Wiring warning for anyone swapping E30 engines!

[Brianmoooore]

Check pin 20 on the car side - it should have a red/yellow connected to it.
Check pin 20 on the engine loom side. If it has a red/yellow, then everything is P & P.
If it doesn't, (empty), then you need to add a reasonably thick piece of wire from pin 20 to the pin of the white DME relay that already has a red/blue on it.
An '89 car should have this wire in place, but I've just bought a late '89 tourer that shows up with a build date of over 12 months earlier, and this one doesn't have it.

[e30topless]

many thanks Brian I will check and post the progress ...hopefully a fire extinguisher won't be needed

[jbh]

reading this has got me wondering... I'm planning on fitting the newer style motronic 1.3 loom to my tech1 sport so what exactly do i need to look for on this one Brian

[SCOTT325SE]

this is why my dad managed to fry my Sports loom when we stuck the refurbed loom into it.
"happy" wasn't a word I'd have used to describe my emotions at the time. It's funny now I look back at it.

[whipsey]

question for brianmoore ive just checked the c101 plug on the body side of my 325i and there is no wire at all in pin 20 but the engine loom has one

[Brianmoooore]

but the engine loom has one

And its colour is?

[gra325i]

i just experienced the very same fire tonight after trying to start the car for the first time after an engine/loom change now im wondering..what do i do now Brian?..the red/yellow wire coming from the "DME" is now goosed to say the least there is a wire running from inside the fusebox to what i presume is this c101 plug thats melted and i haven't even got as far as checking behind the glovebox yet

Help!!

ps how do i know which is pin 20? as i cant see any numbers on there

[liam012]

Can someone help me out?

I have a friends 318i here with what appears to be loom damage as described in brians post.

So i have a replacement engine side loom BUT it has a brown wire to pin 20 of its plug.

On pin 20 of the cars plug there is also the remains of a brown wire which was burnt out - i traced the damage down throught the fusebox where it is burnt through and actualy seperated to the glovebox but cant see any damage on the glovebox side of the bulkhead!

how do i proceed fitting the new engine side loom?
is it safe to do so or are other components likely to be damaged by that pin20 being burned out.
Also the wire coming from the engine side through pin 20 is going to be connecting to nothing as its counterpart on the other side of the c101 is burnt through - what are the implications of this?

thanks

[e30mtech]

so what your saying is its a live meeting an earth if engine loom has a brown? = bad

red/yellow on engine loom and red/yellow on car loom = all good

red/yellow on engine loom and no wire on car loom = add a wire from pin 20 - to the pin of the white DME relay that already has a red/blue on it. ( do you mean add it to where the red/blue wire connects to the relay?)

at what point is it ok to leave brown wire on pin 20? as it must match something on one car or it wouldn't ever be there?

sorry trying to get my head round this as swapping out my m20 for another and not using either loom as have a better 3rd loom to use.

[DanThe]

If you find a brown wire on the car side of the c101 then cut it out. Thats all you need to know if you are unfamilar with the c101 or general e30 wiring.

[Brianmoooore]

"if engine loom has a brown? = bad". Wouldn't cause a problem, but you're very unlikely to find an engine loom with a brown to 20. Only on very early looms.

"red/yellow on engine loom and red/yellow on car loom = all good" and ABS will work.

"red/yellow on engine loom and no wire on car loom = add a wire from pin 20 - to the pin of the white DME relay that already has a red/blue on it." If the engine loom already has a red/yellow on it, then it comes from the DME relay. If there's no wire on 20 of the car loom, then the car either has no ABS, or the early version. The red/yellow on the engine loom isn't necessary, but won't do any harm either.

"at what point is it ok to leave brown wire on pin 20? as it must match something on one car"
Never. Remove on sight. It's a left over from very early production that was never deleted. Another section of the wire is found (unused) in the injector loom of M20 engines, with just one end connected to an otherwise unused pin on the plug that connects the injector loom to the engine loom.

[Rav335uk]

Would this be on the 316 auto I have, as i'm going to carry out an M30b35 conversion from an E34 Brian.?

