Thinking of fittng an M42?

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JoshH
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Mon May 25, 2015 11:08 pm

Can anyone expand on this point made in the second post on the thread..?

*Wiring loom requires a swap (2 wires, oil and temp ned swapping) and there is a LIVE off the engine loom the goes directly into and EARTH on the multi plug! (i have it unused on my car the m10 loom and m42, possible fuel pump ign live tho)

Thanks :)
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Brianmoooore
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Mon May 25, 2015 11:30 pm

Unless you are converting some ancient M10 engined E30, ignore completely. E30 M42 engine loom is a direct fit into any E30 with a 20 pin C101, apart from the very important point (with any E30 engine loom swap) of checking out what's connected to pin 20 on the body side of the plug.
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JoshH
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Tue May 26, 2015 10:29 am

Brianmoooore wrote:Unless you are converting some ancient M10 engined E30, ignore completely. E30 M42 engine loom is a direct fit into any E30 with a 20 pin C101, apart from the very important point (with any E30 engine loom swap) of checking out what's connected to pin 20 on the body side of the plug.
I am indeed coming from a 316 carbed M10....however mines an 88 facelift so seems to have the modern wiring loom for fuel pump etc already there?
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TwoTees
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Tue Jan 12, 2016 12:49 am

Hi All
I am looking for some help as to how to proceed from where I am at with this conversion for my son.
His car is a 1990 m40 E30.
I have 1993 e36 m42 including loom, all bolt ons. I can get the ECU if required for cheap.
Have sourced an e30 m42 loom and headers.

Everything is clear except the wiring and ecu and am looking for advice on the best way to proceed from here. (considering e30 m42 stuff is quite rare here in Oz and my mechanical ability was quite good back in days of pushrods and points.)

Should I use the e36 loom and make the adjustments as described below by jmc330i and then get the e36 ECU and stuff around getting that to fit.

Or

If I use the e30 M42 loom with some modification at the engine end to reach etc, can I then use the e36 ECU. Will the e36 ECU be happy without knock signals?
I could possibly get an E30 ecu from the US or UK to use with the e30 loom but I am trying to keep his costs down as he is still a student.

Thanks in advance.
jmc330i wrote:As Brian said, converting the loom isn't difficult and is DIY-able with the info available on here (both the forum and wiki).

The E36 loom for mine was removed from its plastic housing and with a bit of work is now tucked away nicely under the standard E30 M40 loom cover on the bulkhead. All the relays are fitted in place under the loom cover and the diagnostic socket is fitted in the standard E30 location. I only had to shorten wires to make it neat and tidy.

The ECU placement is the only real problem. Thankfully once the loom is out of its plastic housing, there is just enough slack in the loom to get the ECU plug through the bulkhead and close to the E30 ECU mount location, but mounting the ECU will take a bit of thinking about as none of the mount holes match up and the ECU sits at an angle.
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TwoTees
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Tue Jan 12, 2016 4:40 am

willnz wrote: Did you get the e30 m42 ecu with the loom you obtained?
Unfortunately not. Finding one will be a challenge. If I use the e30 loom do you know if the e36 ecu work? This would be my prefered option.

However! Working on the assumption that the e36 ecu wont work with e30 loom and an e30ecu is hard to find, I am thinking that using the e36 loom and ecu might be overall easier. That way all the senders on the engine including fuel injection rail will be correct for the ecu. In my travels over the internet I have seen a diagram for the c101 plug change.
willnz wrote: If the body loom has a brown wire to pin 20, cut it away from the plug before you connect the engine loom or you will have a fire!
No ABS. So even if I go e36 loom and the brown wire is at pin 20 on the body loom, shall I get rid of it.

Another question that I realized today is the the crank and cam sensors are the same plug and where they plug into the loom they are also exactly the same plugs. Is it important to plug them in the correct way? There is no way you can tell the difference.

Thanks for the help.
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TwoTees
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Tue Jan 12, 2016 8:39 am

willnz wrote:1. e36 ecu will work with the e30 loom.
Excellent. I will use the e30 loom.

willnz wrote:3. sensors must be plugged in correctly. It is easy to work out which is which with a multimeter.
I must be going blind. Just had a better look at them and they are slightly different. 1 has 1 raised ridge and the other has 2.

willnz wrote:This is a conversion that has been done many times by members on this forum. No need to trawl the internet, you will get all the answers here.. :wink:
I searched using google and Yahoo using very specific and also sometimes general search criteria and this thread never came up. Lots of other sites with bits and pieces of info but nothing as comprehensive as this thread. I actually logged on to ask the question and there it was, right at top as a sticky.

