Doosan G420F User manual

Service Manual
G420FE LP/Dual Fuel Engine
G420F LP/Gasoline Dual Fuel Engine
G15S-5, G18S-5, G20SC-5
GC15S-5, GC18S-5, GC20SC-5
G20E-5, G25E-5, G30E-5
GC20E-5, GC25E-5, GC30E-5, GC33E-5
SB4241E00
Apr. 2007

1
Important Safety Information
Most accidents involving product operation, maintenance and repair are caused by failure to observe basic
safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations
before an accident occurs. A person must be alert to potential hazards. This person should also have the
necessary training, skills and tools to perform these functions properly.
Read and understand all safety precautions and warnings before operating or performing lubrication,
maintenance and repair on this product.
Basic safety precautions are listed in the “Safety” section of the Service or Technical Manual. Additional safety
precautions are listed in the “Safety”section of the owner/operation/maintenance publication.
Specific safety warnings for all these publications are provided in the description of operations where hazards
exist. WARNING labels have also been put on the product to provide instructions and to identify specific
hazards. If these hazard warnings are not heeded, bodily injury or death could occur to you or other persons.
Warnings in this publication and on the product labels are identified by the following symbol.
WARNING
Improper operation, lubrication, maintenance or repair of this product can be dangerous and could
result in injury or death.
Do not operate or perform any lubrication, maintenance or repair on this product, until you have read
and understood the operation, lubrication, maintenance and repair information.
Operations that may cause product damage are identified by NOTICE labels on the product and in this
publication.
DOOSAN cannot anticipate every possible circumstance that might involve a potential hazard. The warnings
in this publication and on the product are therefore not all inclusive. If a tool, procedure, work method or
operating technique not specifically recommended by DOOSAN is used, you must satisfy yourself that it is
safe for you and others. You should also ensure that the product will not be damaged or made unsafe by the
operation, lubrication, maintenance or repair procedures you choose.
The information, specifications, and illustrations in this publication are on the basis of information available at the
time it was written. The specifications, torques, pressures, measurements, adjustments, illustrations, and other
items can change at any time. These changes can affect the service given to the product. Obtain the complete and
most current information before starting any job. DOOSAN dealers have the most current information available.

G420F(FE) Service Manual Index3
Index
Chapter 1. GENERAL INFORMATION
Precautions before Service.................................7
Tightening Torque .............................................10
Recommended Lubricants and Capacities.......11
Engine Model and Engine Serial Number.........12
General Specification ........................................13
Engine Power and Torque.................................15
Chapter 2. RECOMMENDED
MAINTENANCE
General Maintenance.........................................16
Test Fuel System for Leaks...........................16
Inspect Engine for Fluid Leaks ......................16
Inspect Vacuum Lines and Fittings................16
Inspect Electrical System..............................16
Inspect Foot Pedal Operation........................16
Engine Oil Classification................................17
Checking Engine Oil Level............................18
Replacing Engine Oil and Filter.....................18
Checking Compressed Pressure...................19
Adjusting Timing Belt Tension.......................20
Cooling System Maintenance............................21
Coolant Recommendation.............................21
Check Coolant Level.....................................21
Inspect Coolant Hoses..................................21
Checking coolant leaks.................................22
Specific gravity test.......................................22
Relation between Coolant concentration and
Specific Gravity.............................................22
Checking and Adjusting Drive Belt ................23
Adjusting.......................................................24
Checking Belt for Damage ............................24
Ignition System Maintenance............................25
Inspect Battery System.................................25
Inspect Ignition System................................. 25
Inspection of Ignition Timing......................... 25
Inspection of Spark Plug............................... 26
Fuel System Maintenance................................. 28
Replace LP Fuel Filter Element..................... 28
Testing Fuel Lock-off Operation.................... 29
Pressure Regulator/Converter Inspection...... 29
Inspect Air/Fuel Valve Mixer Assembly ......... 30
Inspect for Intake Leaks................................ 30
Inspect Throttle Assembly............................. 30
Checking the TMAP Sensor.......................... 30
Exhaust System Maintenance........................... 30
Inspect Engine for Exhaust Leaks................. 30
Maintenance Schedule...................................... 31
Chapter 3. ENGINE MECHANICAL
SYSTEM
General Information........................................... 33
Engine Outline.............................................. 33
Specifications............................................... 34
Specifications............................................... 35
Torque Specification..................................... 38
Special Tools................................................ 39
Troubleshooting............................................ 41
Timing Belt System........................................... 42
Components................................................. 42
Removal....................................................... 43
Inspection..................................................... 44
Assembly...................................................... 46
PCV Valve.......................................................... 48
Outline and Operation Principle .................... 48
Service Procedure........................................ 49
Intake and Exhaust System............................... 50
Intake Manifold............................................. 50
Exhaust Manifold.......................................... 52
Cooling System ................................................. 54
General Description...................................... 54
Testing and Adjusting................................... 55

