jcb 672 User manual

SERVICE MANUAL
JCB 672 Mechanical Engine
EN - 9806/6900 - ISSUE 3 - 2016-08-22
This manual contains original instructions, verified by
the manufacturer (or their authorized representative).
Copyright 6-08-22 © JCB SERVICE
All rights reserved. No part of this publication may
be reproduced, stored in a retrieval system, or
transmitted in any form or by any other means,
electronic, mechanical, photocopying or otherwise,
without prior permission from JCB SERVICE.
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Foreword
The Operator's Manual
You and others can be killed or seriously injured
if you operate or maintain the machine without
first studying the Operator's Manual. You must
understand and follow the instructions in the
Operator's Manual. If you do not understand
anything, ask your employer or JCB dealer to
explain it.
Do not operate the machine without an Operator's
Manual, or if there is anything on the machine you
do not understand.
Treat the Operator's Manual as part of the machine.
Keep it clean and in good condition. Replace the
Operator's Manual immediately if it is lost, damaged
or becomes unreadable.
Contents
01 - Machine
06 - Body and Framework
09 - Operator Station
15 - Engine
18 - Fuel and Exhaust System
21 - Cooling System
33 - Electrical System
72 - Fasteners and Fixings
75 - Consumable Products
78 - After Sales

15 - Engine
00 - General
00 - General
15 - 3 9806/6900-3 15 - 3
00 - General
Introduction ...................................................... 15-3
Health and Safety ........................................... 15-7
Technical Data ................................................. 15-8
Component Identification ................................. 15-9
Operation ....................................................... 15-14
Fault-Finding .................................................. 15-17
Drain and Fill ................................................. 15-26
Clean ............................................................. 15-26
Check (Pressure) .......................................... 15-28
Remove and Install ....................................... 15-30
Store and Recommission .............................. 15-34
Introduction
Basic Description
The 6 cylinder mechanical engine has fuel ignited by
compression ignition (C.I.). The engine operates on
a four stroke cycle.
The engine is started by an electric starter motor. The
starter motor turns the engine via a pinion and teeth
on the engine flywheel, refer to (PIL 09-75).
When the engine runs the crankshaft drives the
camshaft via gears. The camshaft opens and closes
the inlet and exhaust valves and via push rods in time
with the four stroke cycle. The engine has 24 valves,
2 inlet and 2 exhaust valves for each cylinder.
The crankshaft also drives a mechanical fuel
injection pump via gears. The pump injects fuel via
injectors, or atomisers into each cylinder in time with
the four stroke cycle.
The pump injects fuel via injectors, or atomisers
into each cylinder in time with the four stroke cycle.
The pump is part of the mechanically actuated fuel
injection system, refer to (PIL 18-00).
Air is drawn into the engine, via the inlet manifold
and exhaust gases exit via the exhaust manifold. The
engine uses a turbocharger which pressurises the air
at the inlet manifold, refer to (PIL 18-36).
A mechanical lubrication oil pump is driven by
the crankshaft via gears. The pump pressurises
and circulates oil for engine lubrication and cooling
purposes.
A drive belt driven by the crankshaft, drives a
coolant circulation pump, alternator, radiator cooling
fan and other ancillaries such as an air conditioning
compressor.

15 - Engine
00 - General
00 - General
15 - 4 9806/6900-3 15 - 4
Figure 3.
1Flywheel 2Crankshaft
3Camshaft 4Inlet valves (12 off)
5Exhaust valves (12 off) 6Push rods (12 off)
7Turbocharger 8Lubrication oil pump

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Internal
The following identifies the main internal components
of a typical engine assembly. Some variants may
differ in detail.
As viewed on the right hand side. Refer to Figure 4.
Figure 4.
1Rocker assembly 2Valve bridge piece (12 off)
3Valve bridge piece (12 off) 4Inlet valve (12 off)
5Exhaust valve (12 off) 6Piston assembly (6 off)
7Connecting rod assembly (6 off) 8Crankshaft
9Main bearing - crankshaft (7 off) 10 Big end bearing - crankshaft/connecting rod (6
off)
11 Front crankshaft oil seal (not shown) 12 Flywheel

