I'm sure of the connection and purpose of the FPCM, as looking at the pin-outs theres effectively a relay (although it could be a solid state one) that switches a drop down resistor inbetween the pump and earth, which in turn drops the speed of the fuel pump. But what causes the ECU to switch the FPCM on? Is it purely at idle/closed throttle or is there some other strange logic state attached to it? Cheers Rob
Thats the thing, the Fuel Pump Control Module. Theres almost completely no information about its function, most people remove it or force it onto full power. But da' Phatness aint bein' skanked by no pussy yo FPCM ya get me?
actually stands for Fuel Pump Control Modulator and is just used to reduce noise at idle. it controls the ground circuit of the pump, it is controlled by 1 pin on the ecu on a r34 rb25 cant remember r33 from what i can remember should see around 10volts on that signal line when the ecu is telling it to drop the voltage to the pump. the units actually work quite well we have a 500bhp 2.7 rb25 still using one the power fc switches it off as soon as you come off idle but still quite handy when your sat in traffic especially if you have a noisy pump hope that helps
The operation I'm clear on, its the control logic I'm having issues with. If its solidstate I can PWM it to get varying fuel pressure. As I understand it (through looking at other ECUs) the pressure is less about noise and more about getting larger injectors to flow less fuel at low to mid RPM. Although on a car that is supposed to be refined like the Skyline I could see NVH being a factor they'd want to factor in. On the Pin put I have its on Pin 104 which is in the high current cluster which suggests that it is a low resistance solenoid and not a relay - but I could be wide of the mark. When I get my grubby hands on this device I'll scope the inputs and see just what it does.
Yeah sorry dude just read your first post properly pretty sure its not that clever i know the Toyota and Mitsubishi systems are more complex but as soon as they come off idle with the Nissan system you can hear the pump speed up. Thinking about it that might just be Power Fc equipped cars doing that next one i get in with a stock ecu ill have a look for you. scope it good idea
