I'd Like To Build A Complete Oe Engine Management Loom

[jackherer 543]

The thickest wire needs to go to the gearbox, its the starter that puts the biggest current drain on the battery.

 

For testing connect the gearbox earth and temporarily run a jumplead from the engine to the body.

[DrSarty 90 1 Cars]

Two things.

 

Awesome job GLP & everyone else for approaching this commonly feared topic.

 

I would agree with DreamWeaver who like a few others has built a loom from scratch for a new build that it is a tough, brain hurting but satisfying task. I've done it too now and I'm already planning to redo it, as actual fitment reveals some issues.

 

Making a new loom is probably not as tough as trying to make an OE replacement which must mate up with insitu connectors. Hats off to ya.

 

My advice on that would be to NOT TAPE ANYTHING UP. There is some woven cable shielding which is used in domestic AV systems which would be ideal for test fitting. It's a weak weave too, meaning you can thread your wires through it en-masse, and then pick out the wires you need to branch off at various points to get it spotty dog (correct) and apply a bit of tape to mark the branch location. When it's all SD, you can remove it and bind it all up properly.

 

And there's one thing you could use first before buying the other coloured wires from the excellent VWP bods, and that's the pre-made Megasquirt loom I found. It was only £20, and had excellent quality wiring, with the wires labelled with print on at 6inch intervals; it's idiot proof and would work really well. It's from <diyautotune.com>.

 

Again. Grand work.

Edited September 12, 2008 by DrSarty

[GLPoomobile 958]

Farty Sarty - I liked the look of that Megasquirt loom when I saw your pictures of it, way back when. But I dismissed it as I assumed it must be Megasquirt specific. There's no way I could have built my loom for £20 though!

 

Regarding the taping up, I'm not arguing as your idea sounds grand, but what I did was use masking tape to lightly hold things in place while I got it all right. The benefit of masking tape is it rips and peels off easily if you don't wrap it too tight, and you can write on it with Biro. Yes, it got a bit tedious ripping it off to make changes, but overall it's worked for me. Self amalgamating tape on the other hand, well I wouldn't advise applying it until you know you are done, as it's a c*nt to get off again

Edited September 12, 2008 by GLPoomobile

[DrSarty 90 1 Cars]

I dismissed it as I assumed it must be Megasquirt specific. There's no way I could have built my loom for £20 though!

 

Silly billy. They're just good quality wires in nice colours, already labelled up with all the things you'll need anyway.

 

An MS, like a Bosch Motronic, like a KMS etc all need the same things anyway: switched live, earth main, earth sensors, CPS x 2 or 3, coil trigger x 1 or 2, injectors x 2 and on and on again. A good short cut if you ask me, and bags of wire to boot.

 

And as for £20; I never suggested you could old bean, but you could get all the wires (already brilliantly labelled) for that. You'd just need the connectors & some tape then, so maybe £23.42?

 

Seriously. I think you could do this for way less than £50. It's just the time and effort that costs. But then again you've already completed all this work anyway, last winter.

 

C*nt.

Edited September 12, 2008 by DrSarty

[GLPoomobile 958]

But what about the ECU connector at the end of the loom? You'd have to cut it off and bin it, and I don't like waste

 

But seriously, it is a bloody good idea, and kind of makes me wish I'd done it this way. But building mine 98% from scratch has been a damn good learning experience. Fingers crossed it bloody works

 

 

Pork scratching cock.

[DrSarty 90 1 Cars]

^^^

 

No, you don't have to cut it off. It unscrews like the std Pug one (albeit smaller), and you can even pull the wires out complete with metal pins on.

 

Cheese head!

 

[GLPoomobile 958]

Of course it does, that's obvious. I'm just a baw bag who doesn't think

[DrSarty 90 1 Cars]

baw bag

 

. I'm with the 5 Scots battle group out here, and they use that a lot. PMSL

[GLPoomobile 958]

Here's a picture of the loom laid out on my carpet

LOOM

 

What's not shown are the extra bits like the sensor sub loom and connection to the starter solenoid (both on Superseal connectors. I could have done away with the use of sub looms, but since I'd already made them last year prior to deciding to make a complete new loom, I decided to keep them and use them), and then there's the new earth strap, battery -VE lead and the +VE leads to the shunt box, starter and alternator. I've also incorporated another sub loom on a 3 pin Superseal connector, which consists of secondary oil pressure warning light feed (which will go to a 2nd LED), secondary oil pressure gauge feed (going to a TIM gauge) and a secondary starter solenoid wire (the purpose of which is to act as a backup in case of starting problems. i.e. if I'm having no joy with the key, I can take this backup wire and touch it to the battery +VE. It will also be quite handy to be able to start the car from the engine bay this way, for things like compression tests etc).

 

Anyway, got everything back in the car this morning and connected up. The good news is that I have power, and the starter turns. The bad news is:

 

1 - My battery is shot (which I knew), and only gave 20 seconds of turning before dying completely, even though I'd charged it. So not enough time to check things. I've a spare on charge right now, but this one is also pretty nacked, so I'm going to have to bite the bullet and buy a new one.