Thanks you for your time. Hopefully I will be OK from here. I should be able to work the engine part of the loom out. M40 is now out and the M42 is in place. My learning curve now will get very steep. ':eek:'
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mark_i
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Tue Jan 12, 2016 11:49 am

Hi two tees.
if you're in Sydney, i'm happy to help.
son and I have worked on a few M42s including head swaps and engine transplants.

Still have a factory stock iS as a daily if you want to see how it all looks.
Mark
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TwoTees
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Wed Jan 13, 2016 3:55 am

Hi Mark,
I'm in Canberra but thanks anyway.
I think I may have located one here I can get a look at. It was a conversion but using all e30 engine and parts.

I need to check that the lower radiator hose in/out are in similar location to my sons. If so I will just order an e30 318is hose as the m40 one is a bit twisted. Top one was an e36 lower hose and fitted well.

Cheers and thanks for the offer.
Chris
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mark_i
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Wed Jan 13, 2016 8:47 am

OK...no worries.
Keep in mind that when doing an engine swap you will want to upgrade suspension and tyres to take advantage of the M42.
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TwoTees
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Wed Jan 13, 2016 11:32 am

Yes, he is already is running better suspension and semi slick tyres. He has been using it for hill climb club days and doing quite well for what it is. He is only 3.5 seconds behind the Toyota 86 crowd with m40. He should be giving them a nudge with an m42. Probably brakes will be next.
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TwoTees
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Thu Jan 14, 2016 12:04 am

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Can I get some help again please?
Attached is a picture of the original M40 ecu plug with 2 extra plugs.
The e30m42 loom that we are using only has the black plug but no white.
The white one on the body side comes from the rear of the car.
Can anyone tell me what this is. will it stop the car from running.
My first guess was speed sensor but that only has 2 wires of a different colour.
The 3 wires are brown, Green/purple and Black/brown. The green/purple goes into the engine bay and the other 2 go to the ecu.

Thanks, Chris
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Brianmoooore
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Thu Jan 14, 2016 12:22 am

Both plugs will not be used in your application. They are for aircon, EH auto. gearbox, etc.
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TwoTees
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Thu Jan 14, 2016 7:54 am

Thanks for that. Started it this arvo. Fired straight away but the oil light is on. There is plenty of oil splashing around in the rocker cover.

Should I have used the e30 sender?
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Brianmoooore
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Thu Jan 14, 2016 9:53 am

Oil pressure switches are the same for the E30 and E36.
The sender is just a simple NC (normally closed) switch, which connects the wire from the oil pressure light to earth (engine block in this case) when there is no pressure, so the first test is simply to disconnect the wire from the switch, and check that the light stays off when the ignition is on.
If it is still on, you have a wiring fault, but if it goes off, either the switch is faulty (not uncommon, but usually accompanied by an oil leak) or the engine isn't developing oil pressure.
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TwoTees
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Thu Jan 14, 2016 11:55 am

Ok what I think I have done is connected the temp sender to the oil light. When the engine is cold there is no light then as it warms up the light glows brighter and brighter. Thats why when it first started it the dash lights all looked good.
When the ignition is first switched on the temp gauge goes to full, then when it starts it goes to off just like an oil light going off and doesn't go up when warm. Bugger! Thats a lot of work to fix a silly mistake.

Took it for a gentle drive around the block and it ran nice but when it got to normal operating temperature it started to pop and crackle and loose power. Will those 2 sensors send a signal to the ecu causing it to do that? or may I have another problem to chase?
Thanks, Chris
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Brianmoooore
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Thu Jan 14, 2016 1:48 pm

Definitely the two plugs are swapped over.
Neither of these two sensors are connected to the ECU, and don't affect the running of the engine, although you will need to use an E30 'brown' temp. sensor to work the E30 temp gauge.
There is a second ('blue') coolant temp. sensor that feeds information to the ECU (same part on E30 and E36), and if this was faulty, or left unconnected, it would give similar symptoms to the running problems you describe. Take out a spark plug and see if it is sooty.
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TwoTees
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Thu Jan 14, 2016 7:19 pm

I did read earlier in this thread about the temp senders and swapped both m40 ones into the m42.
I might put the e36 blue one back in and have a good look at the wires on the loom.
Is there a test I can do when I get to it to check continuity on that blue plug and the sensor?

