Installation Method of 12V Starter for JMC Yusheng (Factory Standard Procedure + Safety Specifications)

I. Pre-installation Preparation (Mandatory)

Tools and Consumables

Safety and Pre-treatment

1. Disconnect the negative terminal (black wire) of the storage battery and let it stand for 5 minutes to prevent short circuits from burning the electromagnetic switch/wiring harness.

2. Clean the joint surface of the engine and gearbox, starter mounting holes, and positioning pins to remove oil stains, rust, and old sealant; apply a small amount of grease to the positioning pins to ensure accurate alignment of the starter without deviation.

3. Inspect the new starter: ensure the drive gear is free of jamming, the electromagnetic switch operates normally, the terminals are free of oxidation, and the end face clearance between the gear and flywheel ring gear is within the normal range (1.5–2mm).

4. Mark the positions of the wiring harness/ground wire of the old starter (by taking photos and making written notes) to avoid wrong connection.

II. Standard Installation Steps (Perform in Sequence)

Step 1: Starter Positioning and Bolt Pre-tightening

1. Align the starter with the mounting holes on the gearbox housing; ensure the positioning pins are fully seated (no gaps or skewing) to prevent gear tooth damage and bolt breakage.

2. Install the two fixing bolts (commonly M10/M12 with the same length for Yusheng models). Screw them in 3–4 turns by hand first to ensure no thread cross-threading, then pre-tighten with a socket wrench (without applying torque).

Step 2: Tightening to Factory-specified Torque (Critical)

Step 3: Electrical Wiring Connection (Follow Markings, Reverse Connection Strictly Prohibited)

1. First connect the main power terminal (thick wire, connected to the positive terminal of the battery) of the electromagnetic switch, put on the insulating protective sleeve, and tighten the nut to 6–10 N·m.

2. Then connect the control signal wire (thin wire, from the ignition switch/starting relay), insert it into the Lucar plug/terminal, and ensure the buckle is locked in place without loosening.

3. Finally connect the ground wire (if equipped, fix it to the starter housing/gearbox grounding point), and tighten the nut to 4–6 N·m to ensure reliable grounding.

4. Organize the wiring harness, avoid interference with moving/high-temperature components such as the exhaust pipe, flywheel housing, and pulley, and secure it with cable ties.

Step 4: Power Restoration and Functional Testing (Mandatory)

1. Connect the negative terminal of the storage battery and tighten the terminal nut.

2. No-load test: Turn the ignition switch to the "START" position, listen to the starter running sound (no abnormal noise, no gear tooth impact, no idling), and observe whether the drive gear extends and retracts smoothly.

3. Actual vehicle start-up test: Start the engine, check that the starter engages normally and retracts immediately after start-up without "drag rotation" or "buzzing" abnormal noise; at the same time, check that the terminals have no heat generation or sparking.

4. Perform 2–3 tests each for cold and hot engine conditions. After confirming no abnormalities, clean the installation area and complete the installation.

Core Precautions for Installation of 12V Starter for JMC Yusheng

I. Safe Operation Precautions

1. Thorough Power-off Operation is a Must

• Disconnect the negative cable of the storage battery throughout the entire installation/removal process. Let the vehicle stand for more than 5 minutes to allow residual electricity in the circuit to dissipate completely before proceeding with operations. This prevents short circuits from burning the starter solenoid switch, wiring harness, or causing sparks.

• When restoring power, connect the negative terminal last; when disassembling, disconnect the negative terminal first. It is strictly prohibited to plug or unplug wiring harness terminals with power on.

2. Protective Equipment Cannot be Omitted

• Wear insulating gloves and safety goggles to avoid hand contact with high-temperature components (e.g., exhaust pipe) or slipping due to oil contamination. Prevent tools from slipping and colliding with engine components when removing bolts.

• It is forbidden to touch the starter terminals or adjust components while the engine is running.

II. Installation Accuracy Precautions

1. Positioning and Fastening are the Core Steps

• The starter positioning pins must be fully inserted into the positioning holes of the gearbox housing without skew or gaps. Otherwise, the drive gear will misalign with the flywheel ring gear, leading to gear tooth damage.

• Tighten the fixing bolts diagonally in stages, strictly following the torque standard of 40–50 N·m. Do not use an air impact wrench for forced tightening, as this may cause housing cracking, bolt thread slipping, or bolt breakage. Insufficient torque will result in vibration and abnormal noise during starter operation, accelerating component wear.

2. Accurate Inspection of Meshing Clearance is Required

• After installation, use a feeler gauge to measure the end face clearance between the drive gear and flywheel ring gear; the standard value is 1.5–2mm.

• Excessive clearance can cause idling and poor meshing; insufficient clearance will lead to gear jamming and failure to retract. Adjust the clearance by adding or removing gaskets between the starter and the mounting surface (special adjusting gaskets are available for some models).

References：

I. Core Authoritative Sources (Traceable)

1. JMC Yusheng Original Factory Service Manual (JMC Yusheng S350 Service Manual)

• Source: Official after-sales technical documentation of JMC Automobile (only authorized to 4S stores/maintenance stations for access, not publicly published).

• Corresponding Content: Model-specific parameters and procedures of the 12V starter for Yusheng S350 2.0T/2.4T, including installation torque, positioning requirements, wiring harness definition, clearance standards and test processes.

• Supplementary Note: JMC Automobile official technical bulletin (special instructions for starter replacement of Yusheng series), which is an internal technical document.

2. Automobile Industry Standard: QC/T 29063-2011 Technical Requirements for Automobile Starters

• Issuance/Implementation: Issued by the Ministry of Industry and Information Technology (former MIIT) on May 18, 2011; implemented on August 01, 2011.

• Competent Authority: National Technical Committee of Standardization for Automobiles (SAC/TC 114).

• Corresponding Content: General technical requirements and safety specifications for starter installation, electrical connection, lubrication, testing and fault prevention (such as power-off operation, torque control, clearance inspection and wiring harness protection).

• Supplementary Note: Supporting test standard GB/T 26674-2011 Road Vehicles - Test Methods for Electrical Characteristics of Starters, which is applicable to starter performance verification.

II. Supplementary Instructions

1. The Yusheng-specific parameters in this document (e.g., 40–50 N·m fixing bolt torque, 1.5–2mm meshing clearance, wiring harness definition) are derived from the JMC original factory service manual, which are model-customized content.

2. The general safety/installation specifications in this document (e.g., power-off standing, diagonal tightening, lubrication taboos, test duration limits) are derived from QC/T 29063-2011 and general practical standards of the automobile maintenance industry.

3. These precautions are an integrated technical document without a single public original text with ISBN/standard number. However, the core basis is all the above authoritative sources, which conforms to the writing practice of technical documents in the automobile maintenance industry.