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1979 635csi M90 Simple question ECU location
Posted: Mon Feb 05, 2018 11:47 am
by jeme9
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
Re: 1979 635csi M90 Simple question ECU location
Posted: Mon Feb 05, 2018 4:51 pm
by GRNSHRK
Interesting engine swap jeme9, that should wake up thee old girl just a bit
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
Re: 1979 635csi M90 Simple question ECU location
Posted: Mon Feb 05, 2018 11:33 pm
by jeme9
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
Re: 1979 635csi M90 Simple question ECU location
Posted: Tue Feb 06, 2018 7:30 am
by duracel79
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
Re: 1979 635csi M90 Simple question ECU location
Posted: Thu Feb 08, 2018 6:03 pm
by Brucey
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