Derekcat

iTrader: (8)

Hey guys,
Continuation of this issue: https://www.rx7club.com/power-fc-for...arted-1055618/

Quickly:
'91 A package, swapped to a turbo drivetrain, all NA wiring harnesses, PowerFC with the Banzai Racing wiring adapter kit, FD fuel pump, fuel pump resistor/relay bypassed...

The car will start up if the fuel pump check connector is jumpered, but otherwise the fuel pressure drops immediately after startup. I have a gauge in line to watch it.

I don't know if it's related, but the security light will flash once when the key is switched to OFF, otherwise it never illuminates.

No, I can't test with the N370 ECU/pressure sensor/AFM I have, I don't have the intake tube to attach the AFM.. >_<
The PFC is used, and bought from a very reputable friend, and it was RMA'ed to Apex'i at some point.

The engine has good compression, starts up about as easily as any rebuild that's run for half an hour will, using a standard Banzai map for S5 turbo, with the secondary injector size field changed to 1000 (New ID1000 secondaries, sonic cleaned stock JDM primaries).

I've searched the crud out of this and haven't found anything helpful - everything I've found was stockish cars that stopped working and magically fixed themselves or had an AFM connection problem. (The resistor bypass was the only other helpful troubleshooting suggestion..)

Thanks!

satch

iTrader: (1)

What ECU are you using? It states you are using the Power FC but is that an add on to your ECU or a complete stand alone?

Derekcat

iTrader: (8)

The PowerFC is a standalone designed for FDs.
So I'm running an ECU wiring harness adapter from Banzai, a Triumph air temp sensor (same voltage range as FD, but faster reacting), a GM 3-bar air pressure sensor (with Banzai adapter, and setting in the PowerFC to use it), and an S5 JDM TPS (AFAIK, compatible with the FD's - it seems to read correctly).

satch

iTrader: (1)

So, the car operates properly only if the fuel check connector jumper is in place. Correct?

Derekcat

iTrader: (8)

Yep!

Watching the fuel pressure gauge, it builds up while cranking and then drops as soon as it starts running the pressure drops. With the connector jumpered, it runs indefinitely.

satch

iTrader: (1)

The stock ECU on an S5 would send a signal to the Circuit Opening Relay which governs power to the fuel pump when the engine has started, and w/o it the engine would die (the jumpering provides the relay w/what it needs to keep the engine running). Thus it should be your focal point.

GeenIdee

I have also a power fc meant to be for a 93 FD with the banzai harness and had no problems.

Fist thing that came up in my mind was a faulty fuel pump resistor relay, in the engine bay behind the right headlamp. looks like this

I am not sure, but I could imagine that the risitor inside is broken.


What you can do to test this, is to bypass the resistor relay.

Disconnect the resistor relay, take the connector that sits on the car, connect position E with position F and A with position B like shown in the picture below.




Before I changed te complete fuel pump setup on my car, I bypassed this to get max voltage always. And not "when you need it". To make sure the 23 year old wiring wouldn't give a voltage drop, I only used this to power a relay that I mounted near the fuel pump. But I must say that I also had the battery relocated to the back of the car.

This is the diagram I made back then. This is how I contect the fuel pump.



If this is not the problem, find the circuit opening relay (i belive it sits under the dash, drivers side), and do some measurements there.