Electrical Relays

The main relay activates the ECU, injector circuit and starting circuit when ignition is switched to start mode. The fuel pump relay activates the fuel pump during the start mode and is then controlled by air flow during operating mode. Some models incorporate all relays within a single relay set or dual relay. The cold start system is also activated through the relay set.

Relay set is located in following positions:

• 528e and 533i, bracket above left wheel well.
• 633CSi, behind coolant reservoir.
• 733i, right side of firewall.