Doosan G420FE User Manual (English)

Questions and Answers:

T
Tracy WhiteheadAug 16, 2025
What to do if Doosan G420FE Engine has low oil pressure?
- C
  Cynthia CookAug 16, 2025
  If your Doosan Engine has low oil pressure, there are several potential causes and solutions: * Check the engine oil level, as insufficient oil can cause low pressure. * A defective oil pressure switch can also be the culprit, so consider replacing it. * A clogged oil filter can restrict oil flow; install a new filter. * Worn oil pump gear or cover should be replaced. * Using thin or diluted engine oil? Replace the engine oil. * Inspect or replace the oil relief valve if it's clogged open. * Excessive bearing clearance requires bearing replacement.
M
Mary AndersonAug 19, 2025
Why is my Doosan G420FE oil pressure high?
- P
  pjenkinsSep 12, 2025
  High oil pressure in your Doosan Engine is likely due to an oil relief valve clogged in the closed position. Repair the relief valve to resolve this.
M
mwilliamsonAug 22, 2025
How to fix Doosan G420FE Engine oil cooling system leak?
- E
  Elizabeth CabreraAug 22, 2025
  If your Doosan Engine has an oil cooling system leak, check for loose connecting parts and retighten them. Also, inspect hoses, pipes, and the oil cooler for cracks or damage and replace if necessary.
S
Susan BautistaAug 25, 2025
Why is my Doosan Engine coolant temperature abnormally high?
- M
  Marcus HillAug 26, 2025
  An abnormally high coolant temperature in your Doosan Engine can stem from several issues. The thermostat or radiator cap might be defective and need replacement. There could be abnormal flow in the cooling system, requiring cleaning or replacement of parts. A loose or missing driving belt needs correction or replacement. Check for a loose water pump, and repair or replace if necessary. Defective water temperature wiring should be repaired or replaced. A defective cooling pan should be replaced. If the radiator or thermostat switch is defective, add coolant. Also, adding coolant is the solution if the coolant is inefficient.
N
Nancy GordonAug 27, 2025
How to fix a Doosan G420FE exhaust gas leak?
- C
  Christopher WilliamsonAug 27, 2025
  If you have an exhaust gas leak in your Doosan Engine, start by checking for loose connecting parts and retighten them. Also, inspect the pipe or muffler for damage; repair or replace as needed.
J
Jessica WilliamsAug 30, 2025
What causes low compression in a Doosan Engine?
- C
  cmooreAug 30, 2025
  Low compression in a Doosan Engine can be attributed to several factors: * A damaged cylinder head gasket, which requires replacement. * Worn or damaged piston rings, also requiring replacement. * Worn piston or cylinder, necessitating repair or replacement of the piston and cylinder block. * Worn or damaged valve seat, which means you should repair or replace the valve and seat ring.
B
Brittany ClineSep 2, 2025
How to fix a noisy valve in Doosan G420FE Engine?
- M
  Matthew Dixon DDSSep 2, 2025
  A noisy valve in your Doosan Engine can be due to several reasons. If the engine oil is thin or diluted, replace it. A faulty HLA (Hydraulic Lash Adjuster) may also be the cause and should be replaced. Lastly, a worn belt stem or valve guide can cause noise, so replace them if necessary.
M
Mariah RomeroSep 4, 2025
What to do if Doosan Engine has abnormally low coolant temperature?
- P
  petersstaceySep 5, 2025
  If your Doosan Engine shows an abnormally low coolant temperature, it could be due to a defective thermostat, which should be replaced. Another possible cause is defective water wiring, which needs repair or replacement.
B
Brittany BeckSep 7, 2025
How to fix a Doosan G420FE Engine timing belt that is noisy?
- M
  mwolfSep 7, 2025
  If your Doosan Engine's timing belt is noisy, it's likely due to incorrect belt tension. Correct the belt tension to resolve the issue.
Q
qparkerSep 10, 2025
What causes a Doosan G420FE to have a low coolant level?
- J
  John VelazquezSep 12, 2025
  A low coolant level in your Doosan Engine can be caused by several factors: * Coolant leaks from the heater or radiator hose, which require repair or replacement of the parts. * A defective radiator cap, in which case you should retighten the clamp or replace the cap. * Issues with the thermostat housing, necessitating replacement of the gasket or housing. * A faulty radiator, which should be replaced. * A malfunctioning water pump, requiring replacement of parts.

