Tyler [S5 FC]

So I have an 89 GXL, to which I've done a TII swap. I have two ECU's; N351 N/A, and N370 Rtek 1.5. The car runs on the the N/A ECU, but obviously won't boost. Then when I plug in the Turbo ECU, it cranks over for a second and dies. The code is 3k, which is one of the relays, sorry, don't have the sheet in front of me. But says the voltage should be at 0 with ignition off, 12v with ignition on, and 2v or below at idle. Mine's at 12v at idle. So I'm about to call Rtek, but thought i'd do some more research, and searched their forum. To where I saw a similar issue, and it was resolved by "resetting the ecu." How do you do this?

satch

iTrader: (1)

Disconnect the negative battery terminal for about 15 minutes or so then reconnect the cable.

Tyler [S5 FC]

Damnit, Yeah, i did that, so i guess it's not that. I was told by a couple people to disconnect the MAF, so I'm gonna try that once I get off work.

satch

iTrader: (1)

But did you leave the battery disconnected long enough. It's not a quick disconnect quick reconnect type of thing.

EDIT:

When you say the code is "3K" are you referring to the pin on the ECU or something entirely different?

RotaryRocket88

iTrader: (7)

What is the actual code being given? 3K isn't a code number. http://www.johnr.com/cpucodes.html

I'm guessing by 3K you mean ECU pin 3K, which is the circuit opening relay. Pg. F2-79 does list it as ign. off: 0v, ign. on: 12v, idle: 2v. If you then take a look at Pg. Z-44 of the wiring diagrams, you can see the circuit opening relay has its coil energized via pin 3K. So the ECU switches the relay on when there's a start signal or the AFM says the engine is running. The circuit opening relay then energizes the fuel pump relay, which powers the fuel pump. It seems to me that seeing 12v on 3K at idle would be normal, but there are a couple of resistors in the diagram which may drop voltage at idle. Fuel pump voltage is definitely supposed to drop at idle to about 9v.

Just for the heck of it, try jumping the fuel pump test connector. You'll bypass the ECU and energize the circuit opening relay permanently. See if anything changes. You could also test voltage at the fuel pump to get a better idea of what's going on.

satch

iTrader: (1)

As I understand it the Brown wire from the ECU, pin 3K, has to have a ground signal for the car to run. To start the car the Circuit Opening relay relies on a different coil which has a "constant" ground as opposed to the "other" coil which has a ground only until the car has started and is required to keep the car running.

RotaryRocket88

iTrader: (7)

On second glance, I was looking at the wrong ECU-connected wire for the circuit opening relay. The B/R one is pin 1C (the one I was looking at), so you're right, the BR wire is 3K. One coil for each kind of ECU signal. Makes more sense now, hah.

So 3K is switched ground from the ECU (AFM signal), and there is a resistor there that'll drop voltage when the fuel pump becomes active.

1C is switched power from the ECU (start signal).

Tyler [S5 FC]

Thank you guys! Works perfectly, and feels awesome, first time I've ever boosted in my own car was five minutes ago. I'm ecstatic!