Engine

Page 11

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Volvo Bus Service and Maintenance Manual

 Pump coupling discs and bolts
6 Check the bolt heads to see if the coupling shows signs of having been moved out of position. If it has, the advance-injection angle must be readjusted.
 
 Exhaust smoke
7 Check visually for the existence of exhaust smoke. If the exhaust smoke is abnormal, follow Notes 1 and 2 below.
 

Smoke density test

With abnormal black exhaust smoke, measure the density with a smoke density gauge.

The Bosch smoke density gauge uses replaceable filter discs in a suction pump which sucks up a specified volume of smoke from the engine's exhaust pipe. An evaluator then measures photoelectrically the extent to which the filter discs are blackened.

The density is measured with a fully loaded engine at approx. 1400 r/min. Otherwise follow the instructions of the manufacturers of the instrument.

The smoke density must not exceed legislated levels (varies for different markets).

Engine smoke test

Fuel injection timing

Engine fuel injectors

Note 1

Check/adjust the advance-injection angle only if the engine exhaust smoke is abnormal, if the engine performs poorly and/or if the pump coupling is loose.

Proper basic setting of the advance-injection angle is important for the combustion cycle in the engine and the fuel consumption. How to set the advance-injection angle is described in Service Manual, Section 2, Engine.

Injectors

Note 2

Check the injectors only if there are symptoms of abnormal exhaust smoke and low engine performance. The injectors are removed from the engine and tested on an injector tester. Opening pressure and tightness are most important. Spray pattern and chatter are more difficult to assess and do not provide any sure indication of the condition of the injector. Instructions on how to adjust the opening pressure after replacing injectors, thrust springs, etc., are to be found in Service Manual, Section 2, Engine.