* Damaged Wiring Harness: This is the most common culprit. Welding generates intense heat and stray electrical currents. Even if the welding wasn't directly on the harness, heat can melt insulation, creating shorts or breaks in wires. This is particularly true near the engine bay where the harness is densely packed. Check for any burnt or melted wires, especially around the battery, starter, alternator, and ignition system.
* Ground Issues: Welding can disrupt ground connections. A poor ground can prevent the starter motor from receiving enough current to crank the engine. Inspect all ground straps and connections for corrosion or damage.
* Computer/ECU Issues: While less likely, stray electrical currents during welding could have damaged the engine control unit (ECU) or other electronic control modules. This is more of a possibility if the welding was near the engine control system. A diagnostic scan might reveal codes pointing to this.
* Battery Problems: The welding process may have stressed the battery, leading to a low charge or damage to the internal components. Check the battery voltage and consider a battery test.
* Starter Motor Damage: While less likely, the intense magnetic fields from welding could have, in theory, damaged the starter motor's windings or other components if it was extremely close. This is less probable than wiring damage.
* Alternator Issues: Similar to the starter motor, though less likely.
What to do:
1. Visual Inspection: Carefully examine all wiring, connections, and ground straps near the welding area. Look for any signs of burning, melting, or damage.
2. Battery Check: Test the battery voltage. A low voltage indicates a charging problem or a weak battery.
3. Check Fuses and Relays: Inspect all fuses and relays, particularly those related to the starting system.
4. Ground Connections: Clean and tighten all ground connections you can find, especially those connecting the engine block, chassis, and battery.
5. Professional Diagnosis: If you're not comfortable checking the electrical system yourself, take it to a qualified mechanic or auto electrician. They have the tools (like a multimeter and diagnostic scanner) to pinpoint the problem accurately.
It's crucial to be methodical in your troubleshooting. Don't jump to conclusions and replace parts randomly. A systematic approach, starting with a visual inspection and basic checks, is the most efficient way to resolve the starting issue.
