Injector loom nightmare, wiring advice needed!

Post Mon May 05, 2014 12:24 pm

I've had lots of problems with the loom on my m30 conversion and I've Swapped on an e30 325i loom. Still there were running problems, my mate identified the injector loom socket was stuffed, rusty and wires falling apart. He fixed it and it was fine and then the problems returned. More bad wires in the socket. I pulled the loom off, cut the socket out completely and soldered/heatshrinked all joins but it's still not firing all injectors and I know I've messed up somehow.

I have six wires coming from the engine loom:
Red white
Brown white
Brown yellow larger gauge
Brown yellow smaller gauge
Brown purple
Brown red

From the injector loom I have 7, with an additional brown orange.

I can't find a matching brown orange on the engine loom so I think I may have got the brown yellow mixed up. I have joined them all but brown orange.

Does anyone have a wiring scheme for the injector loom? Or any advice?

Post Mon May 05, 2014 12:25 pm

Also I have a black green loose that I can't find a home for on the engine loom...

Post Tue May 06, 2014 6:58 am

That makes perfect sense, that's how I've wired them up. The only thing is I have a spare wire, you named 6 but I have 7 on the injector loom, I have two brown yellow, one as thick as brown white and the other as thin as brown orange. I can well imagine I've mistaken brown orange for brown yellow on the main loom and connected this to the smaller brown yellow from the injectors.

Post Tue May 06, 2014 10:13 am

Thanks for the info, I think it's time I invested in a multimeter... I'm right in thinking I would pull out the ECU plug from inside the car so I can put one end of the meter on it and the other on the dodgy wires?

The brown/orange is currently unconnected, so I will simply run that to ground, if that's correct? Would this cause serious problems in running?

The black green from my understanding isn't essential? IE wouldn't stop the engine from firing and running?

I am half tempted to get another guarenteed working 325i loom if I carry on having trouble

Your help is most appreciated

Post Tue May 06, 2014 11:12 am

Use a piece of ordinary wire to extend your meter lead to the ECU plug where it is. It's advisable to disturb as little as possible when electrical fault finding in case you 'cure' the fault without finding where it is, only for it to return at a later date.
ECU plug pin numbers are marked on the ECU itself (end of rows only), so carefully work out which pins on the plug are the ones you want, and mark the pins with a marker pen. Don't force anything large (like a meter probe) into the buckets of the ECU plug, or you will damage them.
Without the brown/orange wire connected, the 'blue' temp sensor won't be seen by the ECU, so the engine will be badly over fuelling, as the default is 'extremely cold'.

Injector loom plug:
Pin 1/ Thin brown/red - blue temp sensor signal.
Pin 2/ Thin brown/orange - blue temp sensor earth.
Pin 3/ Thin brown/yellow - brown temp sensor earth.
Pin 4/ Thin brown/purple - brown/temp sensor signal.
Pin 5/ Thick red/white - 12 volts+ ignition switched live to all injectors
Pin 6/ Medium brown/white - signal from ECU to injectors 1,3 and 5.
Pin 7 (centre) Medium brown/yellow/ - signal to ECU to injectors 2,4 and 6.

Pin 3 only appears on the injector side of the loom. The brown temp sensor was changed from a two pin device to a single pin that earths through the engine block, so the wire on the engine loom side, which originally went to pin 20 of the C101, was deleted.

Check that your thin brown/yellow on the engine loom isn't actually brown/orange.

If your starter motor does not have provision for connecting the black/green at the C101, then you can fit it with a 8mm ring terminal and connect it to the inner large stud on the starter solenoid.

Post Tue May 06, 2014 11:39 am

Legendary advice from Will and Brian, I know exactly what to do now

I will report back.

Post Sat Jun 07, 2014 8:11 pm

SO... I'm confused. The injector plug was again in a right state on the previous M20 loom, I attempted to solder the wires and ditch the injector plug altogether. I plugged it all in and it still was running on 2-3 cylinders. I decided my dodgy soldering was to blame so I bought a new loom from a working E30 325i.

I adapted it for the M30 and firing up it was back up to 6 cylinders, although it was running very roughly. Happy days I thought, and left the engine to move onto other things on the car. A few days later and the cylinders dropped like flys! Its back to running on 2-3 cylinders and I'm baffled.

I got my newly bought multimeter out and tested the current loom this afternoon. Continuity on ECU pin 16 to 1-3-5 was perfect as was ECU pin 17 to 2-4-6, this is through both sides of the injector plus and up to the brown-white/yellow wires on each injector plug, this is with all plugs OFF the injectors.

However what threw me is when the plugs are connected to the injectors I was getting continuity from ECU pins 16 to ALL connections on the injector plugs. In other words with a wire in pin 16 on the ECU connector, continuity was reaching not only the BR/WH wires in the injector plugs 1-3-5 but all RD/WH pins in 1-6 and the BR/YL pins in 2-4-6.

I came to the conclusion this is normal as I tested the exact same scenario with other M20 loom I knew was working. As RD/WH is 12v and the browns switched grounds, I assumed I could see pins other than BR/WH as the signal was coming through RD/WH.

So as far as I can tell, the signals from ECU pins 16 and 17 are functioning correctly. I haven't tested the 12v signals from RD/WH or any of the relays. I guess that's next!! I have bought some noid lights to clip into the injector loom so they may highlight if the injectors are working or not once and for all.

I've also checked spark on all cylinders and it seems fine.

Can anyone check my ramblings and see if my thoughts are correct??? Thanks!

Post Mon Jun 09, 2014 7:50 am

I'm a f**king idiot!! It was out of petrol... It have the same symptoms when I had the broken injector loom (it had petrol at that point!) so I didn't even think about petrol. It's now running on all 6 and seems alright! Still seems a bit rough but it will do for now.

Post Mon Jun 09, 2014 8:29 am

Well done mate, it will soon smooth out after a good thrash

Post Mon Jun 09, 2014 9:32 am

rob0r wrote:I'm a f**king idiot!! It was out of petrol...

It happens to all of us! Last year the same car of mine (a BMW, but not an E30) was recovered once on a flat bed, and once on a tow rope after breaking down on two separate occasions.
On both occasions the reason it had stopped was that it was out of petrol!