Automobile Inspection Technology

Chapter 10 Automotive Engine Detection (6)
When the content of a certain metal particle in the lubricating oil suddenly increases, it means that there is abnormal wear of the friction pair in the engine, and it should be treated as an emergency.

Increased levels of silicon in the oil can indicate poor performance of the engine air filter and positive crankcase ventilation filter.

6. Ferrography analysis

The ferrographic analysis method is to separate the ferromagnetic metal particles from the lubricating oil with high-intensity magnetic field force, and deposit them on the ferrographic sheet (glass sheet) in sequence according to the particle size. , X-ray energy spectrometer or X-ray spectrometer, etc., to observe, measure and analyze metal particles to obtain the size, shape, composition and content of metal particles, and then analyze the cause, location and wear of metal particles degree.Therefore, ferrographic analysis can not only measure the degree of oil contamination by metal particles, but also is one of the important methods for engine diagnosis without disassembly.

(Section [-]) Engine Comprehensive Performance Test

发动机综合性能检测一般用发动机综合参数测试仪来进行。该仪器技术含量较高、检测项目齐全，可全面检测、分析、判断发动机在各种不同工况下的工作性能及技术参数，能对多种车型所存在的机械及电子故障进行全面的分析诊断，它在汽车综合性能及汽车故障的检测诊断中发挥着重要的作用。一般的修理厂、4S站及检测站都配有发动机综合参数测试仪。目前在国内汽车修理行业应用较广的发动机综合性能检测仪主要有德国的波许系列和国产的元征EA系列（包括EA-1000、EA-2000、EA-3000)、金德系列（包括K100、PC2000)等。

[-]. The structure, principle and characteristics of the detector
The engine comprehensive performance tester is also called the engine comprehensive performance analyzer, which generally consists of three parts: signal extraction system, signal processing system, acquisition control and display.Figure 2-41 shows the outline drawing of the domestic EA-2000 engine comprehensive detector.

1. Signal extraction system
The task of the signal extraction system is to pick up the parameter values ​​of the measured points of the car. In view of the different mechanical structures and parameters of the measured points, the signal extraction device must have various forms to adapt to different test locations.This system consists of some different shapes of plugs or probes, which can be divided into four types according to their different contact forms: the first type is direct contact type, which directly contacts the wire terminals of electrical components during measurement, such as for connecting The positive and negative poles of the battery and the alligator clips connected to the positive and negative poles of the ignition coil once, as shown in Figure 2-42.

The second category is non-contact.For example, the inductive or capacitive clamp is clamped on the ignition line of a cylinder and the high voltage line of the ignition coil to obtain the ignition signal.The starting current (high current) adapter shown in Figure 2-43 is actually a current transformer clamped on the battery line, which can induce the starting current.Because direct contact measurement of high voltage and strong current is extremely difficult, the above is the extraction of electrical parameters. For non-electrical parameters, a certain type of sensor must be used to convert non-electrical quantities into electrical quantities. This is the third category.For example, the electromagnetic TDC sensor provides the top dead center signal, the strobe light shown in Figure 2-44 can find the ignition advance angle, and the pressure sensor can convert the vacuum degree of the intake manifold or throat into electricity, and Figure 2-45 The thermistor in the temperature probe can convert parameters such as engine oil temperature and coolant temperature into voltage values.

The fourth category is aimed at electronically controlled fuel injection engines. Due to the needs of computer calculation of fuel injection pulse width and automatic control process, various non-electrical quantities have been directly converted into electrical quantities by sensors implanted in each system, and their extraction can be carried out through different conversion joints. Done, in order not to interrupt the control function of the computer, the signal must be extracted through the T-junction.

2. Signal processing system
The sensor assembled on the engine is a key component for engine control and engine fault judgment, but the electrical signals output by it vary widely, and cannot be directly used by the central controller of the vehicle-mounted computer or engine comprehensive performance analyzer, and must be pre-processed and converted into standard The digital signal is then sent to the computer.It attenuates and filters all the sensor signals of the engine
wave, amplify, and shape, and directly input all pulses and digital signals to the high-speed input terminal (HIS) of the central controller, or send 0-5V or 0-10V DC analog signals to high-speed instantaneous Change signal acquisition card.

3. Acquisition control and display system

Desktop and cabinet engine comprehensive performance detectors mostly use color CRT displays, while portable portable ones use small LCD displays.Now the analyzer can display the operation menu eye-catchingly, and display the current dynamic parameters and waveforms in real time. Set the display range and graph scale arbitrarily.

The acquisition card generally has a high-speed acquisition function, the sampling rate can reach 10Ms/s, the quantization accuracy is not less than 10bit, and there are 2 channels in parallel. It has a storage function for waveform retrieval and locked waveform for observation and analysis or output and printing.