G420F(FE) Service Manual Index4
Cooling System Recommendation ................58
Coolant Pipe and Hose .................................60
Water Pump..................................................61
Thermostat ...................................................63
Cylinder Head Assembly...................................65
Lubrication System............................................74
General Description ......................................74
Testing and Adjusting....................................75
Oil Pressure Switch.......................................77
Front Case and Oil Pump..............................78
CAM Shaft, HLA, Timing Chain .........................83
Components .................................................83
Removal.......................................................84
Inspection.....................................................85
Crankshaft..........................................................90
Flywheel and Housing.......................................94
Piston and Connection Rod ..............................95
Cylinder Block..................................................110
Chapter 4. ENGINE ELECTRICAL
SYSTEM
Specifications.................................................. 118
Ignition System................................................119
Coil-On-Plug Ignition System......................119
COP Components.......................................119
Inspection of Ignition Timing........................122
Inspection of Ignition Coil Drivers (Power TR)
...................................................................122
Inspection of Ignition Coil............................123
Inspection of Spark Plug.............................124
Charging System............................................. 126
General Description ....................................126
Troubleshooting..........................................128
Disassembly and Installation.......................134
STARTING SYSTEM.........................................139
General Description ....................................139
Diagnosis Procedure...................................140
Start Relay Tests........................................142
Troubleshooting...........................................143
Starter.........................................................144
Chapter 5. ENGINE MANAGEMENT
SYSTEM (EMS)
General Information..........................................150
Specifications..............................................150
Service Standard.........................................155
Component Location....................................156
G420FE EMS (Engine Management System)
Overview...........................................................160
General Description.....................................160
LPG Fuel System Operation........................163
MPI Gasoline System Operation..................170
Electronic Throttle System...........................171
Ignition System............................................172
Exhaust System...........................................173
SECM..........................................................175
SECM Wiring Diagrams for G420FE............178
G420F EMS (Engine Management System)
Overview...........................................................180
General Description.....................................180
LPG Fuel System Operation........................183
MPI Gasoline System Operation..................187
Electronic Throttle System...........................187
Ignition System............................................187
Exhaust System...........................................187
SECM..........................................................187
SECM Wiring Diagrams for G420F ..............188
EMS Inspection and Repair..............................189
Engine Control Module (SECM)...................189
Camshaft Position Sensor ...........................191
Crank Shaft Position Sensor........................192
MAP (Manifold Absolute Pressure) Sensor ..193
IAT (Intake Air Temperature) .......................194

