Fuel Opening Circuit Relay

[Matt]

The fuel opening circuit relay ( FOC) effectively is 2 relays built into one. Its sole purpose is to control your fuel pump and have some intelligence built in so in the event of an accident, fuel isn't going to continually be pumped whilst the engine isn't running etc..

In the corollas, to get to the FOC you will have to remove the centre console and gain access to the ECU. In the ae82/92's there is a bracket on the ecu which the FOC slides onto. In the ae101/ae111's they are located on the metal support that the centre console bolts into.

In the zze and later models, the ECU controls the fuel pump directly as they are returnless setups.

Here is a pic of the FOC





For those wondering what a relay is

The FOC can be activated by 2 methods.

Earthed

The FC pinout on your ECU in case of a map sensored car or the air flow meter for AFM cars, will provide an earth and activate power to the output wire providing all things are in order and the car is running.

12v Trigger Input

The starter / cranking wire will also trip the relay and activate power to the output wire.

If you don't have a FOC you can wire 2 relays in to operate your fuel pump.

Now into the actual pinouts.

Switched Earth (ecu/afm) - Green / Red
Switched 12v (starter) - Black / White
Output (Fuel Pump) - Blue / black
High Amp Input (Output of EFI relay) - Black / Red
Non Switched Earth - White / Black



It is also worth noting the output wire to the Fuel pump is also spliced into the Diagnostic Box within the engine bay. That is why you apply 12v to the fuel pump in the Diag box the fuel pump turns on.

*** EDIT ADD WIRING DIAGRAM ****

[Matt]

For those wondering how you wire the relays back to back if you don't have a FOC relay.

Relay 1

Pin 30 to battery source
Pin 85 Straight to an earth
Pin 86 to Starter Relay
Pin 87 To Fuel Pump

Relay 2

Pin 30 straight to battery source
Pin 85 to FP pin on the ECU
Pin 86 Splice into pin 30
Pin 87 To the Fuel Pump

You can use the same power source for both relays. You can also use 1 output wire to the fuel pump joined to each relay on pin 87