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Doosan G25P-3 - Service Manual

Doosan G25P-3
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G430 LP Engine
Standard Version
Low Emission Version
G20P-3, G25P-3, G30P-3
GC20P-3, GC25P-3, GC30P-3
SB4005E01
Oct. 2001
Service Manual

Table of Contents

Questions and Answers

  • K
    Kelly WrightAug 13, 2025
    Why is there no spark in my Doosan Engine?
    • L
      laurajonesAug 13, 2025
      If your Doosan Engine has no spark, it could be due to several reasons. Start by inspecting and replacing the distributor cap or spark plug leads if they are arcing. Also, replace the spark plugs if they are fouled, burned, or have cracked porcelain. Check the battery and electrical connections, and replace the spark plug wires if they are broken or have faulty insulation. If these steps don't solve the problem, replace the ignition switch or inspect and replace any other faulty ignition components. Clean or replace the distributor cap if it is cracked or dirty. Finally, disconnect the tachometer and test again to rule out a shorted tachometer.
  • A
    Anthony PaulAug 17, 2025
    Why is my Doosan Engine spark knocking?
    • A
      Amy TaylorAug 18, 2025
      If your Doosan Engine is experiencing spark knock, it could be due to several reasons. First, try retarding the ignition timing. If that doesn't solve the problem, switch to a higher quality fuel. Also, inspect the cooling system to ensure the engine isn't running hot. Finally, clean the engine to remove any carbon deposits.
  • E
    Elizabeth WhiteAug 20, 2025
    What to do if the Doosan Engine will not crank over?
    • M
      Mario SnyderAug 21, 2025
      If your Doosan Engine won't crank over, there are several potential causes. Start by charging the battery and checking the wiring for damage or loose connections. If that doesn't work, check if the circuit breaker has tripped and reset it if necessary. Other possible issues include a bad ignition switch, a bad starter solenoid, or a defective starter motor, all of which would need to be replaced.
  • L
    leealisonAug 25, 2025
    How to fix poor engine idle on a Doosan G25P-3 Engine?
    • L
      Lori MccarthyAug 26, 2025
      To fix a poor engine idle on your Doosan Engine, begin by checking the air breather for clogs and clean or replace it as needed. Then, adjust the idle-fuel mixture. Inspect and replace any faulty spark-plug wires that may be arcing. Other solutions include using higher grade fuel, adjusting the ignition timing, or replacing the spark plugs. You may also need to replace the ignition coil, clean or replace the distributor cap, or clean the carburetor. Repair any leaks at the intake manifold or carburetor base. If these steps don't resolve the issue, perform a compression check. Finally, tighten or replace the distributor if it is loose or worn, and inspect and replace any damaged components such as the head gasket, exhaust manifold, cracked head, or valve seat.
  • R
    randyfryeAug 28, 2025
    Why is my Doosan G25P-3's alternator noisy?
    • B
      Benjamin RoseAug 28, 2025
      A noisy alternator in your Doosan Engine can stem from several causes. Begin by tightening the mounting bolts. If the noise persists, replace the drive belt if it's worn, frayed, or loose. Additionally, tighten the drive pulley. If the issue continues, consider replacing or cleaning the bearings if they are worn or dirty. Lastly, replace the defective diode trio or stator if they are faulty.
  • U
    uhayesSep 1, 2025
    What causes malfunctioning instruments or gauges in a Doosan G25P-3 Engine?
    • A
      Alexis GuerreroSep 1, 2025
      Malfunctioning instruments or gauges in your Doosan Engine can be caused by faulty wiring, loose, or corroded terminals, so check and repair the wiring. Other potential causes include a bad key switch, a faulty gauge, or a faulty sender, all of which would need to be replaced.
  • S
    Sharon BarrettSep 5, 2025
    What causes noise around the valve cover area on a Doosan Engine?
    • C
      christinaandersonSep 5, 2025
      Noise around the valve cover area of your Doosan Engine can be due to several factors. It could be that the rocker arm is striking the valve cover, in which case you should adjust the rocker arm. Alternatively, the rocker arm might be out of adjustment, requiring you to re-adjust it. Other potential causes include a worn rocker arm, a bent push rod, or a collapsed lifter, all of which would need to be replaced.
  • V
    Victoria GonzalezSep 8, 2025
    Why is there water found on top of the pistons in my Doosan Engine?
    • J
      jgonzalezSep 8, 2025
      If you find water on top of the pistons in your Doosan Engine, it could be due to a cracked exhaust manifold (if water cooled), which would need to be replaced. Another cause could be improper installation of the manifold-to-elbow gasket (if water cooled); reinstall it properly. Also, check for and tighten any loose cylinder head bolts. Other potential causes include a blown cylinder head gasket, a cracked valve seat or porous/cracked casting, all of which would need to be inspected and replaced.

