Page 251 - CTS - Mechanic Diesel - TP

MECHANIC DIESEL - CITS

Do not run the pump.
Compare the readings of test bench manometer with the reference manometer at different pressures. If there is
any variation, replace or repair manometer or devise a correction table.

Caution: the comparison of manometer should be done only upto 3 kgf/cm² pressure. If the pressure control valve
is screwed in further, the manometer on the test bench is isolated by the pressure shut off valve. However, in the
pump gallery the pressure will build up to 45 kgf/cm² and damage the “Reference Manometer”.
Overcheck of Tachometer
Overcheck the tachometer with a hand tachometer. The variation should be within + 1.5% of full scale reading. If
more, devise / display a correction table or get the tachometer repaired.
OvercheckWith master pump
Check whether the seals on the master pump are intact.
Mount the master pump on test bench with a suitable coupling (maximum play permissible 0.5 mm).
• Connect high pressure pipes.
Maintain the test oil temperature at 40°C.
Vent out air from the master pump gallery. Run the pump for about 2 min, at 1000
min (rpm) maintaining the gallery pressure at 1 kgf/cm².
• Take 3 sets of readings at 1000 min¹ (rpm) and for 500 strokes. Record observations.
Note: Before taking each reading, ensure that the measuring glasses are wet and drained for 30
seconds.
If the average of the 3 readings is within the specified value the test bench is in order.
Specified value
25+ 0.5 cm³ for 500 strokes at 1000 min¹ (rpm)
Variation between cylinders should be within 0.5 cm³
If the average of 3 readings is not within the above specified values, the test bench needs rectification.
Example

Case Observed delivery quantity Remarks
I 24.0, 25.5, 23.0, 24.5, 26.0, 25.0 Erratic and not within specified value

II 24.5, 25.0, 25.5, 24.5, 25.5, 25.0 Within the specified value but variation between
cylinders is more than 0.5 cm³

Rectification
Check the test injectors for various functional parameters. Rectify, replace test nozzle if necessary and repeat
measurements.

If variation persists, change the high pressure pipes with new ones. Repeat measurements.
If variation still persists, Interchange high pressure pipes so that uniform values as close as possible are obtained.
If the observed delivery quantity is uniformly high or low:
Overcheck the tachometer.
Replace the test oil if it is suspected to be contaminated or too old.

Remove the high pressure pipes. Screw on adapters on master pump. Connect the other type of high pressure
pipes which were being used.
Take 3 sets of delivery values and record observations.
If the specified delivery quantity (25 ± 0.5 cm³) is not obtained, replace high pressure pipes.

• With the new high pressure pipes, if the specified value is not obtained or if the variation between cylinders is
more than 0.5 cm³ interchange high pressure pipes, without disturbing the test injectors.
In both the above cases the test bench needs rectification.

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CITS : Automotive - Mechanic Diesel - Exercise 15.1