AJ16 Engine Service Manual
FAULT DIAGNOSIS
3.1 Introduction
The following diagnostic procedures are provided to assist properly qualified persons to identify and rectify the faults
relating to the engine which are most likely to encountered. Reference is made to the Electrical Diagnostic Manual
(EDM), which should be consulted where necessary. Faults related to the cooling system are dealt with in Section 4.1
and to the fuel system in Section 5.1 in the appropriate Vehicle Service Manual (VSM).
3.2 Diagnostic Procedures
(fails to rotate)
I Engine rotates but 0 I will not fire
I
i
/Overheating
Overheating at tick-
Too cold
Loss of coolant Possible
Cause
Battery leads loose or ter
- minals corroded
Battery discharged
Starter motor inoperative
Starter motor speed too
low
Faulty ignition system
Fuel system defect
Oil requires changing
Worn crankshaft journals
Excessive crankshaft
end- float
Worn main bearing shells
Worn oil pump Oil pressure relief valve stick
- ing open
Oil pressure relief valve
spring too weak
Insufficient oil in oil pan
Engine overheating
Faulty gauge or sensor
Incorrect grade oil (viscosity
too low)
Water in oil Check
Check the condition of the
leads and terminals
Check condition of battery
with hydrometer
If the lights dim when ignition
switch is operated, the starter
may be jammed in starter
ring.
Check for loose and dirty con
- nections to the starter motor
Check battery leads and ter
- minals
Check state of battery charge
Refer to EDM
Remove the spark plugs
Check oil level and color
Listen for rumble or knock
Fit dial gauge and measure
Listen for rumble
Remove oil pump and check
the clearances
Remove valve and check for
sticking
Remove spring and check
spring rates
Check oil level
Refer to EDM
Check oil viscosity
Checkoil level and check if oil
is a milky white color
Check for leaking head gasket Remedy
Clean and tighten as necess
-
ary
Charge or renew battery as
necessary
Remove starter motor, free
off pinion and refit
Clean and tighten connec
- tions
Clean and tighten terminals
Charge or renew battery
as necessary
Rectify as required
Clean and re
-gap the spark
plugs, renew if worn out
Refer to Fuel System fault
finding in Section
5.1, VSM
Refer to Section
4.1, VSM
Refer to Section
4.1, VSM
Refer to Section
4.1, VSM
Refer to Section
4.1, VSM
Change oil and filter
Renew crankshaft
Renew thrust washers
Check crankshaft journals for
wear and renew shells
Renew oil pump
Renew valve
Renew spring
lop-up as required
Refer to Overheating fault
finding in Section
4.1, VSM
Rectify as required
Renew oil and filter
Renew oil and filter
Renew head gasket
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AJ16 Engine Service Manual
Symptom Possible Cause ~~
nsufficient
oil pres- ure (continued)
lil pressure too high
3urning oil
.osing oil (leaking)
Excessive noise
'rom valve gear Cracked
oil pump housing
Blocked oil pick
-up pipe
strainer
Oil pump pipe
'0' rings
Main oil gallery seals leaking
or gallery blocked
Relief valve stuck shut
Wrong pressure relief valve
Incorrect grade engine oil
(viscosity too high)
Gauge or sensor fault
Engine temperature too low
Worn cylinder bores
Worn valve guides
Worn intake valve seals
Worn piston rings
Cylinder head gasket leaking
Incorrect grade of engine oil
Worn front oil seal
Worn rear oil seal
Leaking gaskets
Cylinder block cracked
Excessive valve clearance
Broken valve
spring(s)
Broken valve guide
Broken valve seat insert
Lack of lubrication
Valve clash
Worn
camshaft(s)
Worn camshaft drive chains i tensioners
Check
Remove oil pan and visually
check
Remove oil pan and visually
check
Removeoil
panand pipesand check Eliminate other possible
causes
Remove valve and check for
sticking
Remove spring and check the
rate
Check oil viscosity
Refer to EDM
Check wear with
a compara- tor
Insert valve in guide and
check side movement
Remove seals and check for
splits or wear
Measure rings in bore
Check for blue smoke from
exhaust
Check oil viscosity
Wipe clean, run engine and
visually check
Wipe bell housing clean, run
engine and visually inspect
for cleanliness
Visual check
Visual check
Check valve clearances
Remove valves and check
springs
Remove valves and check
guides
Remove valves and check in
- serts
Check oil pressure gauge re
- ading
Check valve timing
Check valve clearances and
for lack
of lubrication
Remove front timing cover
and check for wear
Remedy
Renew the pump
Remove oil pick
-up pipe and
clean strainer
Fit new '0' rings
Fit new '0 rings or clear oil
gallery
Clean or renew the valve
Renew spring
Renew oil and filter
Rectify as required
RefertoToo Cold fault finding
in Section 4.1, VSM
Rebore cylinders as necess
-
ary
Renew valve guides as
necessary
Renew in sets
Renew rings in sets and re
- bore as necessary
Renew head gasket
Renew oil and filter
Renew seal
Renew seal
Renew gasket Renew cylinder block
Adjust valve clearances
Renew as necessary
Renew as necessary
Renew as necessary
Refer to Insufficient Oil Pres
- sure fault finding
Adjust valve timing
Adjust valve clearances.
Refer to Insufficient Oil Pres
- sure fault finding
Renew as
necessaw
0
0
0 ~~~
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