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.
1990 Mercedes Benz 350SDFACTORY OEM SERVICE PROCEDURE
Section 1 (Engine Controls - Basic Testing)
WARNING: This page does not describe the selected car, but rather 19 other vehicles, including the 1992 Mercedes-Benz 500E, 1992 Mercedes-Benz 400E, 1992 Mercedes-Benz 300TE, 1992 Mercedes-Benz 300E, and 1992 Mercedes-Benz 300D. However, it is still accessible from the selected car via links, so may be relevant.
- Introduction
- Preliminary Inspection & Adjustments
- Fuel Delivery & System Pressures - Gasoline
- * Please Read First *
- Visual Check (Fuel Leak)
- System Pressure Test
- Lower Chamber Pressure Test
- Residual Pressure & Internal Leak Testing
- Fuel Pump Delivery Volume To Pressure Regulator
- Fuel Pump Pressure
- Fuel Distributor Delivery Volume
- Testing Fuel Pump Relay (420SEL & 560 Series)
- Mas-Engine Systems Control Unit
- Fuel Delivery & System Pressures - Diesel
- Fuel/Water Separator Filter
- EZL Electronic Ignition Checks
- Idle Speed & Ignition Timing
- Summary
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.