Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1991 Mercedes Benz 350SDFACTORY OEM SERVICE PROCEDURE
Spark Plugs
SPARK PLUG TYPES
| Application | Bosch | Champion |
|---|---|---|
| 4-Cylinder | N/A | N/A |
| 6-Cylinder | H9DC | S12YC |
| V8 | W8DC | N9YC |
SPARK PLUG SPECIFICATIONS
| Application | Gap: In. (mm) | Torque: Ft. Lbs. (N.m) |
|---|---|---|
| 4-Cylinder | N/A | N/A |
| 6-Cylinder | .031 (0.80) | 15 (20) |
| V8 | .031 (0.80) | 22 (30) |
IGNITION TIMING Degrees - BTDC @ RPM
| Application | Specification |
|---|---|
| 4-Cylinder | Information Not Available |
| 6-Cylinder | 7-11 @ Idle |
| V8 | 3-7 @ Idle |
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.