Possible bad ECU?

[Booztd 3]

Guys

I'm doing a swap for a local dude on his S13 and I'm not getting any power to the ECU.

I am familiar enough with the nissan ECU's to know that there is a constant power wire (PIN 4 - Red/Black strip) that should get constant power. When the ignition it turned on, it will send a signal to the ECCS (ECU/MAIN) relay to power it on, which then opens up power to the ECU allowing it to turn on.

Currently, that is not happening with the SR20 ECU i was supplied.

I took the ECU out of the car and gave the ECU power wire (PIN 47 i believe - Black/White Stripe) power and grounded the ECU on my bench and it turned on, so I know the ECU does have the ability to turn on.

I noticed that when the ECU is in the car and I turn the ignition is on, Pin 4 gets constant power, no matter if the ignition is on OR off.

I swapped the KA ecu back into the car, and everything operates normally. The fuel pump turns on, the ecu turns on, etc. I also monitored the behavior of Pin 4 and it gets constant voltage when the car is off, and as soon as the ignition is turned on, the power to that wire disappears.

I am leading towards something being bad in the ECU, considering with the KA ECU in the car, it acts normally as it should.

Thoughts?!?!

[PyR0NiAk]

If the ECU turns on on a bench, but you can't mimick it in the car, and you know you're losing power to a certain wire, you've got something wrong with that wire.

[Booztd 3]

If the ECU turns on on a bench, but you can't mimick it in the car, and you know you're losing power to a certain wire, you've got something wrong with that wire.

The KA ECU turns on inside the car and the fuel pump primes and everything. Thats a good indicator the wires are correct, considering the power scheme is the same in regards to the ECU Plug and the KA & SR ECU's

[PyR0NiAk]

If the ECU turns on on a bench, but you can't mimick it in the car, and you know you're losing power to a certain wire, you've got something wrong with that wire.

The KA ECU turns on inside the car and the fuel pump primes and everything. Thats a good indicator the wires are correct, considering the power scheme is the same in regards to the ECU Plug and the KA & SR ECU's

I'm not disagreeing with you, but the part where you said:

I took the ECU out of the car and gave the ECU power wire (PIN 47 i believe - Black/White Stripe) power and grounded the ECU on my bench and it turned on, so I know the ECU does have the ability to turn on.

says that when the ECU is in the car, it's not getting power or it's not grounding.


You have 2 statements that seem contradicting. (At least they do the way I'm reading them.)

[Booztd 3]

The reason the ECU isnt getting power is because the ECCS relay isnt coming on.....

My theory on why the ECCS relay isnt coming on, is derived from a malfunctioning ECU. This is because the ECU triggers the ECCS relay to open up, and actually power the ECU

[PyR0NiAk]

I see. Well, since you're doing a swap for a guy, I'm going to guess that you know a decent amount of people in the local import scene. I recommend trying to find someone else that has an SR, and trying to see if their ECU will turn on inside the car.

[Booztd 3]

If the ECU turns on on a bench, but you can't mimick it in the car, and you know you're losing power to a certain wire, you've got something wrong with that wire.

The KA ECU turns on inside the car and the fuel pump primes and everything. Thats a good indicator the wires are correct, considering the power scheme is the same in regards to the ECU Plug and the KA & SR ECU's

Was lucky enough to find someone in town with an S13 SR swapped car tonight and they allowed me to swap in their "62" ECU for some testing. The fuel pump primed, etc. I cranked the car over for a little while and it did not start, however, it tells me theres something goofy going on with that initially supplied ECU

[PyR0NiAk]

Exactly what I was suggesting. Glad you figured out the ecu issue.

[Booztd 3]

Got the replacement ECU in today.....

Put a fresh set of plugs in it and it fired right up.....now on to the s*** part.

This kid got the engine from a local dude who said everything was good.....now wont return his phone calls/texts...

After it fired up it started knocking like a bandit.....sounds like the bottom end at least is trashed....I feel bad for the kid

[PyR0NiAk]

This type of s*** happens a lot... He planning on rebuilding himself, or paying you, or some shop to do it?

[Booztd 3]

We're weighing some options...

I told him probably the quick/easy way would be to just look around local at some trusted guys and try to find something thats ready to swap in.

Now that we've got the hard part done (wiring, IC pipe routing, coolant hoses, etc) it shouldnt be too bad to just pull the engine, transfer some parts over, and throw it back in.

[Booztd 3]

Well, more interesting events tonight......The kid wanted to get the car home but was somewhat afraid to drive it.

I offered to try and limp the car home till he could decide what to do......

I made it 3 blocks from my house and the #2 rod shot out the drivers side of the block.......ouch!

[PyR0NiAk]

Well, I guess that solves the problem of whether or not to rebuild THAT motor... s*** luck, btw.

[zachattack_5491]

I think I would seriously consider donating some money to that guy. I don't know what I'd do if I got conned on my motor. Poor dude.