Burnt Ecu Wiring

[leon 1.9 0]

Well, since I bought my 205 with a GTi6 engine in it a few months back I've had one or two minor niggles, but nothing serious. However, when I got it I did notice that the ECU was mounted in the engine bay and was held in a fairly crude way.

 

So, one of the jobs on my list of 'things to do' was make a decent bracket up to hold it in a reasonable position.

 

Last night, after a fairly short run, I pulled into the drive where I park. As I stuck it into reverse was a little clumsy on the clutch and stalled it . Shrug, select neutral, stick the handbrake on and try starting it.

 

Engine cranks over fine, but just won't start. One or two splutters but its definitely not going to go.

 

So, roll it back into my parking space and pop the bonnet, expecting it to be moisture on the leads or something else simple, only to find that the ECU has come off where it was mounted and fallen against the exhaust manifold

 

So, disconnected the battery to make sure there was no risk of getting a shock or shorting anything more and had a closer look. There's no real signs of damage to the ECU case, although part of the metal did feel quite warm (could still hold it quite easily though, not too hot). However the main problem is this:

 

burnt ECU plug/ cable

Melted plastic on manifold

 

As far as I can see, the damage is that the manifold's heat has melted through the insulation and back to two exposed wires. There were also one or two small sparks (!!!) off one of them before I disconnected the battery so it was obviously still live.

 

I did notice I couldn't hear the fuel pump prime when I first tried restarting it, but does the pump prime EVERY time you turn the ignition fully off/ fully on again?

 

Next, what to do? I'm planning to try and cut/ melt back the plug plastic around the exposed wires so that I can see which they are. Then I'm planning on soldering in wires to solve any breaks as a temporary measure. Then I can reconnect the ECU and check I have no other ECU or electrical damage? Any other ideas?

 

Longer term I guess I'll have to either replace the whole plug or the whole section of loom... and I hate car electrics

 

 

PS

Woohoo managed to get through the whole post without swearing! Mind you, I swore enough last night.

[philfingers 5]

don't worry about the palstic on the manifold, it'll just smell when it burns off!

 

Not sure on the '6' plugs but the 8 and 16v ones you can undo a little screw on the back and the screws holding the cable gland on (where the wires go into the plug) and take it apart. You should be able to trace the damaged wires to the little terminals. I'd remove the terminals and slide soem heat shrink over the damaged wires. You could replace the plug but I think it would be fine so long as you secure it properly out the say. You could put a bit of tape, silicon sealant over it to stop the water getting it

 

It doesn't look a show-stopper!

 

Phil

[M@tt 77]

you can undo a screw and remove the cable gland on the GTI6 ECU connector as Phil has said, i've done it on mine a couple of times as i had a problem with the pins being pushed in when connecting it to the ECU

[leon 1.9 0]

Yeah, suppose it just depends on whether there's any more serious damage to the ECU or relays etc. Was definitely still click from relays inside as usual when I tried starting so hoping there's nothing too bad!

 

The pic shows a screw on the plug, but the plastic part coming out of it is more 'conduit' style than a gland as such, and goes into a 90 deg plastic bend. A bit of careful sawing/ hacking/ cutting should get it off though...

 

Edit: too slow typing. Ok if it comes off easy it shouldn't be a big job. Phew.

Edited January 13, 2009 by leon 1.9

[MrG 3]

We had a similar issue on our first 205.

But it was the battery that was unsecure (bracket had broke), my wife driving, daughter (about 2yrs old) in the back, going down country lane, nice and narrow when round the corner a lorry appears, brake hard, car cuts out, tries to restart nothing but then loads of smoke from under the bonnet! Wife manages to get daughter out of the back in record time, sits on the side awaiting inferno, nothing just lots of black acrid smoke.

 

Lorry driver jumps out & helps to push the car to one side, pops the bonnet and was greeted by a mass of molten wiring. Battery had come loose or the bracket broke and the battery was jammed against the bodywork! AA towed the car home.

 

We had to have the loom replaced completely under the bonnet; local guy did it from scratch! And when we got it back a week later, everything worked! Including the front fogs which never did as did all the dash lights etc! But I now always check the brackets etc.