G420F(FE) Service Manual Index5
Sensor........................................................ 194
Oxygen Sensor (Pre-Catalyst)..................... 195
Oxygen Sensor (Post-Catalyst)................... 196
ECT (Engine Coolant Temperature) Sensor 197
LP Fuel Temperature Sensor...................... 199
Angle Sensor-Accelerator ........................... 200
Transmission Oil Temperature Switch......... 201
Ground Speed Limit Switch (optional) ......... 202
Electronic Throttle Body.............................. 203
Chapter 6. LPG FUEL DELIVERY
SYSTEM
G420FE LP System Inspection and Repair.....204
Removal and Installation............................. 204
Hose Connections.........................205
Removal and Installation of...........206
N-2007 LP Regulator ....................206
Removal and Installation of CA100
Mixer for G420FE..........................207
Tests and Adjustments................................ 209
N-2007 Regulator Service Testing. 210
AVV (Air Valve Vacuum) Testing... 211
AVV (Air Valve Vacuum) Testing... 212
Connection of the MI-07 Service Tool
.....................................................212
Idle Mixture Adjustment................. 213
Parts Description......................................... 216
CA100 Mixer for G420FE Engine .. 216
N-2007 Regulator for G420FE Engine
.....................................................218
G420F LPG System Inspection and Repair.....220
Removal and Installation............................. 220
G420F Fuel System Connections.. 221
Removal and Installation of N-2001 LP
Regulator/Converter...................... 222
Removal and Installation of CA100
Mixer for G420F............................223
Tests and Adjustments................................ 225
N-2001 Regulator Service Testing .225
AVV (Air Valve Vacuum) Testing....227
Connection of the MI-07 Service Tool
......................................................227
Idle Mixture Adjustment .................228
Parts Description.........................................230
CA100 Mixer for G420F Engine .....230
N-2001 Regulator for G420F Engine
......................................................234
Chapter 7. MPI GASOLINE FUEL
DELIVERY SYSTEM
Specification.....................................................239
Special Tools....................................................239
Components Location......................................240
Fuel Pressure Test ...........................................241
Injector..............................................................243
Injector Inspection............................................245
Fuel Pump.........................................................247
Chapter 8. BASIC TROUBLESHOOTING
Preliminary Checks ..........................................248
Before Starting ............................................248
Visual/Physical check..................................248
Basic Troubleshooting Guide..........................249
Customer Problem Analysis Sheet...............249
Basic Inspection Procedure .........................250
Connector Inspection Procedure..................251
Symptom Troubleshooting Guide Chart .......255
Basic Troubleshooting.....................................261
Intermittents.................................................261
Surges and/or Stumbles ..............................262
Engine Cranking but Will Not Start / Difficult to
Start............................................................263
Lack of Power, Slow to Respond / Poor High
Speed Performance / Hesitation During
Acceleration.................................................265

G420F(FE) Service Manual Index6
Detonation / Spark Knock............................ 267
Backfire ...................................................... 268
Dieseling, Run-on ....................................... 268
Rough, Unstable, Incorrect Idle, or Stalling.. 269
Cuts Out, Misses......................................... 271
Poor Fuel Economy / Excessive Fuel
Consumption LPG Exhaust Smell ............... 272
High Idle Speed .......................................... 273
Excessive Exhaust Emissions or Odors....... 274
Diagnostic Aids for Rich / Lean Operation... 275
Chart T-1 Restricted Exhaust System Check276
Chapter 9. ADVANCED DIAGNOSTICS
Reading Diagnostic Fault Codes..................... 277
Displaying Fault Codes (DFC) from SECM
Memory............................................................. 277
Clearing Fault (DFC) Codes............................. 277
Fault Action Descriptions................................ 278
Fault List Definitions........................................ 278
Table 1. Fault List Definitions......................279
Table 2. Diagnostic Fault Codes (Flash Codes)
................................................................... 289
Appendix
Service Tool Software (MotoView).................. 307
Service Tool Connection to SECM .............. 308
Service Tool Display ................................... 309
SECM field update with Service Tool...........313
SECM field update with Service Tool...........314
Ground Speed Limits (Option)........................ 318
LPG And LPG Fuel Tanks................................ 320
Regulatory Compliance................................... 324
Special Conditions for Safe Use ..................... 324
Abbreviations................................................... 325

G420F(FE) Service Manual Chapter 1. General Information7
Chapter 1. GENERAL INFORMATION
Precautions before Service
Removal and Disassembly
For prevention of wrong installation or reassembly
and for ease of operation, put mating marks to the
parts where no function is adversely affected.
Special Tool
Be sure to use Special Tools when their use is
specified for the operation.
Use of substitute tools will result in malfunction of
the part or damage it.
Tightening Torque
Tighten the part properly to specified torque.
Sealant
Use specified brand of sealant.
Use of sealant other than specified sealant may
cause water or oil leaks.

