Normally located on the bulkhead.
The MFRU houses four relays. There are two connectors, one six pole input control and one eight pole output. The one detailed here is of the older varierty.
The four relays have the following functions:
Main Relay : Controlled by the ECU, this relay switches the +12V supply to many of the sensors, injectors, Idle control, VVC control etc.
Fuel Relay: Conrolled by the ECU, this relay switches +12V to the tank mounted fuel pump via the inertia switch.
Starter Relay:Activated by the crank position on the ignition switch or if fitted, by the starter button. The starter relay supplies +12V to the starter solenoid.
Lambda Relay: Controlled by the ECU, this relay supplies +12V to the heater element of the Oxygen or Lambda sensor for rapid warm up after cold starts.
see MFRU Connector