* Fuel pump relay itself: This might be a dedicated relay, or its function might be integrated into a larger control module. Its location varies depending on the specific build and options of the car. You won't find a label clearly saying "Fuel Pump Relay".
* Main relay: The fuel pump might be controlled indirectly through a main relay.
* Engine Control Unit (ECU): The ECU plays a crucial role in controlling the fuel pump based on various sensors and conditions. A faulty ECU can prevent the pump from working even if all the relays are good.
To find the relevant component(s):
1. Consult your owner's manual: This is the best place to start. It may have a fuse/relay diagram.
2. Mercedes-Benz wiring diagrams: These are available online (often for a fee) through various automotive parts websites or specialized Mercedes-Benz resources. They provide the most accurate information. Search for "1989 Mercedes 300SEL wiring diagram".
3. Visual inspection: Carefully examine your fuse box and relays. Some might have faint markings indicating their function. However, this is unreliable without the correct diagrams.
4. Professional help: A qualified mechanic specializing in Mercedes-Benz vehicles will have the expertise and diagrams to quickly identify the relevant component(s) and diagnose any issues.
Warning: Incorrectly working with relays and electrical systems can damage your car. If you're not comfortable with automotive electrical work, seek professional help.