G420F(FE) Service Manual Chapter 1. General Information8
Replacement Part
When oil seal, O-ring, packing and gasket have
been removed, be sure to replace them with new
parts.
However, rocker cover gasket may be reused if it is
not damaged.
Rubber Parts
Do not stain timing belt and V-belt with oil or water.
Therefore, do not clean the pulley and sprocket with
detergent.
Oil and Grease
Before reassembly, apply specified oil to the rotating
and sliding parts.
Genuine Part
When the part is to be replaced, be sure to use
genuine part.
For selection of appropriate parts, refer to the Parts
Catalog.
Electrical System
1. Be sure to disconnect the battery cable from the
negative(-) terminal of the battery.
2. Never pull on the wires when disconnecting
connectors.
3. Locking connectors will click when the connector
is secure.
4. Handle sensors and relays carefully. Be careful
not to drop them or hit them against other parts.

G420F(FE) Service Manual Chapter 1. General Information9
Precautions for catalytic Converter
CAUTION
If a large amount of unburned gasoline flows
into the converter, it may overheat and create a
fire hazard. To prevent this, observe the
following precautions and explain them to your
customer.
1. Use only unleaded gasoline.
2. Do net run the engine while the truck is at rest for
a long time. Avoid running the engine at fast idle
for more than 5 minutes and at idle speed for
more than 10 minutes.
3. Avoid spark-jump tests. Do spark-jumps only
when absolutely necessary. Perform this test as
rapidly as possible and, while testing, never race
the engine.
4. Do not measure engine compression for an
extended time. Engine compression tests must be
made as rapidly as possible
5. Do not run the engine when the fuel tank is nearly
empty. This may cause the engine to misfire and
create and extra load on the converter.
6. Avoid coasting with the ignition turned off and
during prolonged braking
7. Do not dispose of a used catalytic converter
together with parts contaminated with gasoline or
oil.

G420F(FE) Service Manual Chapter 1. General Information10
Tightening Torque
Tightening Torque Table of Standard Parts
Torque (kg·m)
Bolt nominal
diameter(mm) Pitch(mm) Head mark 4 Head mark 7
M5 0.8 0.3 ~ 0.4 0.5 ~ 0.6
M6 1.0 0.5 ~ 0.6 0.9 ~ 1.1
M8 1.25 1.2 ~ 1.5 2.0 ~ 2.5
M10 1.25 2.5 ~ 3.0 4.0 ~ 5.0
M12 1.25 3.5 ~ 4.5 6 ~ 8
M14 1.2 7.5 ~ 8.5 12 ~ 14
M16 1.5 11 ~ 13 18 ~ 21
M18 1.5 16 ~ 18 26 ~ 30
M20 1.5 22 ~ 25 36 ~ 42
M22 1.5 29 ~ 33 48 ~ 55
M24 1.5 37 ~ 42 61 ~ 70
M5 0.8 0.3 ~ 0.4 0.5 ~ 0.6
M6 1.0 0.5 ~ 0.6 0.9 ~ 1.1
M8 1.25 1.2 ~ 1.5 2.0 ~ 2.5
M10 1.25 2.5 ~ 3.0 4.0 ~ 5.0
NOTE: The torques shown in the table are standard
vales under the following conditions.
1. Nuts and bolt are made of steel bar and
galvanized.
2. Galvanized plain steel washers are inserted.
3. All nuts, bolts, plain washers are dry.
NOTE: The torques shown in the table are not
applicable,
1. When spring washers, toothed washers and the
like are inserted.
2. If plastic parts are fastened.
3. If oil is applied to threads and surfaces.
NOTE: If you reduce the torques in the table to the
percentage indicated below under the following
conditions, it will be the standard value.
1. If spring washers are used : 85%
2. If threads and bearing surfaces are stained with
oil: 85%

