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.
1986 Mercedes Benz 560SECFACTORY OEM SERVICE PROCEDURE
Cold Start Valve Activation
- With ignition turned off, pull plug on 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 about zero ohms. If not okay, repair interruption. Go to step 3). If okay, test is complete. See Figure .
- With coolant temperature sensor plug disconnected, check voltage between fuel pump relay plug (terminal No. 12) and TF circuit (terminal No. 2) and engine ground. Crank engine (do not start). Voltage at terminal No. 12 should about 10 volts. Voltage at terminal No. 2 should be about 3.5-5.0 volts. If not okay, repair interruption. If okay, replace fuel pump relay. End of test.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.