Doosan G420FE LP - User Manual

Questions and Answers

M
Michael JacksonAug 7, 2025
How to troubleshoot engine cranking but not starting in Doosan Lifting Systems (Gas)?
- G
  gmillsAug 8, 2025
  If your Doosan Lifting Systems engine cranks but won't start, several issues could be the cause. First, ensure the fuel tank isn't empty and is at least ¼ full. Other potential causes include a clogged fuel filter (repair or replace as needed), a faulty vapor connection (check for holes, loose clamps, or kinks), an electric fuel pump malfunction (check electrical connections, relay, and fuse), a malfunctioning fuel pressure regulator (test its operation), a malfunctioning fuel injector (test its operation), incorrect air/fuel or ignition/spark control (see Advanced Diagnostics), or no VR Sensor signal (verify the VR signal is present).
A
Adriana Simpson DDSAug 12, 2025
Why is my Doosan Lifting Systems difficult to start (Gas)?
- J
  Joshua SandersAug 12, 2025
  If your Doosan Lifting Systems experiences difficulty starting, it might be due to several reasons. Check if the fuel tank is almost empty, as this can cause fuel pump cavitations; ensure the tank is at least ¼ full. Other potential causes include a clogged fuel filter (repair or replace), an electric fuel pump malfunction (check connections, relay, and fuse, and verify the pump is operating), a malfunctioning pressure regulator (test its operation), a malfunctioning fuel injector (test its operation), or a clogged air filter (clean or replace as required). Also, incorrect air/fuel or ignition control could be the issue (see Advanced Diagnostics). For engine mechanical issues, consult the Engine Service Manual.
A
albert71Aug 20, 2025
Why does my Doosan Lifting Systems not accelerate or hesitate during acceleration (Gas)?
- J
  Jennifer LongAug 20, 2025
  If your Doosan Lifting Systems will not accelerate, hesitates during acceleration, or the engine stalls, first isolate the gasoline system by running the lift truck on LPG. Verify the LPG cylinder is full and the valve is open. If the problem does not exist in LPG mode, proceed with the corrective action steps below; if the problem also exists in LPG mode, the root cause is most likely something other than the fuel system. Other potential causes include a fuel tank that's nearly empty (ensure it's at least ¼ full), a clogged fuel filter (repair or replace), a pressure regulator malfunction (test its operation), or a fuel injector malfunction (test its operation).
H
Heather MorganAug 25, 2025
How to fix rough idle on Doosan Lifting Systems (Gas)?
- R
  Rachael RodriguezAug 26, 2025
  If your Doosan Lifting Systems has a rough idle, isolate the gasoline system by running the lift truck on LPG. Verify the LPG cylinder is full and the valve is open. If the problem does not exist in LPG mode, proceed with the corrective action steps below; if the problem also exists in LPG mode, the root cause is most likely something other than the fuel system. Other potential causes include a pressure regulator malfunction (test its operation), a clogged fuel filter (repair or replace), or a vacuum leak (check between mixer and throttle body, throttle body and intake manifold, and intake manifold and cylinder head).
M
Mary SavageAug 29, 2025
What causes poor high speed performance in Doosan Lifting Systems (Gas)?
- B
  brad58Aug 29, 2025
  To address poor high-speed performance in your Doosan Lifting Systems, start by isolating the gasoline system by running the lift truck on LPG. Verify the LPG cylinder is full and the valve is open. If the problem does not exist in LPG mode, proceed with the corrective action steps below; if the problem also exists in LPG mode, the root cause is most likely something other than the fuel system. Also check for a clogged fuel filter (repair or replace), a plugged fuel line (remove obstruction), a clogged air filter (clean or replace), a faulty vapor connection (check for holes, tight clamps, and kinks), a pressure regulator malfunction (test its operation). For incorrect ignition control, see Advanced Diagnostics & Engine Service Manual.
W
Wanda GomezSep 3, 2025
How to decrease high idle speed on Doosan Lifting Systems (Gas)?
- R
  Robert GarciaSep 3, 2025
  To troubleshoot high idle speed in your Doosan Lifting Systems, check the pedal return spring travel for binding. For incorrect idle speed control, see Advanced Diagnostics & Engine Service Manual.
A
Angel BeckerNov 15, 2025
What to do if Doosan Lifting Systems will not run continuously (Gas)?
- S
  Stacey KingNov 15, 2025
  If your Doosan Lifting Systems will not run continuously, begin by isolating the gasoline system by running the lift truck on LPG. Verify the LPG cylinder is full and the valve is open. If the problem does not exist in LPG mode, proceed with the corrective action steps below; if the problem also exists in LPG mode, the root cause is most likely something other than the fuel system. Other potential causes include a nearly empty fuel tank (ensure it's at least ¼ full), a clogged fuel filter (repair or replace), an electric fuel pump malfunction (check connections, relay, and fuse), a pressure regulator malfunction (test its operation), or a fuel injector malfunction (test its operation). For incorrect idle speed or ignition problems, see Advanced Diagnostics. For engine mechanical issues, co...

This document is a Service Manual for the G420FE LP/Dual Fuel Engine and the G420F LP/Gasoline Dual Fuel Engine, as well as various associated forklift models. The manual provides comprehensive information for the maintenance, inspection, and repair of these engines and their integrated management systems. It is dated April 2007 and carries the document number SB4241E00.

