Exhaust Smoke - Detroit Diesel MBE 900 Technician Manual

PRELIMINARY
Fuel Temperature and Pressure (If data is erratic, take a snapshot.)
NOTE:
Record vehicle specifications in the event there is a need to predict vehicle performance
using Spec Manager.
Record crankcase pressure at high idle. DDC maximum specifications are:
For the MBE 4000 engines, the maximum is 0.37 kPa (1.5 in. H
engines (1998) and 2.0 kPa (8.0 in. H
For the MBE 900 engine, the maximum is 0.37 kPa (2.5 in. H
engines (1998) and EGR engines (2004).
1.3.5

EXHAUST SMOKE

The basic questions to ask for Black Exhaust Smoke are:
NOTE:
Black Smoke is soot from partially oxidized (burned) fuel at high temperatures.
Is the air filter restricted? (Reduced air flow = lack of oxygen, incomplete/high temperature
combustion and soot)
Are exhaust brake devices functioning properly? (Reduced air flow = incomplete
combustion and soot)
Is the CAC cracked? (Reduced air flow = incomplete combustion and soot)
Are the intake air manifold gasket(s) leaking? (Reduced air flow = incomplete combustion
and soot)
NOTE:
The MBE 4000 uses multiple air manifold gaskets to cover individual cylinder heads. The
MBE 900 uses one gasket for every two adjacent cylinders on a single cylinder head.
Are there air bubbles in the coolant? (Head gasket failure = vaporized water in exhaust)
Are there air bubbles in the fuel? (Fuel line/pump leak = late fuel injection = raw
vaporized fuel in exhaust)
Are the valve clearances correct? (Incorrect valve timing = incorrect combustion timing
and soot)
Is the comparative cylinder compression test result correct/within specifications? (Low
compression = incomplete/poor combustion)
Has a fuel nozzle failed causing excess fuel delivery? (Excess fuel = incomplete
combustion and soot)
Is the EGR valve stuck open? (Excess exhaust gas recirculation = insufficient oxygen,
incomplete combustion, and soot)
All information subject to change without notice. (Rev. 5/05)
7SE940 0505 Copyright © 2005 DETROIT DIESEL CORPORATION
MBE EGR TECHNICIAN'S GUIDE
O) for EGR engines (2004).
2
2
O) for non-EGR
2
O) for both non-EGR
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