G420F(FE) Service Manual Chapter 1. General Information11
Recommended Lubricants and Capacities
Recommended Lubricants
Lubricant Specification Remarks
Engine Oil API Classification SJ or above SAE 10W30 or SAE 5W30
Coolant (Antifreeze) Automotive antifreeze suitable for gasoline engines
having aluminum alloy parts
Concentration level 50%(normal)
Concentration level 40%(tropical)
Lubricant Capacities
Description G(C)18S-5, G(C)20SC-5 G(C)20/25/30E-5
Oil Pan 3.7 3.7
Oil Filter 0.3 0.3
Engine Oil (liters)
Total 4.0 4.0
Engine 3.0 3.0
Radiator & Hoses 5.5 5.5
Coolant (liters)
Total 8.5 8.5

G420F(FE) Service Manual Chapter 1. General Information12
Engine Model and Engine Serial
Number
Engine
Model Fuel Type Emission Regulation
G420FE LP/Dual Fuel EPA/CARB* 2007
Compliant
G420F LP/Gasoline/Dual
Fuel
* EPA: Environmental Protection Agency
* CARB: California Air Resources Board
G420FE Engine
•Comply with EPA 2007 Emission Regulation
•Electronic Control by ECM
•Certified LP/Dual Fuel System available
–Closed loop LP Carburetion system
–Closed loop MPI Gasoline system
•3-way Catalytic Muffler is standard
G420F Engine
•Not comply with EPA 2007 Emission Regulation
•Electronic Control by ECM
•Standard LP/Gas/DF/Dual Fuel System available
–Open loop LP Carburetion system
–Closed loop MPI Gasoline system
•Muffler is standard
Indication of Engine Model and Serial
Number
Engine Model Engine Serial Number
G420FE/G420F 30700001 to 39999999
Features and Benefits of G420FE/G420F Engine
•Al head with valve seat inserts
–Aluminum head and valve seat system
•DOHC 16 valve system
•Durable timing belt system
–Durable timing belt material and rubber-
sealed cover
•Distributorless Ignition system (coil on plug)
•Electronic control system by ECM
(Engine control module)
–Drive-by-wire system
–Higher efficiency and lower fuel consumption
–Min./Max. governor control
–Automatic engine protection from overheating
and/or low engine oil pressure
–Automatic transmission protection from
overheating
–Engine diagnostics by service-tool software
–Forklift ground speed limit (optional)