[pj838 0]

You should be able to pick up one of the gti6 battery boxes quite easily/cheap, with the ECU holder on the back.

[leon 1.9 0]

agh s*it just realised, if you disconnect an unlocked gti6 ecu from the loom with the battery disconnected, could it relock itself?

 

Edit: thinking about it it had stickers/ warranty seals from 'ecu doctor' or someone so its probably be fiddled with inside previously rather than just disconnected while running anyway.

 

Sorry about the blabbering but I feel lost without a working car!

Edited January 13, 2009 by leon 1.9

[M@tt 77]

no it won't lockitself again, to lock it you'd need all the key/transponder gubbins which you don't have on a 205 so once its been unlocked and runing in a 205 it won't lock again as theres nothing to send it the signal to lock.

[leon 1.9 0]

Ahh ok got it the wrong way round and figured it was loss of signal that made it lock. Of course, if I'd had the sense to think about it I'd have realised that, otherwise you'd be screwed every time you wanted to change a battery etc.

[M@tt 77]

Hopefully it'll be something simple. First port of call is to sort the burnt/melted wires then it will be a case of troubleshooting to see whether it was simnply a case that the wires were shorting hence it wouldn't strat, or whether one of the components/ecu has been damaged by the shorting. but you'll need to sort those damaged wiries first

 

report back once thats done and we can take it from there

 

HTH

 

Matt

[leon 1.9 0]

Well first go at it last night, can't get the plug apart! Is there a possibility that there are different ECU plug types? Although this one does have a screw at the end of the plug (the part furthest from where the loom comes in through the gland), the black section is one moulded piece so it can't come apart!

 

The far end of the orange pull connector itself can be pulled on, but the end closer to the gland seems tightly held in. I think the melted wires have stuck to the inside of the black plug so they won't come apart.

 

If its possible to get a black section of the same ECU plug that can be opened up, then I think I'll probably have to carefully cut this one open and remove it, repair the wiring and then fit a removable black plug.

[M@tt 77]

didn't read you're post properly

 

yeah just try carefully cutting the gland alon its length and peel it off which will hopefully free everything up. you could just wrap around it once you've sorted the dodgy wires

Edited January 14, 2009 by M@tt

[leon 1.9 0]

OK it definitely is melted together then, no matter how much I tried with pliers or screwdriver the one end wouldn't budge. Cracked the black plastic part while trying to get the orange plug out of it too

 

I got the rubber gland end off the plug ok but its the solid plastic part of the plug thats actually melted through/ onto the wires, so I'll have to cut it open to get the wires apart from it.

 

I stopped before I lost my temper with it, otherwise I think I'd have gone mad!

[leon 1.9 0]

Well, found that the plastic on the plug around where the wires were melted was had turned brittle & crispy by the heat. I pushed the wiring inwards to free it from the melted plug and found I could just snap off small chunks of the plastic until I had access to the wires. Then managed to tape up the undamaged wires and do a basic repair on the only one that was properly broken/ damaged.

 

Still no change when I tried starting it though

 

Traced back and have noticed that the double relay isn't operating when I turn the ignition on, so inevitably no fuel pump prime etc. Took the double relay off its plug and checked with a meter to make sure there was power there. Shorted the contacts through to test, but still couldn't hear the fuel pump prime/ run?!?

 

Went back and checked and there is 12V switching at the d.relay coils when I turn the ignition on, but the relay doesn't seem to be operating (noticed the cover seems to be bulging slightly, not sure if thats normal or if its gone pop inside!). I've als o still got a small bit of the white wire I repaired at the ECU accessible, so using the meter I found that when the contacts are shorted on the double relay, there's 12V on the wire at the ECU, but with the relay in place & the ign. switch position on my meter only shows 1.4V (which suggests the relay contacts are dodgey).

 

My concern is that I think looking at the GTI6 wiring diagrams the ECU provides the sink on the neg side of the double relay coils, so a burnt-out/ damaged ECU would stop the relay working correctly.

 

Still doesn't explain why my fuel pump still didn't seem to be operating.

 

Next steps:

- Short the double relay again and test to see if I'm getting 12V at the fuel pump. If not, trace back through 205 fuse box to see if there are any wiring issues there, and where I'm losing the voltage.