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00 - General
00 - General
15 - 6 9806/6900-3 15 - 6
6a Piston ring - top compression (6 off) 6b Piston ring - 2nd compression (6 off)
6c Piston ring - oil control (6 off) 6d Gudgeon pin (6 off)
6d Gudgeon pin circlip (12 off)
As viewed on the rear left side. Refer to Figure 5.
Figure 5.
1Flywheel 1a Flywheel - crankshaft fixing bolts (8 off)
2Fuel injector (atomiser) (6 off) 3Camshaft drive gear
4Lubrication oil pump 5Camshaft
6Tappet (12 off) 7Push rod (12 off)
8Flywheel hub

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Health and Safety
Hot Components
Touching hot surfaces can burn skin. The engine and
machine components will be hot after the unit has
been running. Allow the engine and components to
cool before servicing the unit.
Turning the Engine
Do not try to turn the engine by pulling the fan or fan
belt. This could cause injury or premature component
failure.
Notice: The engine and other components could
be damaged by high pressure washing systems.
Special precautions must be taken if the machine is
to be washed using a high pressure system.Make
sure that the alternator, starter motor and any other
electrical components are shielded and not directly
cleaned by the high pressure cleaning system. Do
not aim the water jet directly at bearings, oil seals or
the engine air induction system.
WARNING! To bleed the injectors you must turn the
engine. When the engine is turning, there are parts
rotating in the engine compartment.Before starting
this job make sure that you have no loose clothing
(cuffs, ties etc) which could get caught in rotating
parts.When the engine is turning, keep clear of
rotating parts.
Notice: Clean the engine before you start
engine maintenance. Obey the correct procedures.
Contamination of the fuel system will cause damage
and possible failure of the engine.
Notice: Do not exceed the correct level of engine
oil in the sump. If there is too much engine oil,
the excess must be drained to the correct level. An
excess of engine oil could cause the engine speed
to increase rapidly without control.
WARNING! The engine has exposed rotating parts.
Switch off the engine before working in the engine
compartment. Do not use the machine with the
engine cover open.
WARNING! Hot oil and engine components can burn
you. Make sure the engine is cool before doing
this job.Used engine crankcase lubricants contain
harmful contaminants. In laboratory tests it was
shown that used engine oils can cause skin cancer.
Notice: A drive belt that is loose can cause damage
to itself and/or other engine parts.
WARNING! Do not open the high pressure fuel
system with the engine running. Engine operation
causes high fuel pressure. High pressure fuel spray
can cause serious injury or death.
CAUTION! It is illegal to pollute drains, sewers
or the ground. Clean up all spilt fluids and/or
lubricants.Used fluids and/or lubricants, filters and
contaminated materials must be disposed of in
accordance with local regulations. Use authorised
waste disposal sites.

15 - Engine
00 - General
00 - General
15 - 8 9806/6900-3 15 - 8
Technical Data
Table 5. Basic Engine Data (Dieselmax 672 Mechanical Engine)
Engine EC - 6 Cylinder Mechanical, Turbocharged with
Intercooler
Emission compliance Non-emission
Rated speed 1800 rpm
Weight (Dry): 680 kg (1500 lb)(1)
Number of cylinders 6
Nominal bore size 106 mm (4.173 in)
Stroke 135 mm (5.314 in)
Cylinder arrangement In line
Combustion Cycle 4-stroke
Firing order 1-5-3-6-2-4
Displacement 7.148 litres
Compression ratio 18:1
Engine Compression see note(2)
Direction of rotation (viewed from front {crankshaft
pulley} end)
Clockwise
Valves 4 per cylinder
Valve clearances measured at the tappet end of the
rockers (measured cold):
see note(2)
- Inlet 0.28–0.34mm
- Exhaust 0.43–0.5mm
Lubricating oil pressure(3) 1.6 - 6.5 bar (23 - 91lb in2)
Combustion system Direct injection, mechanical fuel injection
High pressure fuel pump Mechanical inline
(1) Dry weight. No cooling fan drive.
(2) Compression variance between each cylinder should be no greater than 3.5 bar (50 lb in2).
(3) Dependent on engine temperature and speed.

