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Symptoms of insufficient engine power: It is reflected in the acceleration performance and climbing ability, especially in the case of heavy load, the engine power is obviously insufficient, the accelerator is soft, and the speed of the vehicle cannot be increased rapidly; the exhaust is dull, the driving is weak, and the fuel consumption increases linearly… Sudden and strong, usually mainly rely on the driver’s feeling to judge.

The following introduces the causes of insufficient power and troubleshooting methods:

01

The “gas” problem

Intake system failure

Intake system: air filter – intake pipe – supercharger – intercooler – combustion chamber

(1) The air filter is clogged

The blockage of the air filter causes the intake resistance to increase and the amount of air entering the cylinder to decrease, resulting in incomplete diesel combustion and insufficient engine power.

Maintenance suggestion: Regardless of whether the air filter is wet or dry, the air filter core should be cleaned frequently or the dust on the paper filter element should be removed, and the filter element should be replaced if necessary to ensure that the air filter is clean. In spring, there are many willow catkins in the air, which can easily block the filter element. It should be checked more and cleaned up in time.

(2) The connecting pipes of the air system are worn and the joints are loose

The supercharged diesel engine relies on the exhaust pressure to blow the turbine to drive the pump wheel to rotate at a high speed and deliver compressed air to the intake duct. Guaranteed engine power. Therefore, the intake and exhaust systems of supercharged diesel engines must be completely sealed. If the exhaust pipe or joint leaks, the exhaust pressure will drop, the speed of the supercharger will drop, the intake pressure of the engine will decrease, and the engine power will naturally drop. If the air intake system includes the intake duct, the inter cooler and the joints, if the air leaks, then although the intake pressure provided by the supercharger meets the standard, the amount of air that actually enters the engine will be obviously insufficient, which will reduce the engine power.

This kind of failure also often occurs on new cars. After the new car has been running for a period of time, the pipeline will continue to expand and contract when exposed to heat, and the joints are easily loosened.

Maintenance suggestion: The driver should regularly check the pipeline and the connection, if there is any looseness and tightening; the new car should be compulsorily maintained after a period of use.

(3) Air cooling system

The inter cooler box and the water tank are adjacent to each other. Over time, the two components will interfere due to deformation and displacement, which is easy to cause the wear of the inter cooler box, resulting in air leakage and reduced air pressure.

Maintenance suggestion: The air leakage of the intercooler should be repaired at the designated service station of the OEM, and the intercooler should be replaced if necessary. Usually, the driver should check the inter cooler frequently, check the deformation and interference, and maintain it regularly.

02

The “diesel fuel” problem

fuel intake system failure

Fuel inlet system: fuel tank – fuel pump – primary filter – fine filter – fuel injection pump – fuel injector – combustion chamber.

(1) The diesel filter is blocked

The debris in the oil causes the diesel filter to be blocked, causing the diesel flow resistance to increase, the amount of oil entering the high-pressure pump to decrease, and the amount of diesel injected into the cylinder to decrease accordingly, resulting in insufficient output power of the diesel engine.

Maintenance suggestion: Check and clean the diesel filter element frequently, and replace it if necessary. The diesel filter should be replaced after driving 10,000-12,000 kilometers to ensure that the diesel filter is clean.

(2) The fuel inlet pipeline is blocked and the bend is dead

The low-pressure oil circuit is blocked or the diesel pipeline is bent, causing the oil circuit to be blocked and the diesel flow resistance to increase.

Maintenance suggestion: Check and re-install the low-pressure diesel pipeline, replace the pipe fittings if necessary, and ensure the diesel pipeline is unobstructed.

(3) Wear of the oil pump

The piston of the oil transfer pump is worn, resulting in insufficient pressure, small oil absorption, and the oil supply cannot keep up.

Maintenance suggestion: regular maintenance of the oil transfer pump

03

Problems with the electronic control system

The failure of the electronic control system leads to the lack of engine power, which has become a common sudden phenomenon, and there is no warning – any small problem such as poor wire contact, sensor damage, and excessive sensor gap may lead to failure.

