Installation Procedure for Dongfeng 24V Starter Motor

I. Preparation and Safety (Mandatory Pre-installation Steps)

1. Safety Operations: Park the vehicle on a level surface, engage the parking brake and place wheel chocks. Disconnect the main negative terminal of the battery (the short-circuit risk of 24V system is higher) and set the ignition switch to the OFF position.

2. Tool List: Socket/box-end wrenches, torque wrench, wire cutters, cleaning cloths, anti-seize grease, multimeter, insulating tape/sleeves, and wire harness clips.

3. Parts Verification: Ensure the model of the new starter motor matches the vehicle/engine. Check that the drive gear, shift fork, magnetic switch and wire harness connectors are intact. Confirm the 24V specification is correct and prioritize the use of original equipment manufacturer (OEM) parts.

4. Mounting Surface Cleaning: Remove the dust cover/guard plate, clean oil stains and rust on the mounting surface. Apply anti-seize grease if necessary to ensure a tight fit without looseness.

II. Installation Procedures (Perform in Sequence)

1. Positioning and Fastening (Prevent Misalignment/Abnormal Noise)

1. Push the starter motor into the mating surface of the engine and transmission, align it with the mounting holes, insert the fixing bolts (usually 2–3 pieces), and perform initial pre-tightening without final tightening.

2. Tighten the bolts step by step/diagonally in accordance with vehicle specifications:

• Main Fixing Bolts: 28–35 N·m for mainstream models (37–45 N·m for heavy-duty vehicles). Violent tightening with an air impact wrench is strictly prohibited.

• Shift Fork/Auxiliary Fixing Bolts: 12–15 N·m to ensure the shift fork moves without jamming.

3. Check the alignment between the drive gear and the flywheel ring gear to ensure no interference. Adjust the positioning pin/guide sleeve if necessary.

2. Electrical Connection (Prevent Reverse Connection and Burnout)

• Reversing the positive and negative poles of the 24V system is strictly prohibited.

• Torque for wire harness clip bolts: 7–10 N·m to avoid vibration and wear.

3. Accessory Assembly and Adjustment (Prevent Jamming/Slippage)

1. Install the dust cover and heat shield according to the original factory marks to ensure no interference with the movement of the shift fork and gear.

2. Check Drive Gear Lubrication: Apply a small amount of high-temperature resistant grease only to the bearings. Never apply grease to the gear tooth surfaces (to prevent meshing slippage).

3. Manually press the shift fork to confirm the gear extends and retracts smoothly without jamming, and the shift fork return spring is effective.

4. Finalization and Pre-power-on Inspection

1. Recheck the bolt torque, wire connections and gear alignment to confirm no errors. Reinstall the guard plate/dust cover.

2. Reconnect the negative terminal of the battery and ensure the connection is secure.

III. Core Parameters and Taboos (Key Safeguards)

• It is strictly prohibited to plug/unplug the Terminal 50 control wire or short-circuit the Terminal 30 in the power-on state.

• Connecting a 12V power supply to the 24V system is strictly prohibited, which will cause insufficient magnetic force and starting failure.

IV. Testing and Verification (Mandatory Post-installation Steps)

1. Static Test: Turn the ignition key to ON without starting the engine. Measure the voltage of Terminal 30 (≈ 24V). Terminal 50 should have no voltage when OFF and ≈ 24V when ON.

2. Dynamic Test: Start the engine and observe that the starter motor runs without gear tooth impact or abnormal noise, and the gear retracts timely after starting. Do not start continuously more than 3 times, with an interval of ≥ 2 minutes between each start.

3. Load Test: Measure the voltage (≥ 22V) after starting to confirm the current is normal. Check that the wire harness/terminals have no overheating (temperature ＜ 60℃).

Core Precautions for Installing Dongfeng 24V Starter Motor

I. Power Disconnection and Safety (Higher Risk for 24V Systems, Mandatory Pre - Installation Steps)

1. Always disconnect the main negative terminal of the battery first, set the ignition switch to OFF, and remove the fuses related to starting. This prevents short - circuits from damaging the electronic control system, wire harness, or magnetic switch.

2. It is strictly prohibited to plug or unplug the Terminal 50 control wire, short - circuit the Terminal 30 constant - power terminal, or use metal tools to contact both Terminal 30 and the starter housing when the power is on.

3. Park the vehicle on a level surface, engage the parking brake, and secure the wheels with chocks. When removing the guard plate/dust cover, avoid scratching components in the engine compartment, and keep tools away from rotating and high - temperature areas.

4. Wear insulating gloves and safety goggles during operation. Prepare an electrical fire extinguisher nearby to prevent hazards caused by sparks from 24V short - circuits.

5. 
   

6. References：
   

7. The following are the authoritative sources and general bases for the Core Precautions for Installing Dongfeng 24V Starter Motor, categorized into three types: core authoritative sources, industry universal standards, and technical experience summaries. These clearly specify the direct bases for key parameters such as torque, wiring, and installation procedures.

8. I. Core Authoritative Sources (Direct Basis for Torque, Wiring, and Procedures)

9. 1. Dongfeng Original Factory Service Manuals (WSM/Service Manual)

10. Key Basis: Torque values including 28–35 N·m for main fixing bolts (37–45 N·m for heavy-duty vehicles), 12–15 N·m for Terminal 30 nuts, 12–15 N·m for shift fork bolts, and 7–10 N·m for wire harness clips, as well as operational principles such as Terminal 30/50 definitions, grounding specifications, disconnecting the battery’s main negative terminal before installation, prohibiting air impact wrench tightening, and step-by-step bolt tightening—all are derived from model-specific original factory service manuals for Dongfeng commercial and passenger vehicles (e.g., Tianlong, Tianjin, Aeolus, etc.).

11. The manuals explicitly specify standards such as the alignment requirement between the drive gear and flywheel ring gear, and the minimum starting voltage of 21V after starter installation.

12. For example, the 37–45 N·m torque specification for main bolts of heavy-duty vehicles and the wiring sequence of Terminal 30/50 are extracted from the step-by-step guidelines in the original factory manuals.

13. 2. Dongfeng After-Sales Technical Training Documents

14. Key Basis: Specifications including magnetic switch terminal definitions for 24V starters (corresponding to Terminal 30/50), shift fork stroke adjustment standards, and the rule of no more than 3 consecutive starts with an interval of ≥ 2 minutes between each start—are sourced from technical training materials provided to Dongfeng authorized dealers. These documents are formulated to standardize maintenance processes and ensure system safety and durability.

15. II. Industry Universal Technical Standards (General Basis for Safety, Lubrication, and Testing)

16. 1. Universal Maintenance Standards for Automotive Electrical Systems

17. Key Basis: Safety requirements such as disconnecting the battery’s negative terminal to prevent short circuits, installing insulating sleeves on Terminal 30 for protection, cleaning grounding contact surfaces, and standardized use of anti-seize grease—are in compliance with universal automotive electrical maintenance safety standards including SAE (Society of Automotive Engineers) standards and GB/T 18411. These requirements are commonly found in industry maintenance guides and technical manuals.

18. 2. Industry Standards for Starter and Starting Systems

19. Key Basis: Technical parameters such as a minimum 70% contact area between the drive gear and flywheel ring gear, a minimum starting voltage of 21V, and the prohibition of greasing gear tooth surfaces—are consistent with installation standards set by leading international starter manufacturers (e.g., Bosch, Delphi).

20. Operational prohibitions including banning air impact wrench usage, avoiding striking the starter housing, and securing wire harnesses to prevent wear—are derived from universal operating guidelines in the automotive parts industry.