TROUBLESHOOTING
Page 93
There are some operating conditions where the
engine will not achieve no-load governed RPM by
design. These conditions are:
앫 Customer data
앫 High vehicle acceleration at light load
EXCESSIVE BLACK OR GRAY SMOKE
Black smoke is primarily a mechanical problem.
The electronic V-MAC III system does not
contribute to black smoke. Instead, the system
derates engine power by reducing the amount of
fuel supplied, for example, in response to a
malfunctioning sensor.
Routine EGR service or wiring inspection IS NOT
required in response to a black smoke condition.
Possible Cause Correction
1. Intercooler core leakage. 1. Pressure-test intercooler. If test results are unsatisfactory, remove,
repair or replace intercooler as needed.
2. Intercooler core fin obstructions. 2. Clean intercooler fins.
3. Insufficient air for combustion. 3. Check air cleaner for restrictions. Check inlet manifold pressure,
and inspect the turbocharger for proper operation. Repair or
replace as required.
4. Excessive exhaust back-pressure. 4. Check for faulty exhaust piping or restrictions in the muffler. Repair
or replace as required.
5. Improper grade of fuel. 5. Drain fuel from tank(s). Replace fuel filters and fill tank(s) with
MACK-specified diesel fuel.
6. Defective fuel injection nozzle or unit pump. 6. Isolate defective nozzle and replace. Refer to item 8 under
ENGINE MISFIRES — NO CODE(S) chart.
7. Improper engine valve adjustment. 7. Reset valve adjustment.
8. Malfunctioning exhaust/intake valve. 8. Repair cylinder head/valve train.
9. EGR valve stuck open. 9. Inspect EGR valve components for carbon fouled, soot buildup or
corrosion. Replace the valve to correct. To test: With the engine
running and EGR gases flowing, unplug the EGR valve. The valve
should close. If not, replace the valve.
10. EGR MFS sensor malfunctioning. 10. Replace EGR MASS Flow System.
5-111.bk Page 93 Monday, July 10, 2006 2:26 PM
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