2 - I had nothing coming from the injectors, and no movement on the tacho when cranking

3 - still no oil pressure warning light, so I'll need to earth the wire and see if it's the bulb that's duff or the sender

[DrSarty 90 1 Cars]

Glad to hear of your success Steve.

 

Sad to hear of starting issues; we all have those.

 

Can't offer much advice re rev counter or oil pressure light other than what you're already doing.

 

Injectors - could be a fuse. One of the wires to each inj will see 12v with just the ignition on; I'd check that and the fuse(s) are ok and that the relays 'click' on ignition.

 

You know the ECU's good right, as you drove it there?

 

So as with all things faulot finding it's just sit down with tea and battenburg cake, think it through and go through it end to end. You WILL find your balls up.

 

Good luck and keep going. I did; took 2 years!

Edited September 14, 2008 by DrSarty

[GLPoomobile 958]

Rich (I'm addressing you directly as it seems to be just us two now )

 

Tonight I came home armed with a new Halfords battery and a plan of attack (checklist from reading CAPS earlier), which went like this:

 

1 - Fit new battery

2 - remember to attach jump lead this time ( ) as suggested by Jackherer, to account for missing earth lead from battery to inner wing

3 - Backprobe ECU pin 18. Yep, 12.5V there with ignition both off and on. A OK

4 - Backprobe ECU pin 35. Yep, 12.5V there with ignition on. A OK

5 - Backprobe ECU pin 20. Yep, 12.5V there with ignition on. A OK

6 - Backprobe ECU pin 20. Turn starter to see if voltage drops to near zero.......

 

...within a second of turning it over, I start to get a chugging noise. Now before, I'd had the injector rail dangling off the slam panel to observe if any fuel was forthcoming, but this time I'd balanced it back in place with the injectors resting in their holes, while I tested the ECU readings. And despite everything being only loosely in place, with no breather pipes connected, and the AFM off the car, that "chug chug chug" noise I was hearing was the sound of one Mi16 trying to come out of hibernation . So not only had I confirmed the presence of fuel (tested rail off the manifold again and all 4 injectors were firing), but I'm obviously getting some sort of spark too. That's good (obviously), because in addition to renewing the entire loom, I'm also using an unknown coil (swapped from a early wing mounted coil to a proper inlet manifold mounted coil).

 

Happiness is a cigar called Hamlet

 

I can't tell you what a relief this is. As a slight off topic, I've been bricking myself as we get nearer the end of the month, as with no MOT, tax due at the end of Sep, and my car being on the public road with no way to move it, and a reasonable list of things to complete, the feeling of stress was pretty high I can tell you! The possibility that I may have introduced a fault/s with this exercise that I could then not track down and rectify, was fairly high in my estimation, so this evening's work has been a huge weight off my mind! I only hope I haven't jinxed it by being prematurely pleased

 

Now I've just got to strip the loom back out, get it looking pretty, put it back in, replace my subframe, wishbones, hubs, brake disks and calipers, driveshafts, TREs, droplinks, steering rack boots, fit the DES SS Grp N system (which needs to be cut 'n' shut), fit new washer reservoir and plug for the pump, new coolant reservoir and hoses, new breather hoses, new wiper blades, sort out the mystery of the wiper sweeping off the side of the screen, bleed the brakes, and anything else that needs to be done pre MOT Better pull my finger out!

[DrSarty 90 1 Cars]

Sweet dude. Your list is pretty long too. Mine was, but with a logical - job at a time approach - you'll eat through it in no time. I'll be happy to come down and help between Nov 7th and Dec 10th if you like as well.

 

Keep going son.

[hexhamstu 9]

resurrected! this topic is great, and should maybe be pinned? (although i think alot of topics should be pinned, maybe there should be a special sub forum for useful threads, or maybe i should get better with searching. ANYWAY)

i'm planning on doing this and recently started a topic and was instantly pointed here.

 

GLP had any problems since? what would you do differently etc....

 

i sort of like the sub loom idea, so you can just remove parts to check over, but will this effect the resistance of the loom?

[DrSarty 90 1 Cars]

i sort of like the sub loom idea, so you can just remove parts to check over, but will this effect the resistance of the loom?

 

I'm perfectly happy to be stomped on for this, but having now built a loom myself (admittedly using an aftermerket ECU), and knowing lots of other people have and do, I'm wondering whether this 'loom resistance' thing is a bit of a myth?

 

Nothing in any Emerald or MegaSquirt manual I ever read said anything about this; so unless the Motronic ECUs are uber sensitive, I really can't see now why it should ever be an issue.

 

......... ......bugger: I've mis-placed my flamesuit.....

[welshpug 1,657]

having a sub loom shouldnt affect things dramatically, manufacturers use them quite a bit.

