stockhatch

iTrader: (12)

Hey guys. I am trying to wire a 2GS fuel pump ECU into my SC300 so I can control fuel pump voltage via my Aristo ECU. I can't get it to work correctly, and I think it may be because the SC300 grounds the fuel pump directly to chassis, and the 2GS does not?

Can any of you guys confirm that the 2GS grounds the fuel pump solely via the fuel pump ecu? Its the only thing I can figure is messing me up, as when the GS FPC is plugged in, the pump runs exactly like the 12v mod is done. (Runs full speed when key turned to on, and keeps running for a few seconds after key is turned off.

GS4_Fiend

iTrader: (22)

It doesnt matter where the ground is as long as its a known good ground with 6 inches.

stockhatch

iTrader: (12)

Hmmm...The only reason I suspect what I said is because the wiring diagram I have seems to support my theory. I have never seen a 2GS personally to confirm, but I was looking at the fuel filter replacement thread for the 2GS and it looks like the fuel pump is isolated via the big plastic housing. Are you saying there is another ground for the fuel pump besides the dedicated wire running to the FPC?

GS4_Fiend

iTrader: (22)

Fuel pump ground is the wire with L-W, which shares the same ground with the fuel pump ecu.

99 GS3

iTrader: (14)

The fuel pump is grounded through the pump ecu, but it is also grounded at the hanger assembly with a tab that fits the rim of the tank, and grounds the tank to the pump as well.

stockhatch

iTrader: (12)

Thanks guys. I appreciate it. I think I have a bad FP ecu. I applied 12v to it at B+ and grounded E, and it puts out battery voltage between pins FP and FP-. I dont think it is supposed to do that with no FPC signal.

GS4_Fiend

iTrader: (22)

You're reading battery voltage at FP-? You got an open ground wire or bad Fuel pump ECU.

stockhatch

iTrader: (12)

Actually, if I apply 12v to B+, and ground E, I am reading battery voltage between FP and E, and approx 10v between FP and FP-.

I should not be getting voltage on FP without signal on FPC AFAIK. When I test my SC300 FPECU, I get 0v on FP unless I apply 12v to FPC. Then I get battery voltage on FP as I expect.

I also get 0v on pin DI with the GS part, but I get 12v on DI with my SC part.

I ordered another GS FPECU to test.

GS4_Fiend

iTrader: (22)

Ok. Here's an overview.
Pin 10 (B+) is power (source voltage) when key is on.
The FPC gives the Fuel Pump (FP+) a varying voltage depending on engine load.
FP- then pulls it to ground to complete the circuit, hence fuel pump is running
Pin 5 (E) is the ground for the Fuel Pump ECU.
DI is a transitor that wires to the PCM and the PCM grounds it

To diagnose the problem, I would turn the car on, Pin 10 (B+) should be source voltage.
Pin 7 (FP+) and Pin 6 (FP-) should read source voltage.
Pin 10 (B+) to Pin 5 (ground) should read source voltage
Pin 8 (FPC) is the control wire, PCM gives power to it to turn on fuel pump at different voltages varying on the load.
Pin 9 (DI) is ground, PCM grounds the circuit.

If you are getting 0V when the car is on, that means, PCM is completing the circuit to ground. If you are getting source voltage, it's not completing the circuit it to ground.

stockhatch

iTrader: (12)

I have no clue what's going on here. The new one does the same thing. They both test out exactly the same. I guess I am stuck with this pump running full bore 24/7

stockhatch

iTrader: (12)

For some reason when I supply 12v to B+ and ground E, I get about 9.5v across FP and FP-. This is with no signal at all on FPC. Then if I feed FPC 5v, the voltage between FP and FP- goes up to battery voltage. Both controllers do this, but I dont know why. Is it normal behavior for the GS FPC to supply 9.5v to the pump as soon as the key is turned?

GS4_Fiend

iTrader: (22)

I dont have the service manual but i suggestion checking power and ground where for high resistance or loose connection. Make sure the pins on the connectors are sittin properly.

stockhatch

iTrader: (12)

I'm testing on the bench now, and each fpc has its own pigtail plug. My sc fpecu works closer to expected when I bench test it.

I feed 12v to B+ and ground E. I get 0v across FP and E until I feed fpc with 12v, at which point I get 12v between FP and E.

GS4_Fiend

iTrader: (22)

Ok. I'm getting confused. Let's start all over again, fresh. Tell me what is your goal your trying to achieve?

stockhatch

iTrader: (12)

Sorry. My goal is to use a fuel pump controller to slow my pump down at idle and low load because it is so loud. It is currently getting battery voltage constantly via the 12v mod. My Aristo ECU puts out 3.5-5v on pin fpc, so it won't work with my stock fuel pump ecu. I heard of people using the gs controller since it will supposedly work with the Aristo signal voltages.