G420F(FE) Service Manual Chapter 1. General Information13
General Specification
G420FE Engine G420F Engine
GENERAL DESCRIPTION
ENGINE TYPE: Water-cooled, Inline 4-Cycle, 4-Cylinders
COMBUSTION SYSTEM: Semi-Rent Roof
INTAKE MANIFOLD Cast Aluminum (with injector ports)
EXHAUST MANIFOLD Cast Iron, Dry
VALVE CONFIGURATION: DOHC, 4 Valves per Cylinder
VALVE LIFTER/LASH ADJUSTER Hydraulic Lash Adjuster
VALVE ROTATOR Intake/Exhaust Rotator
CAMSHAFT DRIVE Timing belt system (25.4 mm Toothed Belt)
DISPLACEMENT: 1,975 cc (120.5 cid)
BORE x STROKE 82mm (3.23 in) x 93.5 mm (3.68 in)
BLOCK STRUCTURE Grey Cast Iron
HEAD STRUCTURE Aluminum with seat inserts
COMPRESSION RATIO: 9.4:1
COMPRESSION PRESSURE: 1,450 kPa (210 psi)
Intake Valve: 2° BTDC(Open)/ 16° ABDC(Close)
VALVE TIMING: Exhaust Valve: 6° BBDC(Open)/ 2° ATDC(Close)
FIRING ORDER: 1-3-4-2
WEIGHT: 170 kg (Dry)
ENGINE ROTATION: Counter-Clockwise (CCW) when viewed from Flywheel End
FUEL TYPE: LPG, Gasoline, Dual Fuel (LPG or Gasoline)
CRANK VENTILATION Foul Air System with PCV
IGNTION SYSTEM
IGNITION TYPE: Distributorless (coil on plug)
IGNITION TIMING: Electronic controlled by ECM
POWER TRANSISTOR Ignition coil driver
IGNITION COIL: 12 V operation volt, 4 coils (coil on plug)
SPARK PLUGS: Platimum Spark Plug (Air Gap: 0.8mm)
LUBRICATION SYSTEM
OIL PRESSURE: 167 kPa (24 psi) @ low Idle (90-100C oil temperature)
Upper Limit: 125°C (257°F)
Recommended: 99 - 110°C (210 - 230°F)
OIL TEMPERATURE: Lower Limit:80°C (176°F)
OIL PAN Cast Aluminum
OIL PAN CAPACITY 3.7 L (EXCLUDES OIL FILTER)
OIL FILTER: 0.3 L
ENGINE OIL SPECIFICATION: API - SJ, SAE 10W30 or SAE 5W30
COOLING SYSTEM
WATER PUMP ROTATION: V-Belt Drive - Clockwise (CW) when viewed from engine front
THERMOSTAT: Opening Temperature: 82°C (180°F)
Fully Open Temperature: 95°C (203°F)
COOLING WATER CAPACITY: 3.0 L (block only)

G420F(FE) Service Manual Chapter 1. General Information14
General Specification
G420FE Engine G420F Engine
LP FUEL SYSTEM
LP FUEL SYSTEM Closed loop LP Carburetion
System Open loop LP Carburetion System
MIXER: Diaphragm Type Air Valve Assembly inside, Downdraft
(Model: CA-100)
Diaphragm Type Air Valve
Assembly inside, Downdraft
(Model: CA-100)
REGULATOR: Two-Stage Negative Pressure
Regulator (Model: N-2007) Two-Stage Negative Pressure Regulator (Model: N-2001)
FUEL TRIM VALVE (FTV): Dual Dither System No FTV
FUEL FILTRATION: 40 Microns Maximum 40 Microns Maximum
GASOLINE FUEL SYSTEM
GASOLINE FUEL SYSTEM Closed loop MPI System and In-Tank Fuel Pump System
FUEL PUMP MODULE Electric Fuel Pump (12V)
Fuel Filter & Strainer
Gasoline Pressure Regulator (3.5 bar)
FUEL INJECTOR ASS’Y Electric Fuel Injector (12V)
ENGINE ELECTRIC
ENGINE CONTROL
MODULE(ECM): 12 V operation volt, 48 pins of I/O
CRANK SENSOR Magnetic Inductive type
CAM SENSOR Hall sensor
TMAP: Intake Air Temp. & Manifold Absolute Press. Sensor
PEDAL ANGLE SENSOR: Two-Output Signals (built in Accelerator Pedal)
Gasoline : One Oxygen sensor
OXYGEN SENSOR: Dual Oxygen Sensor System LPG: No Oxygen sensor
ECT-ECM: Engine Coolant Temperature Sensor for ECM
ECT-GAUGE Engine Coolant Temp. Sensor for GAUGE on Instrument Panel
TPS: Throttle Position Sensor (built in Throttle Body)
THROTTLE BODY: Electronic Throttle Body
LP FUEL LOCK-OFF: 12 V operation volt
ENGINE OIL PR. S/W: 28.4 kPa (4.1 psi)
STARTING MOTOR: 12 Volts, 1.7 kW
ALTERNATOR: 13.5 Volts, 90 Amp
EXHAUST SYSTEM
Muffler Catalytic Muffler Muffler (without catalyst)