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Component Identification
6 Cylinder Mechanical Engine
The following identifies the main components of a
typical engine assembly visible from the exterior.
Some variants may differ in detail.
Figure 6. Left hand Side
A
B
C
D
E
F
G
H
J
K
L
ALubrication oil dipstick BFuel injectors and high pressure fuel pipes
CLubrication oil filler cap DRocker cover
ETorsional vibration damper FLubrication oil sump
GBedplate housing HOil cooler housing with ports for remote oil filter

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15 - 10 9806/6900-3 15 - 10
JFuel injection pump KHigh pressure fuel pipes
LLifting eye head
Figure 7. Right hand side
E
L
p
D
C
J
M
A
B
K
H
G
F
N
ATiming gear case BFlywheel housing
CBedplate housing DLubrication oil sump
ETurbocharger FExhaust manifold
GAlternator HCoolant pump housing (crankcase)
JCoolant inlet/radiator hose connector KHeavy duty PTO (Power Take-Off) (blanking
cover if no device is installed)
LStarter motor assembly MTurbocharger oil drain line
NTurbocharger oil feed line POil drain plug (sump)

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15 - 11 9806/6900-3 15 - 11
Figure 8. Crankshaft pulley (front) end
L
K
B
J
H
F
A
C
G
D
E
ARocker cover BCylinder head
CCrankcase DBedplate
ELubrication oil sump FTorsional vibration damper
GFEAD (Front End Accessory Drive) tensioner HStarter motor
JAlternator and drive pulley assembly KTwin thermostat
LTurbocharger

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Figure 9. Flywheel (rear) end
G
F
D
A
B
E
C
ARocker cover BCylinder head
CFlywheel DFuel injection pump gear access cover
ETiming case FInlet manifold
GTurbocharger

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15 - 13 9806/6900-3 15 - 13
Figure 10. 6 Cylinder mechanical engine (ISO) view
M
A
B
C
D
E
F
G
H
J
K
L
AInlet manifold BOil cooler remote
CFEAD belt tensioner DTorsional vibration damper
ECoolant pump drive pulley FLubrication oil sump
GOil drain plug (sump) HStarter motor assembly
JWater inlet connector KAlternator and drive pulley assembly
LTurbocharger MFuel injector cover
JCoolant inlet connector

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Operation
The Four Stroke Cycle
This section describes the cycle sequence, for the 6
cylinders of the diesel engine.
The stages in the four stroke cycle for each cylinder
are as follows:
Table 6. The Four Stroke Cycle
Stage number Piston operation Valve operation
1 The piston is at the top of its Com-
pression stroke and is about to
start its Power stroke.
Inlet and exhaust valves closed.
2 The piston is at the bottom of its
Power stroke and is about to start
its Exhaust stroke.
Inlet valves closed, exhaust valves
about to open.
3 The piston is at the bottom of its In-
duction stroke and is about to start
its Compression stroke.
Exhaust valves closed, inlet valves
about to close.
4 The piston is at the top of its Ex-
haust stroke and is about to start
its Induction stroke.
Valve operation exhaust valves
about to close, inlet valves about to
open.
Firing order
A cylinder is said to be firing, when the fuel/air mixture
ignites and the piston is about to start its power
stroke.
Four Stroke Cycle
Induction
As the piston travels down the cylinder, it draws
filtered air at atmospheric pressure and ambient
temperature through an air filter and inlet valves into
the cylinder.
Compression
When the piston reaches the bottom of its stroke the
inlet valves close. The piston then starts to rise up the
cylinder compressing the air trapped in the cylinder.
This causes the temperature and pressure of the air
to rise. Fuel is injected into the cylinder when the
piston is near to top dead centre.
Power
The piston continues to rise after the start of fuel
injection causing a further increase in pressure and
temperature.
The temperature rises to a point at which the fuel/air
mixture ignites. A cylinder is said to be firing, when
the fuel/air mixture ignites.
This combustion causes a very rapid rise in
both temperature and pressure. The high pressure
generated propels the piston downward turning the
crankshaft and producing energy.
Exhaust
Once the piston has reached the bottom of its travel,
the exhaust valves open and momentum stored
in the flywheel forces the piston up the cylinder
expelling the exhaust gases.
In a running engine these four phases are
continuously repeated. Each stroke is half a
revolution of the crankshaft, thus, in one cycle of a
four stroke engine, the crankshaft revolves twice.

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Figure 11.
3
2
4
1
B
C
746030
1Induction 2Compression stroke
3Power stroke 4Exhaust stroke
ACamshaft BCamshaft lobe - Inlet valve operation
CCamshaft lobe - Exhaust valve operation BDC Bottom dead centre
TDC TDC (Top Dead Centre)

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