Help Support Bigcoupe.com

1979 635csi M90 Simple question ECU location

Post here for mechanical and engine topics such as fuel issues, transmission problems, rough idle, exhaust, electrical issues, etc

Moderators: ron, bfons, GRNSHRK

Post Reply
jeme9
Posts: 8
Joined: Mon Feb 05, 2018 10:57 am
Location: Melbourne

1979 635csi M90 Simple question ECU location

Post by jeme9 » Mon Feb 05, 2018 11:47 am

Hello, i have a M90 (1979 635csi) that I am fitting to an e9 (replacing my 3.0 ltr L jet).
in my e9 I have the wire harness in the chase rail with the ECU under the rear seat, however the M90 wire harness is much shorter.

Where is the ECU located in a 1979 635 ? and where does the main harness run on its way to the ECU ?

thanks for your help

GRNSHRK
E12 Based Guru
Posts: 2455
Joined: Thu Apr 08, 2004 3:24 pm
Location: Sunnyvale (SF Bay Area) CA

Re: 1979 635csi M90 Simple question ECU location

Post by GRNSHRK » Mon Feb 05, 2018 4:51 pm

Interesting engine swap jeme9, that should wake up thee old girl just a bit \:D/

The ECU in 6ers is fitted above the glove compartment, and the harness would feed up through into the engine compartment directly above it as well =D>
:mrgreen:
Bobbo
1980 633 CSi
Cypress Green/Pearl Beige
2011 F10 528i
2005 E46 330 Ci ZHP Cabrio
Image

You can never have too many BMW's

jeme9
Posts: 8
Joined: Mon Feb 05, 2018 10:57 am
Location: Melbourne

Re: 1979 635csi M90 Simple question ECU location

Post by jeme9 » Mon Feb 05, 2018 11:33 pm

great thanks very much,
I will study the looms closer and see if I can use my existing loom and keep ecu in the rear, thankyou.
I may have some other questions along the way like understanding the wiring to the distributor and the connector that goes in the side of the distributor on the electronic type, but first I should look for some 635 wiring diagrams to see if I can sort things out, thanks again

duracel79
Posts: 52
Joined: Fri Nov 12, 2010 1:19 pm
Location: Stevenage, UK

Re: 1979 635csi M90 Simple question ECU location

Post by duracel79 » Tue Feb 06, 2018 7:30 am

Worth noting LHD/RHD as you are in Aus.
ECU will be on the right hand side of the vehicle. RHD drivers side, LHD Passengers side.

We are just restoring a RHD 3.0csi ourselves and will be putting in an M30B34 from my old 1983 E24 which is Motronic 1.0.
Contemplating putting a standalone ECU on it with a long extension to place the ECU under the rear seat as original.

HTH

Ben

User avatar
Brucey
6 Series Guru
Posts: 9716
Joined: Fri Apr 09, 2004 7:17 am
Location: Cambridge, UK

Re: 1979 635csi M90 Simple question ECU location

Post by Brucey » Thu Feb 08, 2018 6:03 pm

the L-jet harness is very different from a motronic one; but motronic wasn't used in E24 until maybe 1980. L-jet itself underwent various changes through the production in particular in how the idle speed was regulated.

The location of the ECU varied in E24 depending on the age of the vehicle. Most commonly it is to be found under the RH side of the dash (whether LHD or RHD) but it may be that early cars had the ECU in a different location again.

Note that the engine harness often contains wires for oil level sensing and for things like thermostatic fan switches; these vary with model. It may be easier to re-use the harness from the old engine or extend the harness for the new engine depending on what the differences are exactly.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Post Reply

Who is online

Users browsing this forum: No registered users and 11 guests