Detroit Diesel MBE 900 Technician Manual page 14

INTRODUCTION
Is the Intake Manifold Pressure (IMP) Sensor/Turbocharger Boost Sensor (TBS) working
correctly?
The basic questions to ask for Blue Exhaust Smoke are:
NOTE:
Blue Smoke is partially burned lubrication oil that ends up as a raw vaporized oil in the
exhaust soot from partially oxidized (burned) fuel at high temperatures.
Is the comparative cylinder compression test result correct/within specifications? (Low
compression = incomplete/poor combustion)
Is the oil level above the maximum level? (Excess oil = poor combustion and raw
vaporized oil in the exhaust)
Does the oil quality meet the recommended specification? (Poor quality oil = piston
ring wear and poor combustion)
Is the turbocharger leaking oil into the exhaust? (Oil in exhaust = poor combustion)
Are the valve stem seals functioning? (Oil leaking past seal = poor combustion)
The basic questions to ask for White Exhaust Smoke are:
NOTE:
White Smoke is usually partially burned fuel that ends up as raw vaporized fuel in the
exhaust. White Smoke can also be the result of a coolant leak that ends up as steam
in the exhaust.
Is the fuel quality within DDC specification? (Cetane No. minimum: 45, Cetane Index,
minimum: 40)
Is the air preheater installed and functioning properly? (Cold air = raw vaporized fuel
in the exhaust)
Are there air bubbles in the coolant? (Suggests a head gasket failure = vaporized water in
exhaust)
Are there air bubbles in the fuel? (Suggests a fuel line/pump leak = late fuel injection =
raw vaporized fuel in exhaust)
Are the valve clearances correct? (Incorrect valve timing = incorrect combustion timing)
Is the charge air cooler cracked? (Reduced air flow = incomplete combustion and soot)
NOTE:
Refer to Service Information Letter 05 TS-01 for service information on cracked charge
air coolers. See Figure C-16 and Figure C-17.
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 raw fuel in exhaust)
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All information subject to change without notice. (Rev. 5/05)
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