m20b25 from chromy into a facelift m40b16

[george101]

ive started my engine change engines in. just cant work out what wires ect go where. also there is a 3pin plug that comes off the engine loom by the ecu and plugs into something and i have no idea where it plugs as i never had this on the m40b16 engine. i have no spark and no fuel either.

ive looked everywhere for an answer but has found nothing or i dont understand whats being said. could anyone help me or know where i can find a step by step process on fitting the engine into a facelift e30

[Grrrmachine]

I posted a link in your other thread, and you said you have no idea what you're doing. So I'll try and start with the basics.

All the systems that control your engine are known as the Engine Management:

http://www.e30zone.net/e30zonewiki/inde ... Management

When you change from an M40 to an M20, you need to change the engine management, and how all the engine wires (known as the Engine Loom) connect to the rest of the car (the Vehicle Loom). Fortunately for you, BMW made a Multiplug connector known as the C101 plug, that allows you to disconnect the Engine Loom from the Vehicle Loom quickly and easily:

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

Trouble is, there were two types of C101 plug; they changed over some time in 1987. So depending on how old your M20 engine is, you'll have an older Engine Loom plug which won't connect to your Vehicle Loom plug.

So before we can give you any more advice, we need to know how old the M20 engine is, what sort of C101 plug it has, and what wiring you've already connected.

[Tom_Maverick]

Photos always help! Sadly I'm off on holiday this weekend but I work in Worthing so if you get really stuck I could probably cast an eye over it.. In two weeks!

[george101]

I posted a link in your other thread, and you said you have no idea what you're doing. So I'll try and start with the basics.

All the systems that control your engine are known as the Engine Management:

http://www.e30zone.net/e30zonewiki/inde ... Management

When you change from an M40 to an M20, you need to change the engine management, and how all the engine wires (known as the Engine Loom) connect to the rest of the car (the Vehicle Loom). Fortunately for you, BMW made a Multiplug connector known as the C101 plug, that allows you to disconnect the Engine Loom from the Vehicle Loom quickly and easily:

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

Trouble is, there were two types of C101 plug; they changed over some time in 1987. So depending on how old your M20 engine is, you'll have an older Engine Loom plug which won't connect to your Vehicle Loom plug.

So before we can give you any more advice, we need to know how old the M20 engine is, what sort of C101 plug it has, and what wiring you've already connected.

thanks for helping, right the m20 is 1987 im pretty sure and it has the rounded shapped c101 plug (same as the one on the car loom in the e30 im putting it in) also before i removed m20 engine the engine loom that goes though the bulk head and sits under the steering colum connecting to the ecu had 3 wire plug coming off of it. now this engine is in my facelift e30 this wire has no where to clip into?? any suggestions.

back to the c101 plug the wires dont all match up either and some of the pins dont line up, would this effect it ? also ive heard i might have to rewire it?

[george101]

Photos always help! Sadly I'm off on holiday this weekend but I work in Worthing so if you get really stuck I could probably cast an eye over it.. In two weeks!

ah that sucks, and yeah if its not sorted by then if you wouldnt mind coming to have a look id be greatful

cheers

[Kedge]

Since the engine is a M20B25 it'll have the round C101 plug so that's not an issue i wouldn't have thought, my facelift engine loom works fine in a prefacelift car so can't see why i won't work the other way.

The 3 pin plug by the ECU is nothing to worry about, I've got it in my head that's something to do with aircon but i'm probably wrong on that.

Did the engine run ok before the swap? If everything is wired up ok then i'd be wanting to try another ECU.

**Just reread your original post, as the only thing you need to do for the wiring is plug in the ECU, C101, hook up an earth to the engine and check pin20 there shouldn't be much to get confused about so have you removed the loom completely from the engine??

[george101]

Since the engine is a M20B25 it'll have the round C101 plug so that's not an issue i wouldn't have thought, my facelift engine loom works fine in a prefacelift car so can't see why i won't work the other way.

The 3 pin plug by the ECU is nothing to worry about, I've got it in my head that's something to do with aircon but i'm probably wrong on that.

Did the engine run ok before the swap? If everything is wired up ok then i'd be wanting to try another ECU.