Learn about:

Electronic control reasons

(1) The throttle position sensor is faulty. For example, the throttle valve is too dirty, the sensitivity is decreased, and the response is slow.

(2) The air flow sensor is faulty. If the detected data is inaccurate or there is fouling on the hot line of the air flow meter.

(3) The coolant temperature sensor is faulty. If the temperature of the coolant cannot be reflected correctly, an error signal is provided.

(4) The intake pipe pressure sensor is faulty. If the signal cannot be output, the computer keeps the engine running according to the preset signal, but the preset signal cannot be adjusted with the change of the vacuum degree, resulting in the deterioration of the engine performance.

(5) The crankshaft position sensor and the camshaft position sensor are faulty. If the speed signal cannot be transmitted correctly, it will cause the engine to ignite incorrectly.

(6) The Hall sensor is faulty. If the computer does not work well, the fuel injection time is too long. After the oxygen sensor detects it, the computer will reduce the fuel injection pulse width and make the mixture thinner, resulting in poor engine operation.

(7) Poor circuit contact. Such as poor contact of the connector terminals on the side of the injector wiring harness, poor contact of the ground wire, etc.

(8) Assembly errors.

Repair suggestion:

Power on self-check, the fault light will flash to show the fault condition. The driver is advised not to move, and if the vehicle can continue to drive, find a nearby maintenance station of the OEM to troubleshoot the problem. In addition, many drivers have the habit of flushing the engine with water, which should be avoided, because it is easy to cause the electronic control components around the engine to fail.

04

Problem with the engine itself

(1) Valve wear

After a long period of action and wear between the engine valve rocker arm and the valve, the gap will become larger and larger. If the gap is too large, the intake air volume will be insufficient, and the exhaust volume will be insufficient, which will affect the combustion and work of the diesel engine, resulting in insufficient power output of the diesel engine.

Maintenance suggestion: The valve clearance should be adjusted regularly to make it reach the specified value. Some drivers who understand maintenance can make adjustments by themselves. If you don’t understand, don’t tamper with it, and ask professional repairmen to help you adjust.

(2) Engine wear

There are sand and soil debris in the engine air chamber, poor oil lubrication, and high or low water temperature (normally 80~90 degrees Celsius), which will cause the piston ring and cylinder liner to wear and tear. Over time, the wear is too large, and the cylinder compression pressure will be low. , the fuel combustion is insufficient, reducing the effective output power of the diesel engine.

Maintenance suggestion: a comprehensive maintenance should be done when the vehicle travels 40,000 to 50,000 kilometers, and each part of the engine should be maintained.

Maintenance reminder: Poor fuel quality may also cause engine power failure. Vehicle diesel engines are required to burn diesel fuel with a cetane number greater than 45, and diesel fuel below this standard has poor combustion characteristics. Drivers should try to choose large regular gas stations to replenish fuel.

Track summary:

There are various reasons for the lack of power. In many cases, the problem of lack of power will disappear after the fault is eliminated. There are also times when there is no problem with the car itself, but the driver reports that the power is insufficient and wants to increase the power.

The problem of slow acceleration of the truck, and the driver’s unhappy driving, can be solved in two ways in the past:

The first is to adjust the fuel injector by the fuel injector test bench, increase the fuel injection volume of the fuel injector, generally increase the fuel injection volume of the pre-injection point, and adjust the fuel injection volume. This method is technically difficult and difficult to operate. Just blowing smoke.

The second one is to install a horsepower amplifier, which has obvious side effects, such as increased fuel consumption, smoke from the vehicle and even burn out the engine.

Firstly we introduce the different working conditions of the common rail injectors:

1) Full loading diesel fuel return: long power-on time, maximum rail pressure, fuel return, judge common rail injector sealing, whether there is enough diesel fuel supply capacity.

