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Injector Inspection Methods Using A Thermogun

Common rail-type fuel injection device injectors are located inside the head cover, and inspection (removal and installation of couplers, outside injection from cylinder) cannot be performed.An inspection method for mechanical problems (spray deficiencies, clogging, seizing) for which a diagnostic trouble code does not appear is necessary.

Judgment through temperature measurement

For engines in which combustion conditions are normal, the temperature of each cylinder will ordinarily increase. However, for cylinders in which there is trouble and combustion conditions are poor, it is difficult for the temperature to increase. Use these characteristics and observe the temperature change in each cylinder to judge whether there are cylinder problems.

The cause of the problem is often a defect (spray deficiencies, clogging, seizing) with the injector itself. Also investigate other causes and thoroughly perform trouble diagnosis before deciding what the problem is.

Difference in temperature change by state of combustion

Cylinders with low temperature have poor status of combustion. Therefore, you can judge that there has been some kind of trouble.

Complete combustion

Temperature Incomplete combustion

Hours

Thermogun

A thermogun is a infrared thermometer capable of noncontact temperature measurement. As a maintenance tool, this is sold as a thermogun and infrared thermometer. • Ideal for measuring temperatures from 0 ℃ to 500 ℃ . • Includes laser pointer • Includes spot measurement function (convergence ratio of about 10:1)

TSSA0004

Measurement preparation

Prepare the thermogun. Open the engine housing and check the exhaust manifold base measurement location. • Confirm that the measurement distance and angle of the thermogun are being kept constant. • This will cause measurement errors with each cylinder, so practice this when it will have no effect on operation. • The nearer the measurement distance is to about 30 cm, the more stable the measurement value will be. • If measurement data is recorded, it can also be used in customer explanations.

Measurement procedure

Start measurement with the exhaust pipe temperature at 100 ℃ or less. 1. Measure the initial status temperatures • Record the temperatures 2. Start the engine.Maximum speed/2 pump relief 3. Implement temperature measurement for cylinders 1 through 4 at a pace of about 30 sec. for 1 measurement • Record the temperatures 4. Repeat step 2 about 6 to 7 times. 5. When the temperatures get to about 400 ℃ , confirm that temperature increases are less sensitive. 6. After completing measurement, stop the engine after idling. 7. Narrow down the problem cylinder from the measurement values. • After 5 min. pass, it will become more difficult to determine the problem cylinder. • To perform measurement again, it is necessary to let the engine cool (below 100 ℃ ).

Judgment criteria

Rather than looking for an absolute value, judgment is done through comparing the temperature changes of each cylinder and finding the cylinder with a relatively low temperature change. The actual measurement values below are listed as reference data. Measurement temperatures vary depending on the measurement conditions, so see the data below as reference data for understanding general tendencies. In the typical measurement example, the following 3 measurements are listed. 1. Data during normal operation 2. When one of the cylinders on the end (number 1 or 4) is in an incomplete combustion stage 3. When a middle cylinder (number 3) is in an incomplete combustion state * Weather when reference data was obtained (outside temperature: 28 ℃ /weather: clear)

Work precautions

• Confirm that there are no people around the machine and perform work in a safe manner. • When measuring, be aware of the engine temperature. • Make sure to apply the swing lock.

[Tip]

During normal operation before the vehicle is delivered, measure and record the manifold temperature of all cylinders and keep this as judgment data for when a problem occurs.

Problem injector selection method

The comparison data below is test data for reference use.

Caution: Be aware that measurement values that differ from the test values may appear due to the actual test environment and main unit condition.

[During normal operation]

During normal operation, the same temperature fluctuation tendencies are present in all of the cylinders.

Test time #1 #2 #3 #4 0 21 21 21 21 40 51 55 55 55 1:10 170 169 174 199 1:40 265 256 250 272 2:20 304 324 302 334 2:40 328 342 328 358

[When the No.1 cylinder injection is stopped]

A marked temperature difference can be seen in comparison with the cylinders that are performing normal injection.

Test time #1 #2 #3 #4 0 56 60 66 65 35 57 135 193 193 1:00 61 165 246 255 1:25 66 187 288 312 2:00 74 208 305 341 2:30 77 217 332 345 3:05 80 221 346 367

[When the No.3 cylinder injection is stopped]

The cylinder fluctuates at a lower temperature range than the normally operating cylinders.

Test time #1 #2 #3 #4 0 81 91 105 101 30 127 180 128 245 1:10 202 297 145 275 1:40 233 332 206 311 2:20 263 367 206 342 2:50 294 365 253 354 3:25 297 398 253 369

[When the No.4 cylinder injection is stopped]

A marked temperature difference can be seen in comparison with the cylinders that are performing normal injection.

Test time #1 #2 #3 #4 0 101 100 85 56 40 136 159 130 60 1:10 224 241 170 65 1:40 252 295 200 70 2:20 320 333 243 74 2:40 331 340 255 80 3:25 380 398 260 95

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