Mack ASET AC, Service Manual

Page: 111 / 536

Page 98
TROUBLESHOOTING
LOW COMPRESSION
FUEL IN LUBE OIL
EGR SYSTEM MALFUNCTION (WITH COOLER AND VTG TURBOCHARGER)
Possible Cause Correction
1. Improper valve lash adjustment. 1. Adjust valve lash to specified clearance.
2. Blown head gasket. 2. Replace head gasket.
3. Broken or weak valve springs. 3. Check and replace defective parts as required.
4. Valves not seating properly. 4. Remove, recondition and reinstall heads.
5. Piston rings stuck, worn, broken or improperly
seated.
5. Determine and correct root cause and repair engine as required.
6. Camshaft or valve lifters worn. 6. Replace camshaft and/or valve lifters and perform any other
necessary repairs as required.
Possible Cause Correction
1. Excessive idling, especially in cold weather. 1. Minimize idling time and use all recommended cold weather
accessories.
2. Injector nozzle malfunctioning. 2. Remove and pop-test nozzles. Clean or replace nozzles as
required.
3. Unit pump O-ring leaking. 3. Replace O-rings. Inspect cylinder block bores for wear or damage.
4. Front fuel gallery plug. 4. Check for leakage of plug through supply pump mounting bore.
Possible Cause Correction
1. Excessive idling, especially in cold weather
causing carbon buildup in the EGR cooler that
blocks the flow of exhaust gas.
1. Minimize idling time and use all recommended cold weather
accessories.
2. High EGR temperature out of the cooler indicates
a failed cooler or coolant block.
2. Replace EGR cooler or correct coolant block.
3. EGR valve not working or sticking. 3. Check for correct oil supply to valve. Check for oil coking or
corrosion at the actuator bushing area. Also check for wire harness
failure including connectors.
4. EGR valve housing cracked. 4. Inspect EGR housing and replace as necessary.
5. EGR valve not functioning properly due to low oil
pressure.
5. Determine reason for low oil pressure. Refer to LOW ENGINE OIL
PRESSURE chart.
6. Turbocharger position does not follow the
command.
6. This could be caused by mechanical or electrical problems with the
VTG. Check codes related to VTG and check for mechanical
problems at the turbo. Replace as necessary.
Note: Verify that chassis air supplied to the VTG position controller
(Rexroth
®
valve) is at least 95 psi.
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