G420F(FE) Service Manual Chapter 1. General Information15
Engine Power and Torque
G420FE Engine Power & Torque
FORKLIFT MODEL G(C)15/18S-5 G(C)20/25/30E-5
ENGINE MODEL G420FE-LP G420FE-DF(LP)
& G420FE-LP G420FE-DF(Gas)
RATED POWER Kw 33.6 39.5 39.5
hp 45 53 53
PS 46 54 54
rpm 2,400 2,550 2,550
MAX TORQUE N-m 147 157 157
lbf-ft 108 116 116
kgf-m 15,0 16.0 16.0
rpm 1600 1600 1600
GOVERNED SPEED rpm 2450 2600 2600
LOW IDLE rpm 750 750 750
G420F Engine Power & Torque
FORKLIFT MODEL G(C)15/18S-5
ENGINE MODEL G420F-DF(LP)
& G420F-LP G420F-DF(Gas) G420F-GAS
RATED POWER Kw 33.6 35.8 36.5
hp 45 48 49
PS 45.6 48.7 49.7
rpm 2,400 2,400 2,400
MAX TORQUE N-m 147 152 154
lbf-ft 108 112 114
kgf-m 15,0 15.5 15.7
rpm 1600 1600 1600
GOVERNED SPEED rpm 2450 2450 2450
LOW IDLE rpm 750 750 750
FORKLIFT MODEL G(C)20/25/30E-5
ENGINE MODEL G420F-DF(LP)
& G420F-LP G420F-DF(Gas) G420F-GAS
RATED POWER Kw 39.5 39.5 40.3
hp 53 53 54
PS 53.7 53.7 54.7
rpm 2,550 2,550 2,550
MAX TORQUE N-m 157 157 160
lbf-ft 116 116 118
kgf-m 16.0 16.0 16.3
rpm 1600 1600 1600
GOVERNED SPEED rpm 2600 2600 2600
LOW IDLE rpm 750 750 750

G420F(FE) Service Manual Chapter 2. Recommended Maintenance16
Chapter 2. RECOMMENDED MAINTENANCE
Suggested maintenance requirements for an engine equipped with an MI-07 fuel system are contained in this
section. The operator should, however, develop a customized maintenance schedule using the requirements
listed in this section and any other requirements listed by the engine manufacturer.
General Maintenance
Test Fuel System for Leaks
•Obtain a leak check squirt bottle or pump spray
bottle.
•Fill the bottle with an approved leak check solution.
•Spray a generous amount of the solution on the
fuel system fuel lines and connections, starting at
the storage container.
•Wait approximately 15-60 seconds, then perform a
visual inspection of the fuel system. Leaks will cause
the solution to bubble.
•Listen for leaks
•Smell for LPG odor which may indicate a leak
•Repair any leaks before continuing.
•Crank the engine through several revolutions. This
will energize the fuel lock-off and allow fuel to flow to
the pressure regulator/converter. Apply additional
leak check solution to the regulator/ converter fuel
connections and housing. Repeat leak inspection as
listed above.
•Repair any fuel leaks before continuing.
Inspect Engine for Fluid Leaks
•Start the engine and allow it to reach operating
temperatures.
•Turn the engine off.
•Inspect the entire engine for oil and/or coolant
leaks.
•Repair as necessary before continuing.
Inspect Vacuum Lines and Fittings
•Visually inspect vacuum lines and fittings for
physical damage such as brittleness, cracks and
kinks. Repair/replace as required.
•Solvent or oil damage may cause vacuum lines to
become soft, resulting in a collapsed line while the
engine is running.
•If abnormally soft lines are detected, replace as
necessary.
Inspect Electrical System
•Check for loose, dirty or damaged connectors and
wires on the harness including: fuel lock-off, TMAP
sensor, O2 sensors, electronic throttle, control
relays, fuel trim valves, crank position sensor, and
cam position sensor.
•Repair and/or replace as necessary.
Inspect Foot Pedal Operation
•Verify foot pedal travel is smooth without sticking.