Doosan G420FE Specifications

General

Engine Model	G420FE
Number of Cylinders	4
Compression Ratio	17.5 : 1
Aspiration	Turbocharged
Fuel Type	Diesel
Emission Compliance	Tier 4 Final

Summary

Chapter 1. General Information

Precautions before Service

General safety precautions before performing service on the engine.

Tightening Torque

Specifies torque values for standard parts to ensure proper assembly.

Recommended Lubricants and Capacities

Details recommended lubricants and their capacities for engine systems.

Engine Model and Engine Serial Number

Information on identifying engine models and serial numbers.

General Specification

Provides key technical specifications for engine models.

Engine Power and Torque

Lists power and torque ratings for different engine configurations.

Chapter 2. Recommended Maintenance

Test Fuel System for Leaks

Procedure for checking the fuel system for leaks using leak check solution.

Inspect Engine for Fluid Leaks

Procedure to inspect the engine for oil and coolant leaks.

Inspect Vacuum Lines and Fittings

Visual inspection of vacuum lines and fittings for damage.

Inspect Electrical System

Checks for loose/damaged connectors and wires in the electrical system.

Inspect Foot Pedal Operation

Verifies smooth and non-sticking travel of the foot pedal.

Engine Oil Classification

Details recommended API and SAE classifications for engine oil.

Checking Engine Oil Level

Procedure to check engine oil level using the dipstick.

Replacing Engine Oil and Filter

Step-by-step instructions for changing engine oil and filter.

Checking Compressed Pressure

Procedure to measure cylinder compression pressure for engine health.

Adjusting Timing Belt Tension

Steps for adjusting the timing belt tension to specification.

Cooling System Maintenance

Procedures for maintaining the engine's cooling system.

Checking and Adjusting Drive Belt

Procedures for checking and adjusting the drive belt tension.

Ignition System Maintenance

Maintenance procedures for the engine's ignition system.

Fuel System Maintenance

Maintenance procedures for the fuel system, including filter replacement.

Chapter 3. Engine Mechanical System

Engine Outline

Provides an overview and illustration of the engine's external components.

Specifications

Details technical specifications for engine components like bore, stroke, etc.

Torque Specification

Lists torque values for various engine mechanical components.

Special Tools

Lists and illustrates special tools required for engine disassembly/assembly.

Troubleshooting

Provides a guide for diagnosing engine mechanical problems and their causes/remedies.

Timing Belt System

Covers components, removal, inspection, and assembly of the timing belt system.

PCV Valve

Explains the outline, operation, service procedures, and troubleshooting of the PCV valve.

Intake and Exhaust System

Details the components and procedures for the intake and exhaust manifold systems.

Cooling System

Explains the general description, testing, and adjusting of the cooling system.

Chapter 4. Engine Electrical System

Specifications

Lists specifications for ignition coil, spark plug, starter motor, and alternator.

Ignition System

Details the MI-07 ignition system, its components, and operation.

Coil-On-Plug Ignition System

Explains the coil-on-plug ignition system and its components.

Misfires

Discusses common misfire issues in COP ignition systems and their causes.

COP Checks

Outlines checks for coil-on-plug ignition system components.

Inspection of Ignition Timing

Procedures for inspecting and measuring ignition timing.

Inspection of Ignition Coil Drivers (Power TR)

Details the inspection of ignition coil drivers and their location.

Inspection of Ignition Coil

Procedures for inspecting ignition coils for resistance and proper operation.

Inspection of Spark Plug

Steps for inspecting and cleaning spark plugs, including clearance checks.

Charging System

General description of the charging system and alternator types.

Troubleshooting

Provides a troubleshooting guide for charging system defects.

