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 560SECFACTORY OEM SERVICE PROCEDURE
Visual Check (Fuel Leak)
- Remove air cleaner and check for any visible fuel leaks. Remove fuel pump relay from relay board (under hood on fuse panel). Bridge fuel pump relay board terminals No. 7 and 8 with jumper wire until fuel pressure is established.
- Push airflow sensor plate down manually. Uniform resistance should be felt throughout travel (after slight amount of free travel). No binding should be felt when sensor plate is released. If upward movement of sensor plate is slow, feel for resistance from control piston returning against sensor plate lever arm. No binding should be felt.
- Push airflow sensor plate completely down and briefly hold. No fuel should leak past control piston. Slight fuel seepage is acceptable. If no fuel leaks are found, go to next test.
Factory Service Tools
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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.