2) Full load fuel injection: long power-on time, maximum rail pressure, fuel injection quantity, determine the maximum fuel injection capacity of the common rail injector

3) Emission injection quantity: medium power-on time, medium rail pressure, fuel injection quantity, medium load determination, acceleration characteristic diesel fuel quantity of the common rail injector

4) Pre-injection quantity: short power-on time, medium-high rail pressure, fuel injection quantity, judge injector’s response ability, eliminate noise of the diesel injectors

5) Low idle  injection quantity: long power-on time, low rail pressure, fuel injection quantity, judge whether the starting and idle diesel quantity is qualified

a) Foreword: All shims inside the common rail injectors, if in contact with the spring, directly affect the spring force; if contact with other parts directly affects the fit clearance or stroke between the parts.

b) Intermediate shims (needle valve stroke)

When the adjusting shims is thickened, the stroke of the nozzle is correspondingly reduced, which is equivalent to the smaller opening of the nozzle, and the flow rate of the long power-on time is most affected (including the total load).

c) armature stroke shims

The shims is thickened, the corresponding position of the solenoid valve is increased, the lift of the armature is increased, and the amount of diesel fuel is increased accordingly, which affects the fuel quantity of all test points, and the test point of the short energization time is particularly obvious.

d) Buffer stroke gasket (overlift shims)

The gasket is thicker and the over-lifting is smaller. The gasket has no significant effect on the fuel quantity, but the excessively thick gasket may cause the armature core to not fall, which may affect the valve ball seal, and vice versa. .

e) Grease spring adjusting shims.

The gasket is thickened and the spring force of the nozzle spring becomes larger. Under the condition of lower rail pressure, the needle valve is more difficult to open and the diesel quantity becomes smaller. When the rail pressure is higher, the spring force is much smaller than the upward force of the needle valve, and the influence can be neglected. Therefore, at low idle points, the diesel quantity has an obvious influence.

f) Solenoid valve spring adjusting shims

The shims is thickened, the spring force of the solenoid valve becomes larger, the armature response is more difficult, the response speed becomes slower, the diesel fuel quantity becomes smaller, and the fuel quantity at the discharge point is mostly affected.

The video is a demstration of stage 3 repair skill:

https://www.youtube.com/watch?v=lgfn2meNmPw

The necessary conditions for BOSCH common rail injector to start fuel injection.

The necessary conditions for BOSCH-common rail common rail engine injector to start fuel injection

Common rail pressure exceeds the minimum set value (>350bar)

Synchronization signal is normal:

Sensor signal ≥ trigger threshold (related to air gap and speed)

The phase is correct

1: Check whether the rail pressure sensor is normal

Unplug the rail pressure sensor and check the rail pressure sensor harness end with a multimeter: 5V between 1-2, 5V between 1-3 is normal, or you can use a pin of multi-meter to connect 2 holes, another pin on the table,if 4.8. v is normal, the third hole, is about 4.8v is normal.

Note: 1 is the power ground, 2 is the signal, 3 is the power supply

Second, high idle speed

High idle speed means that only one speed is 1100 rpm after the engine is started, and the accelerator pedal is invalid.

High idle speed is generally caused by a throttle problem.

The throttle of the common rail engine is a double potentiometer type. Check the throttle line: the first voltage should be 5V, the second voltage is 5V normal; see the first signal voltage of the diagnostic scanner is about 2 times the second signal voltage which is normal.

If the first voltage is not 5V, it is 3.2V (the same voltage as the common rail). At this time, remove the rail pressure sensor, and the voltage of the throttle becomes 5V, indicating that the rail pressure sensor fails and the common rail assembly is replaced.

ECU damage determination

Reason 1: Lose self-test function; (Occasionally lost, everything else is normal, ECU also has bad possibility)

Reason 2: Accelerated abnormality;

Reason 3: Excluding all peripheral line faults, the problem cannot be solved. Consider the ECU internal program problem, the probability is very small.

