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.
1987 Mercedes Benz 560SECFACTORY OEM SERVICE PROCEDURE
Cold Start Valve
- With ignition off, disconnect coolant temperature sensor. Unplug Green cable on ignition control module. Crank engine and check voltage at plug of cold start valve. Voltage should be 10 volts for about 9 seconds. If okay, test is complete. If not okay, go to step 2).
- Check wire from cold start valve to fuel pump relay (terminal No. 4) and ground wire to engine for continuity. Resistance should be zero ohms. If not, repair open circuit. Go to step 3). If okay, test is complete. See Fig 1 .
- With coolant temperature sensor disconnected, check voltage between fuel pump relay connector, terminal No. 12 and engine ground (-). Check terminal No. 2 (TF circuit) and engine ground (-). Crank engine (do not start). Voltage at terminal No. 12 should be 10 volts. Voltage at terminal No. 2 should be 3.5-5.0 volts. If not to specification, repair wiring circuits. If okay, replace fuel pump relay. End of 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.