M20 Conversion Wiring Help Needed

[Rohil 30]

Hi Guys,

So iv got a fully dressed '87-'88 M20B25 with loom and ecu, gearbox etc all with it lined up. The only problem now is the wiring from the C101 plug which is round and has 20 pins, to my rectangular C101 on the '85 323i. I have started to create a pinout chart which ill upload later tonight, theres just a few wires i am unsure where they should go? There is scarce information about 323i's on the internet, as they were Euro spec and well you know, if its not US spec then no one on any of their forums wants to know about it.

I also need a bit of help as to what will go to the C104 plug (i understand this is for the cluster side of things). There is a round connection on the bulkhead by the passenger side, i know this isnt a C101 as i have an earlier car but i was wondering what it actually is. Any wiring help would be much appreciated. Ill upload my chart so far later on.

This is the first time iv done anything near this intense mechnically, but thought id try my hand at it. I havent got the engine yet but will have it in a month, so i thought its best to prepare everything now so that its easier when i have everything. The 323i L-Jet wasnt the best starting place but its what i have to work with so ill do my best to make it work. If any of you guys are around Central/West Auckland, and know about the wiring id be real keen to have some help when the engine is dropped in. i HATE electrical systems and having not much experience doesnt really help my cause.

Im sure with some help i can get this done successfully, so cheers for any help you can provide me with! Also i know the connector changes around the time this engine was built, so i will check again and confirm. This will probably be the same thread i ask lots of electrical questions over the time of the swap.

Thanks!

[MattA 162]

Swap out the L=Jet and use the Motronic. Or retain all the L-Jet and fit it to the M20B25, it'll work fine I did it on my old E30 many years ago (I was a student and it was the only way I could get it to run without $$$).

I got most of my info/wiring diagrams from the Bentley manuals at the local library, though from my experience they weren't not always that relevant but at least give a start point.

Good luck

[Rohil 30]

Cheers Matt! The L-Jet is gettign swapped out when the engine gets dropped in, its just the wiring to the Square C101 plug that im having trouble with. Im in the same student position as you were haha, hopefully itll go okay! Ill have a look at the Bentleys.

Edited March 11, 2015 by Rohil

[E30 325i Rag-Top 2956]

90% of the wiring is between the engine and the ECU, so provided you have the engine loom and the ECU for the 325i then that is most of the battle solved. The wiring going through the connections to the body loom, like the C101 are things like the gauges on the dash and power feeds.

Pretty sure I have seen a pin-out conversion for L-Jet / Motronic conversion, will see if I can find it.

The mechanical side should be even more straight forward and it SHOULD all bolt up, so no mounts etc need to be fabricated.

[Rohil 30]

Thanks for your input Jon! So Engine and loom and ecu will all be easy as they come with the package and are part of th engine, its just the C101 and C104 that needs a few wires swapped

I have the ECU and loom. Im just a bit stuck on the C101 connections as pinouts iv found say different things. If you could find the pinout that would be great! You have no idea how lost i am with which pinout to believe haha.

Mechanical side isnt too bad, mounts and everything else, everything will drop in and the transmission wiring shouldnt be too hard its about 2 or 3 wires for the reverse lights etc by the shifter.

Do i really have to swap to a newer cooling system? I know they say you cant use the expansion tank and radiator, but would maybe the early one i have now work?

Edited March 11, 2015 by Rohil

[e30ftw 410]

http://www.e30zone.net/e30zonewiki/index.php/C101

+

http://www.e30zone.net/e30zonewiki/index.php/ECU_Pinouts

[Rohil 30]

Plans slightly changed the engine is now out of a '89. Wiring is pretty much the same. Regarding the driveshaft center support bearing. There is an early and a late style, does it matter on the car or the driveshaft? Because the car is an early model and the driveshaft will be from a late model one.

Edited March 16, 2015 by Rohil

[e30ftw 410]

It needs to match the car. Use a pre facelift one so the mounting points line up.

[Rohil 30]

Cheers! Is it possible to use the 318 radiators as they have an expansion tank built into them?

[duvey 245]

Cheers! Is it possible to use the 318 radiators as they have an expansion tank built into them?

From what I understand there are many different types of e30 radiator, but none of them are sufficiently different in size that they aren't capable of cooling any type of e30 engine. The only thing to make sure is that if you have an auto, that you're using a rad out of an auto - they have a build in transmission cooler.