Troubleshooting Procedure

Step-by-step procedures for troubleshooting charging system issues.

Drop of Electric Pressure Test of Alternator Output Wire

Procedure to test the alternator output wire connection.

Output Current Test

Procedure to test the alternator's output current against rated values.

Disassembly and Installation

Steps for disassembling and installing the alternator assembly.

Removal and Installation

Procedures for removing and installing the alternator and its components.

Disassembly

Steps for disassembling the alternator assembly.

Inspection

Inspection procedures for the alternator rotor and stator components.

Starting System

General description of the starting motor, solenoid, and overrunning clutch.

Diagnosis Procedure

Procedures for diagnosing starting system problems.

Start Relay Tests

Tests for the start relay to determine its functionality.

Troubleshooting

Troubleshooting guide for various starting system symptoms.

Starter

Lists components of the starter motor assembly.

Removal and Installation

Procedures for removing and installing the starter motor assembly.

Inspection (After Removal)

Inspection procedures for the starter motor assembly after removal.

Hold in Test of Solenoid

Test procedure for the solenoid's hold-in function.

Return Test of Solenoid

Test procedure for the solenoid's return function.

Performance Test (with NO-LOAD)

Test for starter motor performance without load.

Disassembly

Steps for disassembling the starter motor assembly.

Inspection (After Disassembly)

Inspection procedures for starter motor armature and field coils.

Brush Holder

Checks for continuity in the brush holder.

Overrunning Clutch

Inspection of the overrunning clutch for wear and damage.

Brush Replacement

Procedure for replacing worn starter motor brushes.

Installation of Rear Bracket

Procedure for installing the rear bracket and bushing.

Chapter 5. Engine Management System (EMS)

General Information

Provides an overview of the MI-07 EMS for G420FE engines.

Specifications

Details SECM and sensor/switch input specifications.

SECM and Sensor/Switch Inputs

Lists SECM components and their input specifications.

G420FE EMS (Engine Management System) Overview

Overview of the MI-07 Dual Fuel System for G420FE engine.

LPG Fuel System Operation

Describes the operation of the MI-07 system on an LPG fuel system.

Dual Dither Valve

Explains the function of the dual dither valve in emissions control.

Regulator Pressure Offset

Details how regulator pressure offset is achieved.

SECM

General description of the Small Engine Control Module (SECM).

MI-07 LP Fuel Filter

Information on the MI-07 LP fuel filter's function and replacement.

MI-07 Fuel Lock-Off (Electric)

Explanation of the electric fuel lock-off valve's operation and safety features.

N-2007 Pressure Regulator/Vaporizer

Description of the N-2007 pressure regulator/vaporizer functions.

N-2007 Operation

Detailed operational principles of the N-2007 regulator.

CA100 Mixer

Description of the CA100 mixer's installation and function.

CA100 Mixer Operation

Explains how the CA100 mixer operates with the engine and SECM.

Idle Mixture Adjustment

Procedure for adjusting the idle mixture screw on the CA100 mixer.

Fuel Trim Valve (FTV)

Explanation of Fuel Trim Valve operation and SECM control.

MPI Gasoline System Operation

Details the multi-point injection system for gasoline operation.

Electronic Throttle System

Explanation of the electronic throttle control system.

Ignition System

Details the MI-07 ignition system and its components.

Exhaust System

Information on heated exhaust gas oxygen sensors (HEGO).

SECM

General description of the Small Engine Control Module (SECM).

SECM Wiring Diagrams for G420FE

Provides wiring diagrams for the SECM.

EMS Inspection and Repair

Procedures for inspecting and repairing the Engine Management System.

Engine Control Module (SECM)

Details SECM specifications, inputs, outputs, and functionality.

Analog Inputs

Lists analog inputs used by the SECM for various sensors.

Frequency/Position Inputs

Lists frequency and position inputs for crankshaft and camshaft sensors.

Digital Inputs

Lists digital inputs for switches and sensors.

Outputs

Lists the outputs controlled by the SECM, such as injectors and throttle.

