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ENGINE
18
PRELIMINARY INSPECTION OF ENGINE
B
efore
proceeding
to
carry
out
actual
reconditioning of engine it is desirable to have a
preliminary inspection of engine to ascertain whether
an engine recondition is necessary and to what extent.
M
ost common reasons for which engine is
reconditioned are :
1. Loss of power
2. Excessive engine oil consumption.
3. Excessive low engine oil pressure
4. Mechanical failures
To know exact reason and general condition of engine,
proceed as follows :
1. LOSS OF POWER
Loss of engine power may be due to :
a.
Clogged air cleaner / loss of charge air
pressure / choked exhaust silencer
b.
Clutch slippage
c.
Brake binding
d.
Defective fuel injection system
e.
Loss of engine compression
a. CLOGGED AIR CLEANER / LOSS OF CHARGE AIR
PRESSURE / CHOCKED EXHAUST SILENCER
L
oss of power indicates lack of air or low air charging
pressure to engine cylinders. Loss of charge pressure
can be due to leakage of charge air from outlet of
turbocharger, worn out vanes of turbocharger,
compressor & leakage in the inlet manifold etc.
C
lean air filter. Check all joints for air leakage. If power
loss with black smoke is still felt, check exhaust silencer
and catalytic converter for choking. Clean and replace
silencer/catalytic converter if necessary.
b. CLUTCH SLIPPAGE
Clutch slipping can be confirmed by any of the
following two methods :
D
rive vehicle in 1st and 2nd gear at maximum speed
corresponding to that gear. With accelerator pedal
fully pressed, apply brake gradually with left foot. If
the engine stalls it means that clutch does not slip.
D
rive loaded vehicle in 3rd gear on level ground and
let the speed drop down to approximately 15 kmph.
Now press accelerator pedal fully. With slipping clutch
the vehicle speed will not pick up and also clutch
burning smell will be noticed. If this does not occur
and vehicle picks up speed, it indicates that clutch
does not slip.
c. BRAKE BINDING
During driving apply brakes number of times and then
shift gear to neutral position check brake drums/brake
discs for overheating and if necessary jack up axles
and check wheels for free rotation.
Check hand brake position (Released or applied)
d. FUEL INJECTION SYSTEM
C
heck condition of fuel filters for clogging, low pressure
fuel lines for any leakages. If check engine lamp comes
''ON'' follow the diagnostics procedure.
e. CHECKING ENGINE COMPRESSION
PRESSURE
-
I
f loss of power is not on account of defective fuel
system, lack of air, choked exhaust system, clutch
slipping and brake binding, then
C
heck engine compression as follows.
- Warm up engine preferably by road drive to get a
temperature of about 85
o
to 95
o
C.
R
emove all injectors. Flame guard washers should
be replaced while refitting the injectors.
-
F
it adaptor in place of one injector.
-
C
onnect compression tester to adaptor and tighten
vent knob.
-
C
rank engine with starter motor by 200-350 rpm
approx. Pressure gauge needle will start rising.
Continue cranking till gauge needle stops rising
any further. Note down reading. Loosen vent knob
to make sure the tester needle returns to zero.
Repeat this operation for remaining cylinders.
-
M
inimum compression pressure in each cylinder
should be 16 bar. Variation in compression
pressure between cylinders should not be more
than 1.5 bar.
-
L
ow compression pressure may be due to leakage
past valves / piston rings /blown cylinder head
gasket. To ascertain the point of leakage, spray
small quantity of clean engine oil in to cylinder
showing low pressure. If it improves, wear in
piston rings / cylinder bore is indicated. If it does
not, leakagepast thevalves is indicated. If compression
pressure of adjacent cylinder is also on lower side