Function Description:

The manual serves as a technical guide for service personnel, offering detailed instructions and specifications necessary to diagnose, troubleshoot, and repair the G420FE and G420F engines. These engines are designed for use in forklifts, specifically the G15S-5, G18S-5, G20SC-5, GC15S-5, GC18S-5, GC20SC-5, G20E-5, G25E-5, G30E-5, GC20E-5, GC25E-5, GC30E-5, and GC33E-5 models. The G420FE engine operates on LP (Liquefied Petroleum) or as a dual-fuel system, while the G420F engine operates on LP or gasoline as a dual-fuel system. The manual covers all major engine components, electrical systems, and the Engine Management System (EMS), providing a holistic approach to engine service. It emphasizes safety throughout, with warnings and precautions to prevent injury or damage during service procedures.

Important Technical Specifications:

The manual details numerous technical specifications crucial for proper service. These include:

General Specifications: Found in Chapter 1, these provide fundamental data about the engine design and characteristics.
Torque Specifications: Chapter 1 and specific component sections list precise tightening torques for various fasteners, essential for correct assembly and preventing damage.
Recommended Lubricants and Capacities: Chapter 1 outlines the types and quantities of lubricants required for optimal engine performance and longevity.
Engine Model and Serial Number Information: Instructions are provided for identifying specific engine models and serial numbers, which are vital for ordering correct parts and accessing relevant service bulletins.
Engine Power and Torque: General performance characteristics are listed, giving an overview of the engine's capabilities.
Engine Mechanical System Specifications: Chapter 3 includes detailed specifications for components like the cylinder head, crankshaft, pistons, and timing belt system, covering dimensions, clearances, and tolerances.
Engine Electrical System Specifications: Chapter 4 provides specifications for the ignition system, charging system, and starting system, including voltage, resistance, and current values where applicable.
Engine Management System (EMS) Specifications: Chapter 5 details the specifications for various sensors, actuators, and the Engine Control Module (SECM), including operational parameters and diagnostic values. This includes information on the LPG fuel system, MPI gasoline system, electronic throttle system, ignition system, and exhaust system.
Compressed Pressure: Procedures for checking engine compression are outlined, with expected pressure ranges.
Coolant Concentration and Specific Gravity: Tables and procedures are provided for testing and adjusting coolant mixtures to ensure proper cooling and freeze protection.

Usage Features:

The manual is structured to facilitate efficient and accurate service operations.

Comprehensive Index: A detailed index allows users to quickly locate specific topics, from general maintenance to complex system diagnostics.
Step-by-Step Procedures: Many sections provide clear, step-by-step instructions for removal, inspection, assembly, and adjustment of components.
Illustrations and Diagrams: The manual likely includes numerous illustrations, exploded views, and wiring diagrams to aid in understanding component locations, assembly sequences, and electrical connections. For example, "SECM Wiring Diagrams for G420FE" and "SECM Wiring Diagrams for G420F" are explicitly mentioned.
Troubleshooting Guides: Dedicated sections, such as "Troubleshooting" for the starting system and charging system, help service technicians diagnose common issues by outlining symptoms and potential causes.
Special Tools Information: The "Special Tools" section in Chapter 3 indicates that specific tools may be required for certain procedures, ensuring that technicians use the correct equipment.
Safety Information: An "Important Safety Information" section at the beginning emphasizes the importance of safety precautions, warning labels, and proper training, highlighting potential hazards and how to avoid them. It also clarifies that DOOSAN cannot anticipate every potential hazard and that users must ensure safety when using unrecommended procedures.
Information Accuracy Statement: The manual states that the information is based on data available at the time of writing and that specifications can change. It advises obtaining the most current information from DOOSAN dealers.

Maintenance Features:

Chapter 2, "RECOMMENDED MAINTENANCE," is dedicated to routine service tasks, ensuring the longevity and reliable operation of the engines.

General Maintenance: Covers fundamental checks such as testing the fuel system for leaks, inspecting for fluid leaks, checking vacuum lines and fittings, inspecting the electrical system, and verifying foot pedal operation.
Engine Oil Management: Includes procedures for checking engine oil level, understanding engine oil classification, and replacing engine oil and filter.
Cooling System Maintenance: Details coolant recommendations, checking coolant level, inspecting coolant hoses, checking for coolant leaks, and performing specific gravity tests to determine coolant concentration.
Drive Belt Maintenance: Instructions for checking and adjusting drive belt tension and inspecting the belt for damage.
Ignition System Maintenance: Covers inspecting the battery system, ignition system, ignition timing, and spark plugs.
Fuel System Maintenance: Provides guidance on replacing LP fuel filter elements, testing fuel lock-off operation, inspecting the pressure regulator/converter, inspecting the air/fuel valve mixer assembly, checking for intake leaks, inspecting the throttle assembly, and checking the TMAP sensor.
Exhaust System Maintenance: Includes procedures for inspecting the engine for exhaust leaks.
Maintenance Schedule: A dedicated "Maintenance Schedule" section (page 31) would outline the recommended intervals for various service tasks, helping users plan and execute preventive maintenance effectively. This proactive approach helps prevent major breakdowns and ensures optimal engine performance.