Camshaft Position Sensor

Details the camshaft position sensor's location, description, and inspection.

Crank Shaft Position Sensor

Details the crankshaft position sensor's location, description, and inspection.

MAP (Manifold Absolute Pressure) Sensor

Details the MAP sensor's function, circuit, and inspection.

IAT (Intake Air Temperature) Sensor

Details the IAT sensor's function, circuit, and inspection.

Oxygen Sensor (Pre-Catalyst)

Details the pre-catalyst oxygen sensor's location, description, and specification.

Oxygen Sensor (Post-Catalyst)

Details the post-catalyst oxygen sensor's location, description, and specification.

ECT (Engine Coolant Temperature) Sensor

Details the ECT sensor's location, description, and inspection.

LP Fuel Temperature Sensor

Details the LP fuel temperature sensor's location, description, and inspection.

Angle Sensor-Accelerator

Details the accelerator pedal sensor's location, description, and inspection.

Transmission Oil Temperature Switch

Details the transmission oil temperature switch's location, description, and inspection.

Ground Speed Limit Switch (optional)

Details the ground speed limit switch's function and inspection.

Electronic Throttle Body

Details the electronic throttle body's location, description, and inspection.

Chapter 6. LPG Fuel Delivery System

G420FE LP System Inspection and Repair

Procedures for inspecting and repairing the G420FE LPG fuel system.

Removal and Installation

Safety warnings and general guidance for removal/installation.

Hose Connections

Diagrams and notes for proper routing of vacuum and fuel lines.

Certified System Connections

Diagrams showing certified system hose connections.

Removal and Installation of N-2007 LP Regulator

Procedures for removing and installing the N-2007 LP regulator.

N-2007 Regulator Removal Steps

Step-by-step instructions for removing the N-2007 regulator.

N-2007 Installation Steps

Step-by-step instructions for installing the N-2007 regulator.

Removal and Installation of CA100 Mixer for G420FE

Procedures for removing and installing the CA100 mixer for G420FE.

CA100 Certified Mixer Removal Steps

Step-by-step instructions for removing the CA100 mixer.

Tests and Adjustments

Safety warnings and guidance for tests and adjustments.

CA100 Certified Mixer Installation Steps

Step-by-step instructions for installing the CA100 mixer.

N-2007 Regulator Service Testing

Tests for checking the N-2007 regulator/converter operation.

Break-Off Test

Test procedure for the secondary stage of the N-2007 regulator.

Pressure Test

Test procedures for the primary stage of the N-2007 regulator.

AVV (Air Valve Vacuum) Testing

Test procedure for checking air valve vacuum on the CA100 mixer.

Ignition Timing Adjustment

Procedure for adjusting ignition timing using the MI-07 service tool.

Connection of the MI-07 Service Tool

Steps for connecting the MI-07 service tool for diagnostics.

Idle Mixture Adjustment

Procedure for adjusting idle mixture on the CA100 mixer with O2 sensor.

G420F LP Fuel Systems Without O2 Sensor

Idle adjustment procedure for G420F LP systems without O2 sensor.

Power Valve Adjustment

Procedure for adjusting the power valve on the mixer.

Parts Description

Parts list and exploded view for the CA100 mixer.

Exploded View of CA100 Mixer (Certified)

Exploded view illustration of the CA100 mixer.

Parts Description

Parts list for the N-2007 regulator.

Exploded View of N-2001 Regulator (Certified)

Exploded view illustration of the N-2001 regulator.

N2001 Regulator Disassembly Steps

Step-by-step instructions for disassembling the N2001 regulator.

N2001 Disassembled Service

Cleaning and inspection procedures for disassembled N2001 regulator parts.

Chapter 7. MPI Gasoline Fuel Delivery System

Specification

Lists specifications for MPI gasoline fuel system components.

Special Tools

Lists and illustrates special tools for fuel pressure testing.

Components Location

Identifies the location of MPI gasoline fuel system components.

Fuel Pressure Test

Procedures for testing fuel pressure and fuel leakage.

Injector

Details the injector's location, description, and specifications.