Fourth, the parameters to be noted on the diagnostic instrument

Set rail pressure value

The difference between the actual rail pressure value and the set rail pressure value should be less than 200hpa, otherwise stated

Actual rail pressure

Synchronization status

The starting instant sync signal should fluctuate between 3-48, and finally 48 means signal synchronization.

Cycle fuel injection

Rail pressure control integral

When the idle speed is between -2000 and +2000 is normal; less than -2000 indicates that the pipeline is blocked or leaking, the diesel is not smooth; more than 2000 indicates the injector, backflow pipe leak.

Rail pressure closed loop state

Torque limit state

Cooling water temperature

Pressure after intercooling

After cooling

Description of rail pressure: When the actual rail pressure value is less than the set rail pressure value of 200hpa or more, the fault code is reported:

P1011 rail pressure closed-loop control mode fault 0–the rail pressure is lower than the target value; this fault may be reported as an instant, then the fault will disappear when the difference between the two is within the allowable range.

The cause of this failure is a low (slight) blockage of the low pressure circuit (most likely the fuel filter is clogged)

The rail pressure cannot be established, ie the engine cannot start. There are two possibilities that rail pressure cannot be established: one is that the low-pressure fuel circuit is blocked or leaked, and the other is that the high-pressure fuel circuit is leaking (due to the difference in fuel content, the water content may cause the cylinder injector to become stuck, which may cause high-pressure fuel. If the leakage causes the rail pressure to be unable to be established, it cannot be started. The method can be judged; the fuel return of each cylinder can be checked and compared to determine whether the injector is good or bad. A historical fault code may be displayed from the diagnostics at this time:

P1014 rail pressure control deviation fault—mode 7, rail pressure control deviation fault—mode 10.

◆ Rail pressure closed loop state: 0 represents open loop state, 3 represents no diagnostic closure, 5 represents closed state, and 14 represents stomping state

◆Torque limit status

Bit 0: Engine Torque Limit in Error Status Bit 1: Maximum Torque Limit

Bit 2: Maximum Speed Limit Bit 3: Smoke Limit

Bit 4: Oil limit in error state Bit 5: Thermal protection limit

Bit 6: Drive Torque Limit in Error Status Bit 7: Transmission Torque Limit

Bit 8: Pump Balance Maximum Torque Limit

◆ Synchronization status (the number of the synchronization signal greater than 12 is less than 48 is garbled, 48 is the synchronization state)

Rail pressure release valve opens

If the engine accelerates up to 1700 rpm, and the fault light is on, the fault code read out is: the rail pressure release valve is open. At this point, you can feel it by hand: you will find that the temperature of the common rail return line is 50 °C higher than the temperature inside the common rail. At this time, the rail pressure in the common rail is a constant value of 720,000hpa!

Remedy: After turning off the key switch, turn off the whole vehicle for 20 seconds or even a few minutes, then turn on the power of the whole vehicle, turn on the key switch to start, the rail pressure release valve should be reset, and the starting is normal.

There are two possibilities for the opening of the rail pressure relief valve: the fuel metering valve on the high pressure pump is open and the return line is blocked. If these two conditions exist, the bleed valve cannot be reset.

When it is not possible to start, try to open the fuel metering valve one or two times. When the fuel metering valve is opened, the high pressure pump is equivalent to the mechanical pump. At this time, the rail pressure relief valve is opened. If the valve is opened more times. If it is too much, it will not be automatically reset. It is equivalent to the failure of the rail pressure relief valve. It is necessary to change the common rail. Therefore, generally do not pull the fuel metering valve.

How to read the fault code through the fault indicator

The ignition switch is ON → standby and operating conditions can be carried out → (for the diagnostic request switch is the automatic reset switch) press – release the diagnostic request switch; (for one open and close and then press back) can be activated Flash code → only one fault code is flashed for each operation, and all the fault codes can be read in sequence; the corresponding fault can be detected according to the fault code table;

How to manually clear the fault code?