 

the dreaded brown engine bay multiplug on P1.5 205's,

 

the coilpack wiring on the RFY engines,

 

the round plug on the side of the intake manifold on later P2's (seen it on a 309, not sure if its there on the late 205's)

[GLPoomobile 958]

GLP had any problems since? what would you do differently etc....

 

Sadly I cannot report on that properly

 

After fitting the loom, the grand total number of journeys completed amounts to:

1 - Journey to and from the MOT

2 - Journey to and from a place in Essex (about 20 miles away) to get the tracking sorted

3 - Journey to and from Edinburgh.

 

In that time it was almost faultless. There was the odd 'mumur' on a very few occasions, which ended up becoming an intermittant fault whereby it would cut out and not re-start after a few minutes running. I managed to find out that when it wasn't re-starting it was not injecting at all, and I'd hazzard that it wasn't sparking either. I never got to the bottom of it and the car has sat unused since. Now the weather is on the turn for the better I will start investigating again. It could by a dodgy connection somewhere in the loom (although I hope not as I like to think I did make a good job of it), or it could be a dodgy relay, or it could be something else.

 

The loom isn't even 100% finished anyway as I still need to pull it all back out and make a proper job of wrapping it, as I did it in a hurry just to get to the MOT.

 

As I've said before, I'd advise anyone NOT to be scared of doing this. All you need is the right tools, plenty of patience, and attention to detail. It's not a hard job by any means, but it does take time and it is really tedious, although I also felt really satisfied by doing it myself.

[hexhamstu 9]

ive already got a crimping tool, got a fair few connectors aswell, but none of the specific ones that fit the pug plugs. i have an old 8v loom, need an mi16 loom now and im sorted! would like to redo the whole car but i think thats a bit much and everything works fine so a bit pointless. but i just like the idea of redoing it all so i know what goes where and what condition it is in!

[hexhamstu 9]

can i have a peep at your secret schematic?

[Veero 1]

Digging up an old topic I know but I have done it and built a new loom. It has taken me 3 months to get round to it and after building and fitting it after a few more days wondering why it wouldn't start Doug (d-9) came round and found I had got two pins mixed up on the crank sensor plug so the ECU wasn't firing the fuel pump relay. A day's motoring later and it's all good. It still hunts at idle occasionaly ranging from 800-1200 revs on idle but it starts first time every time and goes like holy s*ite again Now all I have to do is replace the seized handbrake cables (first run round the block I thought it was sluggish only to find the right rear caliper with the handbrake still on and smoke pouring out of the wheel arch) so now it has no handbrake. I hope no-one nicks the bricks off my drive...

 

Anyway if I can build a new loom and it works anyone can. I have a phobia of electronics, as far as I'm concerned it's more some sort of black magic going on in the box with all the pins in. But take your time, measure everything several times before cutting, do lots of continuity testing and all will be fine. I am soon going to translate the 2 row BX diagnostics manual into the 3 row so that we (well Doug wants it mainly) can all use it to find what's wrong with our clunky old French engines.

[Veero 1]

And for reference the crimp terminals that go in the junior power timer plugs are identical to the crimps used in the ECU plugs for later Pugs such as the 406 16v. If you want a newer ECU plug cut one off a 406 in a scrappy, it is very easy to make a pin removal tool and extract all the old pins without damaging anything, then using the crimper from VWP (which does a perfectly good job IMO) it's easy to make a whole new loom including the ECU plug fittings.

[GLPoomobile 958]

Quick update with a lesson learned.

 

Here is the back of 9 pin brown plug under the dash:

 

 

You will notice on the right that the end terminal section is twice the width of all the others. The wire in that location is the switched live. All of the terminals have some amount of movement in the plug, but this one can move more due to the width of the section it sits in. As a result, I was getting an intermittent broken connection if the plug was moved in to a certain position. The wire on this plug is the switched live, so when the connection broke, the engine would cut dead and not re-start (no voltage to coil, ign amp, or either relay).

 

I recommend that the excess space in the plug is bunged with something to prevent the terminal from moving freely.

[GLPoomobile 958]

In an effort to try and make it a bit more easy on the eye, I've just spent the last few hours redoing my loom schematic on Powerpoint, and saved it as a PDF. Whether I've succeded in making it any clearer I'm not sure, but it certainly looks prettier than when done in Excel

 

PDF FIle here

[hexhamstu 9]

Did you use plugs and connectors from VWP?

 

I think I'm going to take the plunge, I already have a crimping tool. So most of the money is already spent.

Edited November 2, 2009 by hexhamstu

[GLPoomobile 958]

I can't remember who I used for what (it's probably back in the topic somewhere), but certainly used VWP for most of it. Auto Eletrical Supplies is another place you can get stuff. I did get some of the JPT plugs from Simtek, because they do them in different colours, so I was able to colour coordinate - blue plug for the CTS, grey for the ICV and injectors, black for all the others.

[hexhamstu 9]

What about Ecu pins? I remember this being mention somewhere in the topic actually. I'm going to read back through now. I also remember someone posting a list of the cars 2-row ecu plugs can be found in. I think it was in one of Leons topics maybe?