Installing engine from an 88 735i--Wiring harness questions

[RonDwyer]

I spent the weekend dismantling an 88 735i to get the engine. The harness is a lot more intimidating looking than the one on the 85 M535 I installed in a CS Coupe 10 years ago. I am putting this all in my 77 530i but if anyone has identified what to keep, what to strip out and which wires to connect to make the basics like temp sensors, alternator light, starter leads, coil leads that is willing to assist someone who can ask intelligent questions please hit me back.

Ron

[RonDwyer]

Has anyone done a conversion like this using the later electronics and wiring? I have 4 other people asking me to tell them what I find out. If anyone has done this before that can save me some trouble on cutting open the harness and tracing all the wires then please put up a post and help us keep the momentum here.

I'll even do a tech article. :D

Cheers

Ron Dwyer
Former BMWCCA chapter technical director
Bay Area Region (early 90's)

[DMS]

I have no idea about the american engine harness since the engine I took was off a euro '88 535i. But you can leave the ECU in place the only thing you need to change is the big round plug of which you only need 5 wires or so. It really isn't hard at all but perhaps you can post a few pics of what makes you worry?

[Mike W.]

Think of it as two different harnesses, one for the body, which stays, the other for the engine management, which you need to install. There will be a couple of wires you need to splice, but not many. Body means things like alternator, starter oil pressure etc.

[RonDwyer]

The 88 E-32 harness has some extra spaghetti. It won't be impossible but it sure is easier with some experienced eyes looking at it. let me post a few pictures as soon as i drag it home and get it up on the stand.

Cheers

[wkohler]

There is an FAQ about putting a Motronic 1.0 harness in. I would recommend documenting your progress well enough to create an FAQ. I believe that with the prevalence of B35 cars hitting the yards and available motors, these swaps will become more popular. Look at the response you have already received!

Good luck.

[anthony]

For my conversion to b35, I am using an engine harness from 1988 528e the "super harness". The 88 e32 battery is under the back seat and ECU is under the hood. The 528e is like the e12 with the ecu in the glove box and battery up front. The e32 has more indicator lights than the e12 does eg. Oil level. These wires simply go nowhere. I am going to install the check engine light, it does have basic error codes. It is actually simpler than you would think because the complexity is in Motronic 1.3. Intergrading the wiring to the e12 is the same which is already on the FAQ. Mye28.com has a lot of info on conversion to the b35.

[RonDwyer]

This is starting to get exciting!

[RonDwyer]

When I look at this the connections don't seem all that daunting. There are a few connections at the brain box ares:
1. Motronic multi-pin connector
2. 8-pin connector (likely the gauge & indicator light leads?)
3. Temp sensor for the brain box (Easy to lose this one without thinking about it)
4. Black 3-pin connector (cooling fan to box I recall, make go away)
5. White 4-pin connector (WTF connector)
6. 2 Relay cluster with heavy power lead (fuel pump relays? just need to know how to run my pumps)
7. Ground leads (easy)
8. Coil leads (easy, does the motronic box trigger the coil as well? I could not find a spark control unit if there is one)

At the other end of the harness are the circular multi-pin connectors
1. Diagnostic connector (I believe I can ignore it, but it might make sense to properly remove it from the harness)
2. Body connector (wires identified by color & pin below, it too may make sense to eliminate it and hard wire what is needed)

Pin Main Stripe Gauge Function
1 Blue Thin
2 Blue White Thin
3 White Black
4 Brown Violet
5 Brown Green
6 Green White Med
7 Green Hvy
8 Black Violet Thin
9 Black Thin
10 Blue Yellow Thin
11 White Green Thin
12 Grey Thin
13 Green Violet Med
14 Black White Thin
15 Brown Black Med
16 White Yellow Thin
17 White Violet Thin
18 Black Yellow Hvy
19 open
20 Brown Yellow Thin

And lastly, the O-2 sensor connector by the starter. That can be left alone, it needs no explanation).

Does the stock E-32 Catalytic converter fit the E-12 well enough to connect the rest of the exhaust to it?

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