- Properly repair/ solder the white wire on the damaged ECU plug.

- Take double relay into work, contact 12V supply onto coil and test whether contacts switch over. If so, ECU is to blame, if not, relay is shot.

 

I'll get there eventually...

Edited January 19, 2009 by leon 1.9

[M@tt 77]

the ECU neg sink is only applicable for one of the relays in the double relay (not the fuel pump one) so you should find you have 12v switched at pin 14 of the double relay and if you bridge that pin with pin 5 the fuel pump should prime/run.

 

EDIT: Also worth mentioning (although you seem to know your stuff anyway but just incase) make sure if you're bench testing the relays you get the polarity correct!! you will blow it up if you get it round the wrong way. i speak for experience

Edited January 19, 2009 by M@tt

[leon 1.9 0]

Ok, thinking about just testing continuity from the double relay across to the fuse for the fuel pump, just to figure out if I still have a break in the wiring somewhere (I think the fuel inertia cut-off has been shorted so need to find out if maybe that short has been loosened or broken while I've been pulling the loom around).

 

If that's ok, will then check voltage at the fuel pump itself.

 

Was concerned that the K light isn't coming on when the ignition comes on either, not sure where this is fed from, but the lambda is also connected along with the fuel pump so maybe thats doing something??

 

The relay coils 'should' be diode protected I thought, but will be a little more careful then.

 

Still should get my 306 back on the road this week so I can spend more time on the 205. The 306 has been sat on my drive for several months and when I first tried starting it the battery decided it would be fun to leak. Always entertaining trying to disconnect a battery and move it while there's liquid pissing from it, not knowing if its acid or water.

[Super Josh 4]

The K light is driven directly by the ECU. So if this isn't coming on it would suggest that the ECU is receiving permanent power, ignition switched power or ground (or any of the above)

 

 

 

Josh

[leon 1.9 0]

You mean that the ECU isn't getting one of permanent live, switched live or ground, right?

 

Could also be from a failed/ damaged ECU too though I guess, as I don't know how long the ECU was leant against the manifold with the engine running (probably not long otherwise it'd all have melted!).

[leon 1.9 0]

OK, had another run through everything last night and found I'd made a balls-up

 

When I'd realised that the double relay wasn't switching, I'd tried shorting it out to get the fuel pump to run. So I looked at the diagram on the top of the relay, which shows one side of the contact 1 going to pins 1 and 9, and the other side to pin 11. Then the second set of contacts had 8 and 15 one side, and 4, 5, 6 and 13 on the other.

 

So logically, short say pins 11 to 9 and 13 to 15, and as all the other pins are linked, then all of the relay wiring is shorted, right?

 

Wrong, of course. The links between pins are in the relay block itself, so when you pull the relay out to get to the loom plug, those 'links' aren't there anymore! So when I'd shorted the two contacts, I still wasn't giving voltage to the pin for the fuel pump, so fuel pump won't pump

 

So I short the right pins and I hear the fuel pump going. Phew! Then the torrential rain and heavy hail started and I packed up and went back into the warm...

 

Pretty sure now the relay is u/s, will check it today but seems that that's also the reason why I won't get the K light etc, because I'll need all the pins made on the relay as they would be if it worked.

 

So, time to find a new relay, I think. Incidentally, if I get some wire links together and short all the contacts as if the relay has pulled in, is that ok for me to carry on checking everything else? Would a working car start with the contacts shorted correctly? I can't think of any reason why not.

 

Edit: Well checked the relay in work and one coil & set of contacts isn't working so seems I've found the problem. Anyone got one? Wanted ad will be up soon.

Edited January 20, 2009 by leon 1.9

[leon 1.9 0]

Woooh its alive!! Changed the double relay over for a new one and she started first time. Funny how miserable I get when I don't have a car and how good you feel when you first get out for a drive again.

 

Crapped myself when I first took it out again as it'd been raining heavily and I came round a bend to find the whole road flooded, didn't realise it was so deep and then couldn't see a thing for a moment as the whole car had a huge wave go over it! Electrics were still fine after though.

 

It feels so good its hard to describe! (No rude jokes!)