[-]. Detection function and detection method

Now take the domestic EA-2000 automobile engine comprehensive performance tester as an example to illustrate the basic operation method of the instrument.

1. Preparation before the test
① Read the instruction manual of the instrument carefully before use.

②Before connecting the signal extraction system to the vehicle under test, turn on the power of the instrument to warm up for 20 minutes.

③ Connect the test line and sensor according to the instructions.Note that when connecting the test line between the instrument and the engine, the engine must be stopped and the ignition switch should be in the "OFF" position.

④Turn on the display switch of the power box of the instrument, the main unit enters the system self-test screen, the system will self-test each adapter one by one, if the connection is correct, it will be displayed in green, and if it is not installed, it will be displayed in red.

⑤ After the self-test, the system enters the user data entry interface, where the model, type, stroke number, cylinder number, ignition sequence, ignition mode, synchronization mode, rated power and other relevant data of the tested car are input.

⑥Click the "Confirm" button, and the system will enter the main menu of "Test Items".

2. Gasoline engine ignition system detection

(1) Primary ignition signal waveform detection

①Connection before detection:
The connection before detection includes the connection of conventional ignition system and direct ignition system.

a. Conventional ignition system.First, clamp the red and black clips of the battery voltage adapter to the positive and negative poles of the battery respectively, and then
The signal adapter clip of cylinder one is clamped on the high voltage line of cylinder one, as shown in Figure 2-46.

b. Direct ignition system (including single cylinder and double cylinder independent ignition system).First, clamp the red and black clips of the battery voltage adapter to the positive and negative poles of the battery respectively, and then connect the probes of the primary signal and temperature adapter (1280401-1DIS) to the waveform output terminals of each cylinder in turn.

② Detection steps:
Click the "primary signal" button to enter the primary signal detection interface, and then start the engine to measure the primary ignition signal waveform.

b. Click the "Cylinder Number" button, and in the small window popped up by the system, you can choose to display the signal waveform of each cylinder or all cylinders once.

c. Click the "Display Adjustment" button, and in the small window popped up by the system, you can choose to display the signal waveform of each cylinder or all cylinders once.

d. Click the "Save Data" button, the system will save the current characteristic value to the database.

e. Click the "Save Waveform" button, the system can save the current interface waveform in the specified directory.

C. Click the "graphic print" button to print the graphic of the effective area of ​​the interface.

g. Click the "Help" button to enter the help system, and you can view the relevant correct and fault waveforms for reference.Click the "Back" button to return to the upper level "Gasoline Engine Inspection" menu.

(2) Secondary ignition signal waveform detection

①Connection before detection:
The connection before detection includes the connection of conventional ignition system and other ignition systems.

a. Conventional ignition system.First, clamp the red and black clips of the battery voltage adapter to the positive and negative poles of the battery respectively, clamp the red secondary signal and temperature adapter to the central high-voltage line, and clamp the one-cylinder signal adapter to the one-cylinder high-voltage line.

b. Other ignition systems.The wiring method is connected according to the requirements of the manual.It should be noted that the user must correctly input the number of cylinders of the vehicle under test, the ignition sequence and the number of the cylinder being triggered, and correctly clamp all the secondary signal clips or secondary signal sensing pieces, otherwise the waveform may not be displayed normally.

② Detection steps:
a. Secondary planar wave waveform detection.Click the "Secondary Signal" button under the "Gasoline Engine Detection" menu to enter the secondary signal detection interface (the default is parallel wave), and then start the engine to measure the secondary parallel wave.

b. Secondary parallel wave waveform detection.Through the secondary parallel wave, the whole picture of the ignition of each cylinder can be clearly seen, and the fault analysis and judgment can be carried out according to the comparison between the measured waveform shape and the standard waveform, so as to determine the cause and location of the fault.

Secondary overlapping waveform detection.Align the starting points of the ignition waveforms of each cylinder and overlap them all at a horizontal position, which is called overlapping waves. If the distributor cam of the contact ignition system is worn unevenly or the camshaft is severely worn, the waveforms will overlap poorly. Generally, the overlapping angle cannot 5% over the period.Click the "Waveform Selection" button on the secondary planar wave waveform interface, and select the "Overlapping Wave" icon in the pop-up window, and the system will switch to the overlapping wave detection interface.

d. Secondary ladder wave waveform detection.Click the "Waveform Selection" button on the secondary planar wave waveform interface, and select the "Staircase Wave" icon in the pop-up window, and the system will switch to the staircase wave detection interface.

(3) Detection of ignition advance angle

①Connection before inspection: Connect the timing light as shown in Figure 2-47.

