoke and knocking in the engine.
As already mentioned above, most problems with fuel injection pump occur because of all kinds of leaks. For example, the plunger is worn out, there is a leak, and it doesn’t create pressure. And if you change the fuel to a thicker one.? Then the increased clearances in the mating parts will seem to get smaller. And the fuel injection pump will run like it’s not even worn at all. It’s very easy to make the fuel thick. Add, as stated above, any engine oil to it. Of course, you don’t want to drive like that. it’s too expensive (and it’s a hassle to constantly prepare thick fuel). But to check the condition of the fuel injection pump (as well as for the successful sale of a heavily used car at the bazaar) this technique is useful. In the cold season, due to a natural laziness, in order to make the fuel thick, we simply cool the HPF. For example, a car with a diesel engine comes with the complaint that it does not start if it stands for five minutes, but the engine is still hot. We start this car (really, sometimes we have to twist the starter for about 30 seconds), warm it up for another 10 minutes and turn off. After that we open the hood and cool the HPF with snow. Within the same 5 minutes. If after this operation the engine starts better than the first time, it is already possible to talk about heavy wearing of the HPF. Of course, both these tricks (with thick fuel and with cooling the fuel injection pump) are not described in the factory engine repair manuals and, therefore, they cannot be considered very scientific. In those manuals is measured the volume of fuel flow at startup (there is such parameter in technical data. volume flow at 200 rpm) and to check this parameter at home is also not difficult. To do this, it is necessary to unscrew all glow plugs and remove the tube from one injector. Then we put on this tube the body of a disposable medical syringe and twist the engine with the starter. Naturally, counting the “squirts.”. 200 “squirts” is certainly a lot. 50 is enough, and then compare the result with the technical data. In this case, you can assume that the injection volume at 200 rpm for all Japanese diesel engines, if they have the same volume, will be the same. If your engine volume is a bit different, it is not difficult to make a proportion with the volume of diesel engine, for which you have data. All this we also do, when a hot engine does not start well, though, as practice shows, it is possible to check everything easier. Using snow and engine oil. In other words, if the operation of fuel injection unit with thick fuel becomes more acceptable, it is necessary to check the injection volume. It is better, of course, to do it all on the bench (there you can check all operating modes of the fuel injection pump), but in the start mode (i.e. in the engine starting mode), the engine fails in a short time because the rubbing parts work dry and overheat.е. at 200 rpm) check can be done in the garage.
So, if the diesel engine has a shaking around 1500. 2000 rpm, accompanied by blue exhaust fumes, it is necessary to repair the fuel system. And in particular, to make fuel injection earlier. To do that, in the simplest case, you need to turn the fuel injection valve to an earlier injection.
Kornienko Sergey© Legion-Avtodata Diagnosti g. Vladivostok