Introduction
This page provides information in regards to Toyota Fuel Pump Control ECU control and how the engine ECU FPC pin can be used to trigger a Circuit Opening Relay (COR) for fuel pump control.
Triggering a COR from the FPC pin can be useful when transplanting an engine from a vehicle that normally has a Fuel Pump Control ECU (i.e. JZZ3x, JZA80, JZS14x, etc) into a vehicle that is fitted with a COR.
Please see the following page for more detail in regards to CORs: Circuit Opening Relay.
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Fuel Pump Control ECU System
The purpose of the fuel pump control system is to reduced the fuel pump speed at low load conditions to make the fuel pump quieter and also improve fuel pump longevity.
This control is achieved by the engine ECU having a pin that is used to signal the desired fuel pump speed to a dedicated standalone Fuel Pump Control ECU.
In this system the Fuel Pump Control ECU receives a signal from the engine ECU and sets the voltage that is outputted to the fuel pump accordingly. This voltage determines how fast the fuel pump operates, a higher fuel pump voltage results in a higher fuel pump speed and vice versa.
Literature suggest that "two speed" and "three speed" fuel pump control systems exist. In the two speed system, at 'low' speed the Fuel Pump Control ECU outputs ~9V to the fuel pump and when in 'high' speed mode battery voltage is outputted to the fuel pump. In the three speed systems the output voltage to the fuel pump is ~8.5V, ~10V and battery voltage.
Engine ECU FPC Output Pin Function
The engine ECU pin labelled FPC is the pin that is used to signal the desired fuel pump speed to the Fuel Pump Control ECU.
Engine ECU FPC & DI Pin Operation
The engine ECU outputs a 0V to 5V Pulse Width Modulated (PWM) signal on the FPC pin which is connected to the Fuel Pump Control ECU to control the speed of the fuel pump.
The Fuel Pump Control ECU also has an output to the engine ECU that indicates that the Fuel Pump Control ECU is healthy. The output from the Fuel Pump Control ECU connects to the engine ECU pin labelled DI. The Fuel Pump Control ECU connects the engine ECU DI pin to battery voltage when the Fuel Pump Control ECU is healthy.
It is worth noting that at least on some engine ECUs that if the engine ECU DI pin is not connected to battery voltage then the engine ECU will stop the PWM output on the engine ECU FPC pin which will then signal to the Fuel Pump Control ECU to turn the fuel pump off.
Fuel Pump Control ECU System Wiring
Triggering a COR from Engine ECU FPC Output Pin
FPC to COR Trigger Circuit Description
The below circuit takes the PWM waveform from the engine ECU FPC pin and uses an RC circuit to generate a voltage that is used to turn on a FET to trigger a relay (usually the COR or fuel pump relay) and turn the fuel pump on.
If the PWM signal is not present the FET will be off and the relay will not be energised and the fuel pump will be off.
FPC to COR Trigger Circuit Schematic
FPC to COR Trigger Circuit Jaycar Part Numbers
Parts to assemble the circuit can be purchased from Jaycar. Part numbers are accurate as of 13/09/2012.
Veroboard: http://www.jaycar.com.au/productView.asp?ID=HP9540
R1: 1kΩ Resistor: http://www.jaycar.com.au/productView.asp?ID=RR0572
C1: 1uF Capacitor: http://www.jaycar.com.au/productView.asp?ID=RZ6627
R2: 1MΩ Resistor: http://www.jaycar.com.au/productView.asp?ID=RR0644
D1, D2: 18V Zener Diode: http://www.jaycar.com.au/productView.asp?ID=ZR1418
Q1: 2N7000 MOSFET Transistor: http://www.jaycar.com.au/productView.asp?ID=ZT2400
References
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