G420F(FE) Service Manual Chapter 2. Recommended Maintenance17
Engine Oil Classification
Recommended API classification: Above SJ
Recommended SAE viscosity classification
The following lubricants should be selected for all
engines to enhance excellent performance and
maximum effect.
1. Observe the API classification guide.
2. Proper SAE classification number should be
selected within ambient temperature ranges. Do
not use the lubricant with SAE classification
number and API grade not identified on the
container.
*1. 10W-30 engine oil is recommended
If 10W-30 is not applicable, proper engine oil will be possible according to temperature ranges.

G420F(FE) Service Manual Chapter 2. Recommended Maintenance18
Checking Engine Oil Level
1. Check that the oil level is between “MIN” and
“Max” marks on the engine oil level gauge.
2. If the oil level is below “MIN” mark, add oil until
the level is within the specified ranges.
3. Check the engine for oil contamination and
viscosity and replace if necessary.
Replacing Engine Oil and Filter
CAUTION
Prolonged and repeated contact with mineral oil
will result in the removal of natural fats from the
skin, leading to dryness, irritation and dermatitis.
In addition, used engine oil contains potentially
harmful contaminants which may cause skin
cancer.
Exercise caution in order to minimize the length
and frequency of contact of your skin to used oil.
In order to preserve the environment, used oil
and used oil filter must be disposed of only at
designated disposal sites.
1. Drain engine oil.
1) Remove the oil filler cap.
2) Remove the oil drain plug, and drain the oil into
a container.
2. Replace oil filter.
1) Remove the oil filter.
2) Check and clean the oil filter installation
surface.
3) Check the part number of the new oil filter is as
same as old one.
4) Apply clean engine oil to the gasket of a new
oil filter.
5) Lightly screw the oil filter into place, and
tighten it until the gasket contacts the seat.
6) Tighten it an additional 3/4 turn.
3. Refill with engine oil filter.
1) Clean and install the oil drain plug with a new
gasket.
Torque 39.2~44.1N.m(4.0~4.5kgf.m,
28.9~32.5lb-ft)
2)Fill with fresh engine oil.
Capacity Drain
and refill 4.0L(4.23US qts, 3.52Lmp qts)
Oil filter 0.3L(0.32US qts, 0.26Lmp qts)

G420F(FE) Service Manual Chapter 2. Recommended Maintenance19
3) Install the oil filler cap.
4. Start engine and check for oil leaks.
5. Recheck engine oil level.
Checking Compressed Pressure
1. Prior to inspection, check that the engine oil,
starter motor and battery are normal.
2. Start the engine and run it until the engine coolant
temperature reaches 80 ~ 95°C.
3. Stop the engine and disconnect the ignition coil
and air cleaner element.
4. Remove the spark plug.
5. After opening the throttle valve completely, crank
the engine to remove foreign material from the
cylinder.
CAUTION
At this time, necessarily screen the spark plug
hole with a rag. Because hot coolant, oil, fuel,
and other foreign material, being penetrated in
the cylinder through cracks can come into the
spark hole during checking compressed
pressure.
When cranking the engine to test compressed
pressure, necessarily open the throttle valve be-
fore cranking.
6. Install the compression gauge to the spark plug
hole.
7. With the throttle valve opened, crank the engine
to measure the compressed pressure.
Standard 15kg/㎠
Standard(250~400rpm) Limit 14kg/㎠
8. Follow the procedures (no.6-7) to each cylinder
and check that compressed pressure values of all
cylinders are within the limit.
Limit 1.0kg/㎠
9. If any of all cylinders is out of limit, add a small
amount of engine oil to the spark plug hole, and
re-proceed the procedures (no.6-7) to the cylinder.
At this time, if the compressed pressure is increased,
it means that the piston, piston ring or cylinder
surface are worn or damaged, and if the
compressed pressure is decreased, it means that
the valve is clogged, the valve contact is faulty, or
the pressure leaks through gasket.
CAUTION
If a large amount of incomplete combustion
gaso-line comes into the catalytic converter,
emergency such as a fire can occur due to
overheating. So this job should be done quickly
with the engine not operated.