E to I wiring

[dougie30]

does the I engine harness plug into the eta fuse box? or will i have to find an I fuse box?

[jlevie]

That depends on whether your ETA has a round or square C101. If C101 is round the M20B25 harness will connect to it, though you may need to cut the wire going to pin 20 on the body side. And you may need to graft a C104 connector to the engine harness. Both of those are dependent on what production date harness you use.

[low330]

That depends on whether your ETA has a round or square C101. If C101 is round the M20B25 harness will connect to it, though you may need to cut the wire going to pin 20 on the body side. And you may need to graft a C104 connector to the engine harness. Both of those are dependent on what production date harness you use.

i have the round connector on my 1986 325es can u please explain further? im not following like pin 20 and graft? my production date is 12/1985 and im trying to use motronic 1.3 out of an 91 325i plzzzzzz humor me....

[dougie30]

i have the round connector on my 1986 325es can u please explain further? im not following like pin 20 and graft? my production date is 12/1985 and im trying to use motronic 1.3 out of an 91 325i plzzzzzz humor me....

i also have a 86es but i am not sure of the production date, and how do i check to see if i have a round connector or not? im assuming its on the fuse box somewhere.

[Cronopoulos]

Guys,

jlevie is referring to this plug (connects engine harness to chassis harness). Also do either of you have a FSM for your cars?

http://farm8.staticflickr.com/7261/7841786818_fc7229768d.jpg

Also, please read this thread as it will answer 99% of your questions -

http://www.r3vlimited.com/BOARD/showthread.php?t=100939&highlight=motronic+swap+information

[mr.vang]

i heard if your eta is an 87 and get a harness from a 87 "I" it should be plug and play.

[MR 325]

i heard if your eta is an 87 and get a harness from a 87 "I" it should be plug and play.

That's correct. 86 and 87 Eta cars are plug and play using an 87 i/is harness.

[dougie30]

ok so i really want to clear this up... i have an 86 eta with the round connection c101 connector and motronic 1.1, i found a 90 i engine that is motronic 1.3... i understand that this harness wouldnt be direct plug and play so what wires would i have to cut/splice for this to work?

the whole motronic 1.1 and 1.3 confuses me.

and yes i did a boat load of research but i am still pretty confused

[Cronopoulos]

ok so i really want to clear this up... i have an 86 eta with the round connection c101 connector and motronic 1.1, i found a 90 i engine that is motronic 1.3... i understand that this harness wouldnt be direct plug and play so what wires would i have to cut/splice for this to work?

the whole motronic 1.1 and 1.3 confuses me.

and yes i did a boat load of research but i am still pretty confused

I plugged mine right in and the car started right up.

[dougie30]

I plugged mine right in and the car started right up.

Really?? everyone i have been talking to said this wouldnt work because it is motronic 1.3? what year is the engine you have?

[Cronopoulos]

87

[dougie30]

87

yea well thats why it just plugged right in hahah im talking about a 90, it wouldnt plug right in because it is m1.3? or because the wiring harness is different?

[jlevie]

What you are dealing with isn't the difference between Motronic 1.1 and 1.3. An 87 325is has Motronic 1.1 and later 325i/is/ic cars have Motronic 1.3. The engine harness for an M20B25 with 1.1 is nearly identical to later 1.3 harnesses. The differences have to do with the way the car side wiring is set up.

One of the differences is that pin 20 of C101 on the body side of early cars is grounded and as I recall there isn't a wire to 20 on the harness side. But on later cars that pin has some other function and isn't grounded. If connect a late model harness to C101 on an early C101 smoke will come out of the harness when the main relay closes.

Another difference is the routing of the DME START signal and tach & econometer outputs from the DME. On early cars (up to 8/87) those signals were via C104. Which is a three pin connector hanging off the engine harness near the DME connector. From 9/87 on those signals go through C101.

Over the production range of cars with M20B25 engines there were other small changes in the engine harness. The type of oil pressure switch connection changed and early harnesses had the injector, ECT, and coolant temp sensors as a part of the harness. Then that was split off with the wiring for those in a plastic rail with C191 as a connection to the harness. The latest production has eliminated the plastic rail but retained C191. Early cars didn't have an unloader switch in the starter and thus there wasn't a wire in the engine harness for that. Later cars have an unloader switch and wire.

You have an 86, which should have the round C101. If you use the harness from a 325is built between 9/86 and 8/87 (1987 model year) it is plug-n-play. If you use a later harness, clip the wire to pin 20 of C101 on the body side (if there is a wire there). You'll need to salvage C104 from your old harness and graft it into the new harness or reroute those wires to C101.

[dougie30]

wow well that definitely clears things up and thanks for all that info,but this also brings me to ask another question, if i were to buy an engine from lets say a 90, could i use the wiring harness from an 86/87? so i wouldnt have to go through the whole cutting and salvaging the c104 from my old harness?

[jlevie]

Yes, though you will have to deal with the oil pressure switch. Understand that not all that many 87 MY 325is cars were produced, so finding one of those harnesses in good condition can be a problem. You can buy a new harness from BMW, but it will be pricey.

It is pretty easy to mod a later harness.