m50 power wiring, need assistance

[LooN]

Having some trouble with M50 harness power wires. Best to explain with pics:



These wires come out of the main engine harness at the firewall.
WIRE A: I believe this is supposed to connect to the power distribution block. I did a continuity test and it registers with pin #26 on the DME plug.
WIRE B: I believe this is the harness ground that's supposed to connect to the strut tower. Continuity test registers it with about a zillion pins on the DME plug, so I'm pretty sure it's the harness ground.

I connected wire A to the power distribution block and grounded wire B to the strut tower. When I turn the key halfway, all the electronics come on and work--interior lights, windows, gauge cluster, on board computer, blinkers, headlights, hell even the seat warmers. When I try to START the car, however, there's just a loud snap and EVERYTHING goes out for about 5 minutes, after which the electrical system seems to work again. I've only done it twice, once with both wire A and wire B grounded and once with wire A connected to the power distribution block.

As far as I can tell, everything else is wired correctly--the big red wire that goes across the firewall is connected to the power distribution block and the two ends are connected to the starter and the fusebox. Another big red wire connects the starter to the alternator.

I think my problem may have something to do with this thing:


As far as I can tell, the car had an aftermarket Alpine alarm installed in it at some point--the guy who had it before me, for whatever reason, cut it all out. I have the entire system and all the cut wires, and I can see the cut ends behind the passenger side dash. I think this is part of it. This wire comes out of the chassis on the passenger side and it has some body harenss wires crimped into it, as well as these fuses. I don't know if it should be grounded or connected to the power distribution block. The big black horn thing in the picture--I think that's the aftermarket alarm horn. Can anyone confirm any of this or tell me either way what it is?

Help me start my car! I don't want to fry this harness and i nearly shit my pants every time I even THINK about turning the key.

Also, slightly related, does this groundwire go anywhere? THis is the only one I've seen as long as I've been working on the car but I have a feeling it might be important:


Thanks in advance!

LooN

[Rocla]

Try to track down those wires, constant +12 should turn red somewhere and ground should turn to brown.

That braided wire is grounding for coils. Remove coil cover and see if there is another of those wires, one wire should go to coil 1 mounting bolt and another wire to coil 4,5 or 6 monuntig bolt.

[LooN]

is the braided wire is for coils? i dont think it is because it comes out of the body harness as opposed to the engine harness..i have an E36 if that makes any difference

what else could be causing the car to short out when i try to start it? im stumped here

[tonytony]

did you check the starter? maybe you have the two small wires switched

[browntown]

I might be retarded and can't go look, but I can swear I have that small of a ground strap between the hood and chasis.

[tonytony]

I might be retarded and can't go look, but I can swear I have that small of a ground strap between the hood and chasis.

that looks like it to me, i was just messing with it last night while trying to align my hood.

[LooN]

did you check the starter? maybe you have the two small wires switched

I was thinking the same thing, i'm about 80% sure i connected them right but I didn't think that having them switched would cause the entire electrical system to short. I'll check them tonight when I get off work...ugg..not looking forward to taking that manifold off again

[The Fast One!]

what starter are you using,

I know using an e46 one you can't even switch the two wires around so there hooked up wrong.

those two wires though if


A: goes to straight power for the fuse box.

B: yes that is a ground thats what will ground your ECU.


as far as the short, are you popping fuses? whats shorting.

[Rev Engineer]

I think you're shorting something out at the starter. When you move the key to the "start" position, the primary thing that happens is +12 getting applied to the black/yellow wire. Maybe the black/yellow wire is connected to a ground point on the starter? Or, maybe the starter is bad and shorting it's +12 wire to ground via the solenoid? Not sure what's going on, but I suggest you take the manifold off and recheck the starter very closely. The manifold was the last thing I put on AFTER I made sure the starter worked via the ignition key. I think the key here is to remember the difference between the on and start key positions. Since everything seems to work fine in the “on” position, my bet is with the black/yellow wire and/or the starter.

I agree with everyone else that B goes to ground and A goes to the power block. The braided wire is probably from the chassis to hood. The purpose of this wire is to ground the hood to aid in radio reception and prevent ignition noise from radiating out of the car.

FYI – I don’t think the mega-buck tree house connector always solves these electrical problems. Anyone can mis-wire the starter or not connect the power distribution block properly. On the plus side, they do have tech support you can use. But our collective knowledge on this forum might be greater than what Treehouse can provide. YMMV

[LooN]

I am so stumped. I have checked, rechecked, and rechecked again all my wiring and everything is as it should be. Starter wires are all good. Alternator wires are good. Main power to distribution box is good.

When I try to start the car I can actually feel a kick, like a jolt of electricity go through the chassis...it kind of feels like someone just ran full speed into the side of the car. The lights all go out for a half second or so, then it recovers and all the electronics work again--they are all on when the key is in the "on" position.

I'm pretty sure I have a positive battery lead connected to a ground SOMEWHERE because when I try to start it, it feels like the power from the battery is just discharging into the chassis. I dont think the starter is bad because the engine would turn over all day with the old harness. I haven't found any fuses that are blown.

Where could I possibly be grounding the ignition system?? alhlskghksd

P.S. Rocla was right. the braided ground strap is for coils. its about half the length of the wire going from the hood to chassis.

[LooN]

Help

[matt]

I think your battery is dead.

[Brew]

Any chance you forgot to ground the engine block? The right side motor mount to the ground point on the frame rail is good location.

[clavinZERO]

we JUST went through this tonight ourselves... on that A/B pic stuff: slit the jacket open and peek in... red = go to power distro block, black/brown = ground that thing. check that out.

[equate975]

I had the exact same thing happen to me. Now I dont feel to bad lol.

I wish I knew what I did to fix it though :(

Auctually, I think I was just a dumb ass and mixed up the positive and neagtive wires, because I shot sparks all over the place. Somehow didnt do any damage.