When there is a fault in the engine, this method is generally not used. Once the fault code is cleared, the electronic control maintenance personnel can not find the cause of the fault when reading the fault code with the diagnostic instrument, it is difficult to take corresponding measures to repair,When the engine is all normal, you need to try this method when you need to clear the historical fault. Sometimes it can’t be cleared. It is best to operate it through the diagnostic device.

Specific operations:

Turn off the key switch for about 30 seconds → turn on the diagnostic request switch on the meter → immediately turn the key switch to the ON position → for 4 to 8 seconds → turn off the diagnostic request switch on the diagnostic request switch on the meter.

How To Test A Diesel Injection Pump ?

2 Operation requirements of the diesel pump test bench

2.1 Installation of the tested high pressure pump on the test bench

The high pressure pump is fixed to the table rail by special clamping devices. The front end of the high pressure pump is connected to the test bench universal joint via a coupling. When installing, it must be ensured that the high-pressure pump camshaft is coaxial with the test-table drive shaft, which can be achieved by installing a special pad between the high-pressure pump and the guide rail. After initial fixing, turn the universal joint dial 1 to 2 turns. When it feels smooth, tighten the large bolt and nut. After installation, the high-pressure pump should run smoothly and reliably, be firm and reliable, and have no jitter and looseness.

2.2 Start and stop of the diesel pump test bench

The pump test bench is connected to the three-phase power supply, and the speed control handle is turned to make it in the zero position. When the motor start button (green) is pressed, the motor can be started. When stopping, turn the speed control handle to reduce the dial speed to zero first, then press the stop button (red) to avoid stopping at high speed. The test bench will be damaged and an accident will occur at the next start-up.

2.3 Speed adjustment of the injection pump test bench

According to the required speed and direction, select the gear position of the gearbox, and turn the speed control handle to change the speed. The greater the deflection angle of the speed control handle, the higher the speed.

2.4 Pressure regulation of the fuel system for the injection pump test bench

The pressure of the fuel system is regulated by a pressure regulator. When the handwheel is rotated clockwise, the pressure can be adjusted within the range of 0 to 0.6 MPa, and the pressure can be adjusted within the range of 0 to 6 MPa when rotated counterclockwise. The pressure diesel fuel is sent from the fuel supply joint of the pump test bench to the high pressure pump under test through the fuel pipe.

2.5 fuel temperature control of the diesel pump test bench

When the fuel temperature is lower than 40 °C, turn the heating valve handle clockwise to increase the fuel temperature. When the fuel temperature reaches 40 °C, immediately close the heating valve to stop heating.

3 Maintenance and maintenance of the pump test bench

(1) In order to ensure the test accuracy of the pump test bench, the opening pressure of the standard injector should be checked frequently, which should be 17. 5 MPa; the uniformity of the standard injector should be checked regularly. If there is a difference, the opening pressure can be adjusted. Correction, if not correct, replace the standard injector.

(2) The test fuel must pass through the light diesel fuel which has been precipitated for more than 48 hours. It is necessary to replace the new fuel after commissioning 500 injection pumps or 400 hours of operation of the test bench. When changing diesel fuel, use kerosene to clean the fuel tank and filter. 30# or 46# turbine fuel is required for the transmission case and the hydraulic continuously variable transmission. Inject 40# mechanical oil or 150# mechanical oil into the gearbox. The oil level should not be lower than the oil-filled elbow, and it should be replaced every 400 h or half a year. The bearings in the tachometer seat should be lubricated with mechanical oil or turbine oil. When refueling, remove the mechanical watch and inject lubricant from the tachometer seat.

(3) Before starting of the pump test bench, it is best to use the lever to rotate the dial until the motor and fuel supply pump rotate at the same time, and then start the operation.

(4) Do not shift gears during the operation of the pump test bench or start the test bench at high speed, otherwise the hydraulic continuously variable transmission or gear will be damaged. When operating the speed control handle, slowly increase or decrease the speed, and do not operate quickly. When stopping, adjust the speed to zero to avoid damage to the transmission system and affect the service life of the injection pump test bench