[Brianmoooore]

I've no idea from here if you 316 has the wire or not, but as DanThe posted while I was writing my post - if there's a brown wire on pin 20 on the body loom side, cut it out.
If pin 20 of the car loom already has a red/yellow on it, you'll need to ensure that there's a red/yellow to 20 on the engine loom as well, adding it from scratch, if necessary.

[Rav335uk]

OK

[E30_Crazy]

Just to be sure, I'm gonna check this tomorrow. Pretty sure it's ok, as I haven't melted down yet. And might not even be relevant to my swap. Putting a facelift engine and loom/management into a pre-facelift Tech 1 shell and body loom.

Anyone got any reasuring words, or is it best to just check myself in the morning?

[Brianmoooore]

Anyone got any reasuring words, or is it best to just check myself in the morning?

Sounds just the combination that's likely to have the problem!

[E30_Crazy]

Right, ok. How sudden of an incident is this? Smoke and all right away, or is it a sleeper that will eventually erupt when going down the motorway?


Regardless, gonna go check it in the morning. Well, in a few hours, since I'm still up at nearly half past 3...

[ian332isport]

Have you ever tried shorting a car battery with a piece of wire ? This is effectively what happens if you have this problem. It will instantly get hot and make lots of smoke and smell. You won't miss it.

If everything is already connected, and you don't have smoke, you don't have the problem.

Ian.

[Brianmoooore]

The short circuit is completed by the DME relay closing.
I.E. The smoke starts when you turn the ignition switch on.

[E30_Crazy]

Kinda what I was thinking. Already had it running for a few minutes and a quick drive around the block. Now I just need to get the exhuast all situated. Don't much like vibrating in my seat from how loud it is. Sounds like it would be nice, like a massage chair, but more like a bone rattling feeling.

[Human]

I am after some advice please, currently swapping a face lift m20b25 lump into my 318i H reg facelift touring.

looking at pin 20 on the m20 engine there is a brown wire. Pin 20 on the car side of the loom is a red/yellow wire.

The m40 engine loom also had a red/yellow wire at pin twenty.

Am I correct in thinking that all I need to do is remove or cut the m20 brown wire as this is an earth. I really don't want to bugger this up and see smoke. Any input would be much appreciated. Cheers.

[Human]

The car does not have abs.

[Human]

bump

[burnout]

i'm in the same boat as you human but i do have abs so i thinnk i'll cut the brown out of the engine loom and see what happens

[jmc330i]

I am after some advice please, currently swapping a face lift m20b25 lump into my 318i H reg facelift touring.

looking at pin 20 on the m20 engine there is a brown wire. Pin 20 on the car side of the loom is a red/yellow wire.

The m40 engine loom also had a red/yellow wire at pin twenty.

Am I correct in thinking that all I need to do is remove or cut the m20 brown wire as this is an earth. I really don't want to bugger this up and see smoke. Any input would be much appreciated. Cheers.

Cut the brown wire out and tape up the loose end. As you don't have ABS, there's nothing else needed.

i'm in the same boat as you human but i do have abs so i thinnk i'll cut the brown out of the engine loom and see what happens

As above, you'll need to remove the brown but also add a wire for the ABS....

if there is no red/yellow fitted, you will have to add one, between the pin and the terminal of the DME relay that has a red/blue on it.

[Human]

Car is on the road and flying, I checked all the wiring as the opposite of the plugs and completely different coloured wiring. Removed the brown wire and all is good.

Cheers !

[Human]

Cheers jmc330i for your reply !

[Brianmoooore]

Eighteen months late for this reply, but I'll make it anyway.
IF your E30 has a brown wire connected to pin 20 of the C101 socket on the BODY loom, then ALWAYS cut it away. I doubt if there is a single E30 in use that needs this connection in place, and if left will always be an unnecessary potential hazard in the event of an engine change, even if it's like for like.

[jimbom30cab]

Having seen my engine loom go up in smoke today, I can vouch for this being very sound advice Brian.