Summary

General Information

Shop Safety

Essential safety practices for working on engines and fuel systems.

General Description & Operation

Overview of engine components and their operational functions.

Tools and Equipment

Listing and description of special tools required for engine service.

Specifications

Technical Data

General engine specifications including type, displacement, bore, and stroke.

Engine Mechanical Data

Detailed mechanical specifications for fasteners and components.

Maintenance

Engine Crankcase Oil

Recommendations for engine oil type, viscosity, and capacity.

Cooling System

Procedures for checking coolant level and system inspection.

Maintenance Schedule

Recommended maintenance intervals based on hours or time.

Troubleshooting

Engine Performance

Diagnosing issues related to poor engine idle or acceleration.

Engine Starting Problems

Identifying causes for no spark or engine not cranking.

Engine Noise

Diagnosing various engine noises and their potential causes.

Engine Overheating

Identifying causes of engine overheating, mechanical or cooling system related.

LP Fuel system (Sandard and;or Low Emission Version)

Troubleshooting common issues with the LP fuel system.

Starting System

General Description

Explanation of the starting motor and solenoid function.

Diagnosis Procedure

Step-by-step guide to diagnose starting system issues.

Starting Motors

Specifications and coverage information for starting motors.

Charging System

General Description

Overview of the alternator's function in charging the battery.

Alternators

Details on alternator types, coverage, and specifications.

Remove & Install Alternator

Procedure for removing and installing the alternator assembly.

Ignition System

High Energy Ignition Systems

Description of HEI system benefits and improvements.

Electronic Spark Timing (EST) Distributor

Details on the EST distributor used in G430 engines.

Delco Electronic Spark Timing (EST) Distributor Service

Procedures for testing and servicing EST distributor components.

LP Fuel System

Carburetor

Explanation of the air valve type carburetor operation.

Tests or Adjustments

Procedures for carburetor idle speed and mixture adjustments.

Fuel System Leak Check

Methods for checking the fuel system for leaks.

LP FUEL SYSTEM (LOW EMISSION VERSION)

Pressure Regulator;Vaporizer

Description of the two-stage pressure regulator/vaporizer.

Variable Venturi Air;Fuel Mixer

Explanation of the mixer's operation and air/fuel mixture control.

Engine Control Unit (ECU)

Role of the ECU in controlling air/fuel ratio using sensors.

Governor System

General Description

Explanation of governor function in maintaining constant engine speed.

Governor Operation

Description of governor function under different load conditions.

Adjustment Procedures

Steps for adjusting engine speed and addressing surging.

Lubrication System

General Description

Overview of the engine lubrication system and oil flow.

Lubrication System Problems

Common lubrication system issues like oil consumption and pressure.

Oil Pressure Check

Procedure for measuring and checking engine oil pressure.

Cooling System

General Description

Explanation of the pressure-type cooling system.

Cooling System Tests

Tests to diagnose cooling system problems including pressure and temperature.

Thermostat

Description and testing procedure for the engine thermostat.

Water Pump Replacement

Procedure for removing and installing the water pump.

Base Engine Service Procedure

Draining Fluids and Oil Filter Removal

Steps for draining engine fluids and removing the oil filter.

Cylinder Head Removal

Procedure for removing the engine cylinder head.

Piston, Connecting Rod and Bearing Removal

Steps for removing pistons, connecting rods, and bearings.

Crankshaft and Bearings Clean and Inspect (Connecting Rod Bearing Clearance)

Procedure for cleaning and inspecting connecting rod bearings.

Piston, Connecting Rod and Bearing Installation

Steps for installing pistons, connecting rods, and bearings.

Cylinder Head Installation

Procedure for installing the engine cylinder head.

Special Toos and Equipment

ITK-1 Pressure Gauge Kit

Description of the pressure gauge kit for fuel system testing.

FSA-1000 Fuel System Analyzer (Low Emission Version Only)

Analyzer for checking air/fuel mixture in low emission systems.

Doosan G25P-3 Specifications

General IconGeneral
Displacement2.4 L
Fuel TypeLPG
Engine ModelG424
AspirationNaturally Aspirated
Cooling SystemWater-cooled
Net Power24.8 kW (33.2 hp)

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