[Rohil 30]

So engine finally has been swapped! However, it tried to turn over and died and now when you put the key in and start it, it jut clicks and doesn't start. Anyone around Blockhouse Bay free on Saturday by any chance to help me out?

When you turn the key all you hear is a click and then nothing, but with the key in position 1 all the lights etc all work fine. Battery is brand new.

Iv found a few things to try try bypassing ignition through diagnostic plug. And bridging relays.

Any other ideas?

[Rohil 30]

Tapping starter yields no results. Im assuming the click when you turn the key means the starter is engaging anyways. But cant be sure

[duvey 245]

I have a mostly intact m20b25 wiring loom you can have if you think it would help.

[e30ftw 410]

Can you crank motor over using a 24mm socket on the front crank bolt?

[Rohil 30]

I have a mostly intact m20b25 wiring loom you can have if you think it would help.

Thanks man, the diagrams i had to wire it up seemed pretty on form. But worst comes worst ill give this a go.

I can crank the engine over with much trouble with the accessory belts on, but once theyre off its smooth and easy to crank over. Mind you i tried this when the engine was out. Would it make a difference if it was in the car?

It sucks that itll be Saturday before i get to it, but ill spending all day and night trying everything i can. So please do keep the suggestions coming through guys! Its much appreciated.

I should maybe have started a build thread as well...

[Rohil 30]

UPDATE: So after bridging the fuel pump relay the fuel pump whizzes, so im saying the relay is dead, is that fair to assume? I have been told the DME relay is the only 5 pin one, BUT my car has 2 5 pin relays? I am talking about the 3 in a row relays by the inner wing to the left of the afm.

Theres a weird connector left over, it comes , part number is 12511706479 called the cable distributor/tszi-control unit, whatever that may be. No idea where this needs to be spliced into? It has one blue and one red wire in it. and comes of the loom which goes from the battery straight to the fusebox.

I didnt bother with the speed or tach yet, but iv spliced the green wire from the c104, to the positive terminal of the ignition coil.

Still when you turn the key you get a big click but nothing else. Also bridging the pins in the diagnostic port i think pins 11 and 14? Its meant to spin the starter but all that happens is you here the relay click.

[polley 916]

Get the engine to crank first, the ECU wont turn on the fuel pump until it gets a trigger signal from the crank sensor (cannot remember if the old m20 setups prime the fuel pump when key first turned on though). The click you are hearing is most likely the starter solenoid, so double check that the solenoid is operating.

If the solenoid is activating then you either have:

Missing ground to engine block (measure ohms between engine block and chassis, or alternatively voltage drop across chassis and block when trying to crank)

Burnt out contacts in solenoid (measure voltage drop across solenoid when trying to crank)

Burnt out starter motor

Engine is jammed ( maybe something got f**ked up when putting gearbox on, or trigger wheel bolts are a common one, double check to see )

Main battery feed to start not connected correctly.

Edited May 10, 2015 by polley

[Rohil 30]

Thanks man! As for grounds iv cleaned all of them and attached them still nothing. I have a slight feeling that after all this it'd the starter, although I am yet to test the cps.

I just want to drive it now haha, iv lined up to take it into the shop.

[polley 916]

Cps will make no difference to cranking.

[e30ftw 410]

Do you have the ground from oil sump to chassis? Have missed that in the past and the starter doesnt crank.

But yeah as above, a faulty CPS will still crank you just won't get any Spark.

[Rohil 30]

Do you have the ground from oil sump to chassis? Have missed that in the past and the starter doesnt crank.

But yeah as above, a faulty CPS will still crank you just won't get any Spark.

Yeah man i have tried that. I even got my jumper leads and hooked it up from the sump to strut tower bolt but still nothing.

Silly question and i assumed no, but does the speedo and econometer gauge have to be hooked up?

Dunno what else to try really, bad starter? Iv hit it and still nothing, unless its completely dead?

[polley 916]

No gauges do not have to be hooked up. Do you have a multi meter?

[westy 614]

Jump starter terminals with a screw driver to test.

[polley 916]

Jump starter terminals with a screw driver to test.

Ha, something I would do. But I've seen certain types of people slip and short it straight to the block, so wasn't going to mention it.

[westy 614]

Best not leave it in gear either...