**Just reread your original post, as the only thing you need to do for the wiring is plug in the ECU, C101, hook up an earth to the engine and check pin20 there shouldn't be much to get confused about so have you removed the loom completely from the engine??

engine ran fine before it was removed, ill check everything you said.. also if pin 20 they should both match up? and i have removed the engine loom with the engine when i took it out to place in my e30.

[Kedge]

So the loom remained attached to the engine then?

This is what you need to check regarding pin 20 - http://www.e30zone.net/modules.php?name ... ic&t=83367

[Tom_Maverick]

I did an engine change years ago and had terrible trouble before realising I'd left the earths off!! It's a simple mistake but easily forgotten.. And yeah, I'll check the zone when I'm back and see how you're doing!

[george101]

So the loom remained attached to the engine then?

This is what you need to check regarding pin 20 - http://www.e30zone.net/modules.php?name ... ic&t=83367

yeah loom remained attached. i will check pin 20 also

[george101]

I did an engine change years ago and had terrible trouble before realising I'd left the earths off!! It's a simple mistake but easily forgotten.. And yeah, I'll check the zone when I'm back and see how you're doing!

i will double check the earths too. and ok bud thanks.

[Grrrmachine]

If everything (except the little three pin plug) is actually connected and you're able to crank the engine (as you say "no fuel or spark") then this web page is the next step:

http://www.e30zone.net/e30zonewiki/inde ... oubleshoot

The tools you need are a bulb on a coil of wire and a multimeter. But I have a funny feeling this will turn out to be the CPS and the ICV connectors plugged in the wrong way round.

[Brianmoooore]

The 3 pin plug by the ECU is nothing to worry about, I've got it in my head that's something to do with aircon but i'm probably wrong on that.

This plug probably carries he signals for the engine speed (tacho) and fuel rate between the engine ECU and instruments.
On early cars there is a plug hanging off the engine loom near the ECU and a matching connector hanging down from the loom above the ECU which goes to the cluster. On later cars, both these signals go through the 20 pin C101 plug and socket, along with all the other wires.
This means that you have two wires in the plug near the ECU which need to be connected to two wires in the body side of your C101. You can either extend the wires from the ECU plug to the C101 on the engine loom, or extract the wires from the loom going to your instrument cluster and attach a matching three pin plug to it. You can get this from the same car as the one the engine loom came from, if it's still around.

[george101]

The 3 pin plug by the ECU is nothing to worry about, I've got it in my head that's something to do with aircon but i'm probably wrong on that.

This plug probably carries he signals for the engine speed (tacho) and fuel rate between the engine ECU and instruments.
On early cars there is a plug hanging off the engine loom near the ECU and a matching connector hanging down from the loom above the ECU which goes to the cluster. On later cars, both these signals go through the 20 pin C101 plug and socket, along with all the other wires.
This means that you have two wires in the plug near the ECU which need to be connected to two wires in the body side of your C101. You can either extend the wires from the ECU plug to the C101 on the engine loom, or extract the wires from the loom going to your instrument cluster and attach a matching three pin plug to it. You can get this from the same car as the one the engine loom came from, if it's still around.

ok right so i get that i need to extend 2 of the 3 wires to the c101 engine loom plug to connect to the c101 car loom plug as its a later car to over come this problem, but what coulor wires am i matching them to? and where does the 3 wire go?

[Kedge]

The 3 pin plug by the ECU is nothing to worry about, I've got it in my head that's something to do with aircon but i'm probably wrong on that.

This plug probably carries he signals for the engine speed (tacho) and fuel rate between the engine ECU and instruments.
On early cars there is a plug hanging off the engine loom near the ECU and a matching connector hanging down from the loom above the ECU which goes to the cluster. On later cars, both these signals go through the 20 pin C101 plug and socket, along with all the other wires.
This means that you have two wires in the plug near the ECU which need to be connected to two wires in the body side of your C101. You can either extend the wires from the ECU plug to the C101 on the engine loom, or extract the wires from the loom going to your instrument cluster and attach a matching three pin plug to it. You can get this from the same car as the one the engine loom came from, if it's still around.

Ahhhh yea, for some reason i'd read that the plug was on the car which was why i was getting confused since it's a facelift car.