Engine Diagnosis; Service Diagnosis - Mechanical - Dodge D150 1990 Service Manual

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ENGINE 9 - 7
ENGINE DIAGNOSIS
INDEX
Page
Checking Engine Oil Pressure 9
General Information
7
Inspection For Engine Oil Leaks
9
GENERAL INFORMATION
Engine diagnosis is helpful i n d e t e r m i n i n g t h e
causes of malfunctions not detected and remedied by
routine tune-ups.
These malfunctions may be classified as either me-
chanical (e.g., a strange noise), or performance (e.g.,
engine idles r o u g h and stalls).
SERVICE DIAGNOSIS - MECHANICAL
CONDITION
POSSIBLE CAUSES CORRECTION
NOISY VALVES • High and low oil level in crankcase
• Thin or diluted oil
• Low oil pressure
• Dirt in lash adjusters
• Worn rocker arms
• Worn lash adjusters
• Worn valve guides
• Excessive runout of valve seats or valve
faces
• Check for correct oil level. Refer to Group
0, Lubrication and Maintenance.
• Change oil. Refer to Group 0, Lubrication
and Maintenance.
• Check engine oil level.
• Clean hydraulic lash adjusters.
• Inspect oil supply to rocker arms.
• Install new hydraulic lash adjusters.
• Ream and install new valves with oversize
stems.
• Grind valve seats and valves.
CONNECTING ROD NOISE • Insufficient oil supply
• Low oil pressure
• Thin or diluted oil
• Excessive bearing clearance
• Connecting rod journal out-of-round
• Misaligned connecting rods
• Check engine oil level. Refer to Group 0,
Lubrication and Maintenance.
• Check engine oil level. Inspect oil pump
relief valve and spring.
• Change oil to correct viscosity.
• Measure bearings for correct clearance.
• Replace crankshaft or grind journals.
• Replace bent connecting rods.
MAIN BEARING NOISE
• Insufficient oil supply
• Low oil pressure
• Thin or diluted oil
• Excessive bearing clearance
• Excessive end play
• Crankshaft journal out-of-round worn
• Loose flywheel or torque converter
• Check engine oil level. Refer to Group 0,
Lubrication and Maintenance.
• Check engine oil level. Inspect oil pump
relief valve and spring.
• Change oil to correct viscosity.
• Measure bearings for correct clearance.
• Check No. 3 main bearing for wear on
flanges.
• Replace crankshaft or grind journals.
• Tighten to correct torque.
OIL PRESSURE DROP
• Low oil level
• Low oil pressure
• Clogged oil filter
• Worn parts in oil pump
• Thin or diluted oil
• Excessive bearing clearance
• Oil pump relief valve stuck
• Oil pump suction tube loose, bent or
cracked
• Check engine oil level.
• Check sending unit.
• Install new oil filter
• Replace worn parts or pump.
• Change oil to correct viscosity.
• Measure bearings for correct clearance.
• Remove valve and inspect, clean and
install.
• Remove oil pan and install new tube, if
necessary.
OIL LEAKS • Misaligned or deteriorated gaskets
• Loose fastner, broken or porous metal part
• Replace the gasket.
• Tighten, repair or replace the part.
J9009-122
Page
Service Diagnosis - Mechanical
7
Service Diagnosis - Performance 8
Refer t o t h e Service Diagnosis—Mechanical chart
and t h e Service Diagnosis—Performance ch ar t for
possible causes a n d corrections o f malfunctions. Refer
to Group 14, F u e l System for the fuel system diagno-
sis.