I hate wiring, Help me 4x4 my IX! No Spark, FML

[accident]

the OBC doesnt stop spark, it cuts the fuel pump. jake sorry i didnt get back to you this weekend, shit got hectic. let me know when you're free again and i'll try to make it

[DaveSmed]

the OBC doesnt stop spark, it cuts the fuel pump. jake sorry i didnt get back to you this weekend, shit got hectic. let me know when you're free again and i'll try to make it

This is incorrect.

The OBC interrupts power to the coil and pin 27 of the DME for MY88 E30s. Earlier cars it just interrupts pin 27. No cars disable the fuel pump.


With that said, your car being an 88 pin 27 and the coil are on the same circuit.

That single honk.... Does it sound like the normal E30 horn or higher pitched like a honda for example? Is there any modified wiring going into the black box?

[DaveSmed]

Hmm, that black connector with two wires looks like C136, There should be a single wire connector floating around somewhere, C131.... What the heck is that white one?

[JakeP]

DaveSmed: I guess the horn sounds like a stock E30, but this is my first BMW...
I haven't found an alarm if that's what you're hinting at. Wiring going into the black box is unmodified and switching a working black box doesn't change anything. Found some wires eaten by a rat, spliced them back together and no difference.

Here's the current symptoms in the most logical order:
No start
No spark
No power to coil
No power to pin #27
OBC doesn't light up


Randoms:
Horn fuse blows if I try to use it
Injectors wont click when I ground pins 15/16 on the DME connector
Horn honks when I turn the key to ON position and again when the key goes from start to ON position


Good things:
Have fuel at fuel pressure regulator outlet
have power/ground pretty much everywhere else it's required
Motor turns over, just won't fire up.

[JakeP]

Obc turns on, but dim. Tried a junkyard obc, its bright, but neither of them start the car or give power to pin 27.

[DaveSmed]

DaveSmed: I guess the horn sounds like a stock E30, but this is my first BMW...
I haven't found an alarm if that's what you're hinting at.

Shoot, so much for the easy idea. :D

Wiring going into the black box is unmodified and switching a working black box doesn't change anything.

The OBC is screwy for some reason. That box is supposed to pass through in the event of a dead OBC.

Found some wires eaten by a rat, spliced them back together and no difference.

Hell that could cause anything. Why do they eat wires???

Here's the current symptoms in the most logical order:
No start
No spark
No power to coil
No power to pin #27
OBC doesn't light up

First four are due to pin 27. Last one is interesting. The lightbulb could just be burned out. Shine a flashlight directly at the display, see if it says ----UHR (ok) or ----CODE (not ok)

Randoms:
Horn fuse blows if I try to use it

Hell that could be anything, BUT! it also tells me its not the normal horn beeping at you, which means its the OBC horn. Which is controlled through the same black box. Interesting.

Injectors wont click when I ground pins 15/16 on the DME connector

Expected. The DME is not energizing the main relay.

Horn honks when I turn the key to ON position and again when the key goes from start to ON position

That is friggin weird. It is NOT supposed to do that, in any mode. What the hell is that thing up to?

Good things:
Have fuel at fuel pressure regulator outlet

Que? As in fuel pump turning on? That's not supposed to happen w/o the main relay OR DME.

have power/ground pretty much everywhere else it's required
Motor turns over, just won't fire up.

Man if that's not a frustrating situation....

Hopefully we can figure it out!

[DaveSmed]

Still beep with the new OBC?

[DaveSmed]

Here's the diagram of everything that black box is up to. Try unplugging C1

The arrow going off to "Injection Electronics" is your Ignition coil.

[Hellabad]

I would run a (fused) jumper from + on the coil to the + battery jump stud, and turn the key.

This will back 12 v all the way down the line and light up lots of things, hopefully even the coil.

I like this idea because it takes about 1 minute and gets lots of scenarios out of the way.

[JakeP]

Ok, to clarify a couple things (cause I suck at BMW's): I got fuel to the rail by jumping the relay. It won't pump by itself.

Both OBC's turn on with the key in the on position and say ----UHR, but one of them is just dim.

Horn honks with both OBC's.

How do I read that chart? I see C1 near the OBC control module, but what wires are they, or what does the plug look like?

Hellabad: hmmmmm, that sounds really tempting. I would be afraid that it would screw something up though.

[Danny]

When you turn the key to on, is there a check engine light?

[JakeP]

I don't believe so. Only the CHECK light. (flashing)

[Danny]

Yes its bad. It means something is fucked up with the grounds.

For me it meant replacing the 3 realys.

[JakeP]

I've tried swapping the 3 relays near the overflow reservoir. :(

[Danny]

Welp, that's all the help i have for you.