②Testing steps: Click the "Ignition Advance Angle" button in the "Gasoline Engine Test" menu, and then start the engine.Align the timing light with the top dead center mark of a cylinder on the crankshaft flywheel or pulley, use the strobe light to detect the ignition advance angle, press the power button of the timing light, and adjust the potentiometer on the strobe light to make the flash phase front and back Move until the mark on the flywheel of the crankshaft is aligned with the zero point of the scale on the flywheel housing or the top dead center of a cylinder on the pulley is aligned with the indicator mark, as shown in Figure 2-47.The display shows the ignition advance angle value, as shown in Figure 2-48.

(4) Dynamic balance detection

①Connection before detection: Before detection, the signal adapter of one cylinder needs to be clamped on the high-voltage line of one cylinder, and the primary signal and temperature adapter should be clamped on the ignition coil (red positive, black negative)
② Detection steps: Click the "Power Balance" button in the "Gasoline Engine Detection" menu to enter the power balance detection state.Click the "Detect" button, the system will issue instructions to make each cylinder turn off the fire in turn and automatically measure the speed drop when each cylinder does not work, and display them in turn.As shown in Figure 2-49, the interface shows the conditions of each cylinder before and after cylinder disconnection in a bar graph. The upper figure is the speed before cylinder disconnection, and the middle is the speed after cylinder disconnection. The larger the drop, the better the performance of the cylinder.

Note: Do not perform this operation for a long time on a car with a three-way catalytic converter to prevent catalyst poisoning.

(5) Cylinder efficiency detection

①Connection before detection: clamp the secondary signal and temperature adapter and the primary cylinder signal adapter to the corresponding high-voltage line.For the connection methods of different ignition forms, refer to the connection of the secondary signal.

② Detection steps:
a. Click the "Cylinder Efficiency Analysis" button in the "Gasoline Engine Detection" menu, and the system enters the detection state.As shown in Figure 2-1.

b. Click the "Detect" button below, the system will start to detect, and display the difference between the engine speed and the relative average speed of each cylinder.If the histogram is positive above the marking line, it means that the instantaneous speed is higher than the average speed, that is, the cylinder is working well; otherwise, if the histogram is below the marking line, it means that the working performance of the cylinder is relatively poor.

(6) Starting current and voltage detection

①Connection before testing: before testing, the starting current adapter must be clamped on the motor current line connected to the battery (the direction of the starting current adapter arrow should be the same as the current flow), as shown in Figure 2-50.Connect the charging voltage probe to the positive pole of the car generator, clamp the red clip and black clip of the battery voltage adapter to the positive and negative poles of the battery respectively, and clamp the charging current adapter to the charging current line connected to the battery [charging current ( In the illustration of this book, it is said that the direction of the arrow on the "small current" adapter should be the same as the flow of the current], as shown in Figure 2-51; clamp the signal adapter of a cylinder to the high voltage line of a cylinder.

② Detection method: Click the "start voltage, start current" button in the "gasoline engine detection" menu to enter the start voltage and start current detection interface.Click the "Detect" button to start the engine, and the system can automatically detect the starting voltage and starting current waveform and display the current engine speed, battery voltage, starting voltage and starting current.

(7) Charging current and voltage detection

①Connection before detection: the connection is shown in Figure 2-51.

② Detection steps:
a. Click the "Charging Voltage, Charging Current" button in the "Gasoline Engine Detection" menu to enter the charging voltage and charging current detection interface.

b. Click the "Detect" button, the system can automatically detect the charging voltage waveform and display the current engine speed, battery voltage value, and charging current value.

(8) Detection of relative cylinder compression pressure

The engine cylinder compression pressure is an index that marks whether the valve and piston are well sealed. It is not easy to obtain its specific parameters when the engine is not disassembled. It is only possible to detect the relative cylinder compression pressure change by detecting the starting current. For each cylinder compression pressure balance judgment.

①Connection before detection: The adapter connection method is the same as the starting current detection.

② Detection steps:
a. Click the button "Enter Relative Cylinder Compression Pressure" under the "Gasoline Engine Detection" menu to enter the detection interface.

b. Click the "Detect" button and the system enters the detection state; if the car has been started, a dialog box will pop up, prompting the user to turn off the engine first.

c. Start the engine, and the system will automatically display the engine starting speed, battery voltage value, relative cylinder compression pressure histogram and starting current waveform after the system is detected, as shown in Figure 2-52.The peak value of the starting current of each cylinder is marked above the starting current waveform in the coordinate system on the right, and the histogram of the percentage value of the relative cylinder compression pressure is on the left.

(9) Intake manifold vacuum detection

①Connection before detection: Before detection, check the advance angle and the relative cylinder compression pressure in Figure 2-52 of the intake air.

(10) Temperature detection

①Connection before testing: Insert the temperature probe into the intake pipe port, engine oil dipstick port and radiator port respectively.

② Detection steps:
(End of this chapter)