On a further issue the e30m42 loom that I used had identical sockets on the box for the crank and cam angle sensors. The e36 leads were different. crank had a single ridge and the cam had 2. The crank lead will go into either e30 socket but I had to file the 2 ridges off the other to make it fit into the other socket.
I just took a punt and plugged them in and figured if I had trouble starting I would swap them.
Is it possible if these were the wrong way around it would still start and then contribute to the problems described above.

Its a fair bit of work to get to the wiring loom so exploring all options before I get started.
Thanks for your help so far.

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TwoTees
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Fri Jan 15, 2016 4:42 am

Thanks Will!
The young bloke is away for a few days so I will leave it until he returns so he can see what's going on.
Is there somewhere I can find all this info online so I don't have to keep asking.

Once again thanks for the help.
Chris
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Fri Jan 15, 2016 7:26 am

Brianmoooore wrote:Unless you are converting some ancient M10 engined E30, ignore completely. E30 M42 engine loom is a direct fit into any E30 with a 20 pin C101, apart from the very important point (with any E30 engine loom swap) of checking out what's connected to pin 20 on the body side of the plug.
+1

Easy conversion, I've done it, the results are superb
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TwoTees
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Wed Jan 20, 2016 10:21 am


bobbin1982
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Mon Aug 22, 2016 8:06 pm

Going to start collecting parts for this when christmas is out of the way winkeye

Have an M40 so should be relativly cheap
Driving my digger!!!!
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raso_i
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Sat Jun 30, 2018 11:50 am

hi everyone, long time no post here. I just swaped m42 into my m40 e30 and I want to know does my ecu has ews? its grey labeled bosch dme 1 743 250 001 from 1995 e36ti, can anyone help?
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jwetering
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Thu Dec 27, 2018 5:58 am

Hello;

I've just taken a leap of faith and bought a 200,000 km M42, with gearbox, wiring loom, and ECU which I plan to install in my North American 1985 318i.

My car car has installed a K-jetronic fuel injected M10B18 engine - it isn't clear to me whether this configuration was sold in the UK - but it was relatively common over here.

I've been reading a ton and it clearly has been done but I have one question that hasn't been answered - will the gauges in my stock dashboard work or are the m42 e30 dashboards unique ?

I'd also like an easy how-to guide to fix the wiring but I suspect I will be writing one rather than reading oje.

Thanks


jasper
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Brianmoooore
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Thu Dec 27, 2018 10:22 am

Welcome to the new and revamped one!
Shouldn't be any problems with the gauges. You're swapping a four pot for another four pot, so even the rev. counter will work correctly without any changes.
The engine loom of your M42 (assuming it came from an E30) will be fitted with a 20 pin C101 plug that makes all the connections to the car, apart from the two connections to the battery. Your car probably uses the original rectangular engine loom plug, supplemented by a small three pin plug added to carry signals that weren't present in the original E30 design.
It looks daunting to sort this out at first sight, but the wires and their colours are largely the same, so it's just a simple matter of some soldering and heat shrink insulation. You can either splice your old engine loom plugs to the new loom, or obtain the body half of a 20 pin C101 with a few inches of wire attached, fit that to your car next to the fusebox, and then make all the splices inside the bottom of the fusebox.
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Wed May 15, 2019 10:53 am

Hi,

I've been thinking for quite a long time about fitting an M42 instead of the trusty old M40 in my E30. This thread proves really useful, thanks to anyone who contributed, cheers!
I have but one question: I know that the M42 block features oil jets, while the M40 does not. Are there any more differences between the two engine blocks? Just for clarification: My M42 will be a stroker made with an M47 crank, and I'd like to use an M40 block, just because of MOT restrictions here. Is there any downside of using the 1.6 block? Can it be swapped out without any modification?

Thanks in advance!
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