No ECU power.. No start

[mo_hish]

1993 240sx s13 (97 ka24de w/ s13 distributor)

Drove the car this morning to the store, parked it... 5 min later came out and the car wouldn't start. Popped the hood, and found the fuse box cover off, and the ignition coil ground was off. Put the cover and ground back on and wouldn't start.

What I know:
CEL won't come on
No spark
Fuel pump wont prime
Relays and fuses are good
ECU only getting 1.4v at power pins (pins 47 & 38.)
When I jumper 3&5 at the EGI relay, the CEL comes on and the ECU gets power (full 12v at power pins) but wont start
When EGI is jumpered, fuel pump will prime when I unplug the distributor
No spark with or w/o EGI relay jumpered
Pin 36 (Ignition) gets 12v with key in on position
Pin 34 (Start signal) gets 10v while cranking
SAFC still turns on
Opened the ECU and everything looks/smells fine


I'm lost. I'm assuming it's a wiring problem and I'm considering getting another harness, but I don't want to get one if it's not even going to help...

[EklipzGSXkid]

Sounds dumb, But did you check the ignition fuse ? It does not have to be under the enginebay, There could also be a fuse in the interior aswell.

Had this happen to two cars in the past month. SEARCHED for 1 week the entire electrical system and every single wire and pinout, Only to find simplefuse.

Had someone else telling me theyhad to tow their car to 4 diff dealers, Get 2 different ecu's, A reprogramedecu and key,And a new harness. Turned outall they needed aswell was just a hidden fuse that was blown. They wasted alot of time, And ALOT of money .


If your CEL is not on And your not getting spark/fuel, Your ECU is not communicating. Check the ignition fuse and every other fuse in / on the car.

[mo_hish]

lol I wish it were that simple. I just went and double checked all the fuses in/on/around/in the vicinity of my car, I even checked my neighbors car.. they're all good.

[Midnight Ryderz]

Check the ECU's main ground wire as well. If that doesnt' help take the ECU out open it up and smell it. If it smells burnt its a bad ecu. I hope this helps

[mo_hish]

Unfortunately, I've already checked both main ECU grounds as well as looking at and smelling the ECU.. everything seemed fine. It's a fairly new chipped and socketed ECU, so I don't think that's the culprit.

I also tried push starting it by the way, and it doesnt start.

[teh DIRT]

Ive seen IGN switches do some crazy ****. Might not be your issue, but work a look. They make BMW's go nuts.

[mo_hish]

Well I checked:

Pin 36 (Ignition) gets 12v with key in on position
Pin 34 (Start signal) gets 10v while cranking

So I'm assuming that rules the ignition switch out.

[JankyS13]

wondering what tune was it?

doubtful check the ignitor and if that seems to be ok for ****s and giggles see what a stock ecu does.

[mo_hish]

It was a tune I messed with for my old setup (N60, 370s, hy35 ~ 10psi), still in there because I havent had time to retune for the STI injectors I'm running now, just pulled fuel on the AFC.

I actually bought a stock ECU a couple weeks ago for a different reason, now I figured I'd try it to rule the ECU out, still waiting for it to come in the mail unfortunately. I'll check the ignitor too, but that wouldnt stop the ECU from getting power or the fuel pump from priming.

[mo_hish]

Anyone?

[mo_hish]

Ok, so I backprobed some stuff and found a few questionables.
I backprobed the EGI relay, and all 3 wires are getting 12v (with the key on) except for the black/white (power to the ECU?) wire. I'm guessing thats why when we jump the 3 & 5 pins, the ECU gets power. I'm actually pretty sure I get spark with them jumped... It's kind of hard to see, but its there.

Also, I backprobed the ECU checking continuity with ground to see if there was a bare wire touching the chassis or something like that. All the ECU and various sensor grounds that go into the ECU are fine. The ones I'm not sure about are:
Pin 113 (SB) - AAC Solenoid
Pin 45 (G/Y) - Ambient Switch > G > B > FICD
Pin 24 (R) - Check Engine Light (MIL)
Pin 36 (B/R) - Ignition Switch

I had my multimeter set to beep if it was a continuous circuit (1 lead on ground, and checking the pins with the other lead)... with these, it didnt beep, but would sound like static, then if I turned the key to the 'on' position, it would immediately go away. I checked the voltage with the key 'on' and all seemed fine.

[240driver39]

clutch interlock relay? Would be an easy thing to check.

[mo_hish]

I'll check that, but why would that stop the ECU from getting power?

[Nick Merrone]

I know for a fact that car was 5 speed swapped, Might not be it. But just to get it off the list..Neutral saftey switch?

[mo_hish]

Car cranks, that switch wouldn't let it crank.

[Nick Merrone]

oh sorry for me not reading LOL.

[mo_hish]

no worries bro, keep the ideas coming!