Injector Inspection

Procedures for inspecting injectors for operation and resistance.

Fuel Pump

Procedures for removal and installation of the fuel pump assembly.

Chapter 8. Basic Troubleshooting

Preliminary Checks

Initial checks before starting troubleshooting for MI-07 systems.

Before Starting

Steps to verify SECM and MIL light operation before starting.

Visual/Physical check

Guides for performing visual and physical checks on the system.

Basic Troubleshooting Guide

Customer problem analysis sheet for basic troubleshooting.

Basic Inspection Procedure

General inspection procedures for electronic parts resistance.

Intermittent Problem Inspection Procedure

Procedures for diagnosing intermittent problems by simulating conditions.

Connector Inspection Procedure

Guidelines for handling and inspecting electrical connectors.

Wire Harness Inspection Procedure

Procedures for inspecting the wire harness for damage or issues.

Electrical Circuit Inspection Procedure

Procedures for checking electrical circuits for open circuits.

Check Short Circuit

Procedures for checking electrical circuits for short circuits.

Symptom Troubleshooting Guide Chart for MPI Gasoline Engine

Troubleshooting guide based on engine symptoms for MPI gasoline engines.

Engine Is Not Starting

Troubleshooting steps when the engine fails to start.

Engine Is Difficult To Start(Cranking OK)

Troubleshooting steps when the engine cranks but won't start.

Irregular Idling Or Engine Is Suddenly Stopped

Troubleshooting steps for irregular idling or engine stalling.

Engine Hesitation Or Insuffient Accelelation

Troubleshooting steps for engine hesitation or poor acceleration.

Detonation / Spark Knock

Troubleshooting guide for detonation or spark knock symptoms.

Backfire

Troubleshooting guide for backfire issues in the intake or exhaust system.

Dieseling, Run-on

Troubleshooting guide for engine run-on after the key is turned off.

Rough, Unstable, Incorrect Idle, or Stalling

Troubleshooting guide for rough idle, unstable idle, or stalling issues.

Cuts Out, Misses

Troubleshooting guide for engine cutting out or missing.

Poor Fuel Economy / Excessive Fuel Consumption LPG Exhaust Smell

Troubleshooting guide for poor fuel economy and LPG exhaust smell.

High Idle Speed

Troubleshooting guide for high idle speed conditions.

Excessive Exhaust Emissions or Odors

Troubleshooting guide for excessive exhaust emissions or odors.

Diagnostic Aids for Rich / Lean Operation

Diagnostic aids for identifying rich or lean fuel conditions.

Chart T-1 Restricted Exhaust System Check

Procedure for checking the exhaust system for restrictions.

Chapter 9. Advanced Diagnostics

Reading Diagnostic Fault Codes

Explains how to retrieve diagnostic fault codes from the SECM.

Displaying Fault Codes (DFC) from SECM Memory

Procedure to enter SECM memory to display diagnostic fault codes.

Clearing Fault (DFC) Codes

Procedure to clear stored diagnostic fault codes from SECM memory.

Fault Action Descriptions

Descriptions of specific actions taken by the SECM for detected faults.

Fault List Definitions

Definitions of various fault types related to sensors and system inputs.

Table 1. Fault List Definitions

Detailed definitions of specific faults related to APP sensors and their codes.

Table 1. Fault List Definitions (cont’d.)

Continued definitions of fault lists for various sensors and system inputs.

Table 1. Fault List Definitions (cont’d.)

Continued definitions of fault lists for various sensors and system inputs.

Table 1. Fault List Definitions (cont’d.)

Continued definitions of fault lists for various sensors and system inputs.

Table 1. Fault List Definitions (cont’d.)

Continued definitions of fault lists for various sensors and system inputs.

Table 1. Fault List Definitions (cont’d.)

Continued definitions of fault lists for various sensors and system inputs.

Table 1. Fault List Definitions (cont’d.)

Continued definitions of fault lists for various sensors and system inputs.

Table 1. Fault List Definitions (cont’d.)

Continued definitions of fault lists for various sensors and system inputs.