31 replies to this topic

[tiger99]

You can rule out anything to do with damp, or even floods, as water has too high a resistance, even if dirty, to pass enough current to short the solenoid and make the starter run continuously. Even less chance with oil, which when reasonably clean is a good insulator. Just maybe, SALT water might be able to bridge the ignition switch and energise the solenoid, but not very plausible.

I suspect a simple wiring fault, bridging 12V from somewhere to the solenoid coil. Metallic debris of some sort could do that, at the solenoid terminals or the ignition switch, or damaged wires in the loom, etc. You should be looking for metal to metal contact, not fluids, which might make the task of finding the problem somewhat simpler.

[maieth]

I might have found the cause.

 

Oh my.....

 

 

 

 

 

This is exactly the same cause as the previous electrical issue - badly routed wiring by previous owner. I just feel doubley stupid for failing to notice the wiring was under so much pressure, especially having encountered this problem before.

 

The lower cables to the solenoid had been fed through the tight gap between the solenoid and front panel, in a position where the grille would have been pressing them firmly against the sharp edge of the body work.  This must have finally cut through the shielding that morning.

 

I'm not very familiar with the starter motor set up and haven't traced the wiring, so I don't know exactly what wires suffered this damage, but with enough heat generated to blast a hole in the panel and weld the remaining wiring to the bodywork, I'm guessing this is the main power supply from the ignition or battery.

Presumably the surge created by this dead short was enough to cause the solenoid to immediately re-engage, as someone mentioned earlier, causing the grinding noise, and then continue turning the engine over until the cables burned through completely.

With enough heat to make a make-shift cutting torch, the steam wifey witnessed will probably have been all the moisture from the previous night's rain evaporating from the grille and surrounding bodywork.  The grill now has a nice blueish patina around the fire area, supporting this theory.

 

 

 

SO...

I suspect that setting the wiring right now is going be a spectacular pain in the a**, as all the wires seem to be the same blue and I don't know what they are or where they go, let alone which wires were originally connected where.  Any help or advice on what I'm looking at with regard to wires and connections would therefore be hugely appreciated.

As for the starter and solenoid, is there likely to be any further damage, or is it just a case of fix the wiring and see if they still work?

[maieth]

You should be looking for metal to metal contact, not fluids, which might make the task of finding the problem somewhat simpler.

 

Lol, Found it!!!  :)

[Alex_B]

I think it might be worth buying a whole new loom, they arnt stupidly expensive and will allow a whole new setup which will be routed correctly, without old connectors which can cause an issue as well :) 



Oh and watch yourself on that wiring!!! use gloves as car fires can cause wiring and other bits to become acidic and rather dangerous so use rubber gloves when removing !

Edited by Alex_B, 16 May 2013 - 10:52 AM.

[maieth]

I like the tip about the gloves- good call, but loom is big and scary.  Also pricey, I know they're not expensive for what you're getting, but it's still a very big chunk of money for us sadly.

[Alex_B]

Yeah I have seen some chemical burns on people stripping burnt out cars, with yours it shouldnt be much of an issue as its only a bit frazzled, and yeah they are still quite expensive, but it sounds like its not the first wiring issue you have had so might be worth saving the pennys and factoring it in, and its not that scary to fit, you will need to strip out the dash, and then work systematically through the car installing, its not too bad provided you are sensible :) 

[maieth]

Two further loom questions then.

 

1.) Is the loom matched to the car or the engine?  A previous owner transplanted a 1275 into this car, so I should I look for a loom to suit the right age/model of car, or to suit the replacement engine?

 

2.) Does anyone know of a guide to routing a loom?  I've run some searches, and trawled the FAQs, but found nothing helpful so far.  I'm going to go ahead and accept that the current set up can't all be right, so if we are able to replace the loom I don't want to just put it things back in the same place.

 

Thanks :)

[robminibcy]

The loom is tailored to the car. If you search on minispares for wiring loom and then work through reading each description carefully you'll find the right one for your car. The engines are pretty much The same apart from the coils which will be either ballasted or non ballasted (although this will be again specified by the loom)

 

I found the best way to do this was to lay the new loom I front of the car with the old loom still fitted. Then get as many pics of the old loom fitted as possible paying particular attention to connectors. You will need to take out the dashboard and heater and switches to do this. Then if you think it will help label the new loom so you will know what goes where although I found pictures easier as you can't doubt them. 

 

Working inside out unplug the switches and accessories so that the old loom can be pulled through the bulkhead into the engine bay. You can the start to fit the new loom. Try and unplug as little as possible at a time while still giving as much space as needed to work. This will reduce the chance of confusion and mistakes as you go along. Then working from the passanger side continue to unplug and plug in the new loom.

 

When you finally finish and the old loom is removed check for left over connections and check if nesasery what they are (many cars will have slight variations to cater for factory options that may or may not be fitted) this just makes sure you've not missed anything. Then once happy with it and adter checking the correct fuses are fitted, connect the battery and check everything appears to be ok. Then test all the electrics keeping an eye, ear and nose for anything out of the ordinary. All being well reassemble the car and you good to go. If not have a look at the pictures taken and the old loom to pinpoint problems and hopefully all will be well.

 

You may find some accesories such as radio won't be catered for with the new loom due to having been added later on in the cars life. These will need rewiring in. Again look at how it used to be or if you have doubts as to it having wired correctly have a look on online or ask again.

 

Hope that helped a bit!

Edited by robminibcy, 16 May 2013 - 06:25 PM.

[maieth]

Hope that helped a bit!

 That's a very detailed response and I'm bookmarking it, thank you.  It will definitely be useful!

 

I've had a better chance to examine the damage now, and the good news is that the damage isn't anywhere near as extensive as it looked when taking those pictures.  About 6 inches of cable has been destroyed completely and another 4-5 inches is in a relatively poor state, but still less than a foot of damage all told. The damaged cables are those that pick up on the battery supply at the solenoid terminal and shoot off to various fuse boxes and ancillaries.  As they were taped closely together the whole lot burned through over a short distance. I've followed the cables and used the wiring diagram and found the other ends of each lead, with no further damage or problems.

 

We've got the car booked in for some bodywork in a fortnight, so for now I'm going to repair and replace the damaged cable and we'll check everything over and see if she'll start and run ok.

If all goes well, a new loom is lined up as a definite near-future job. The advice here regarding old wiring and getting rid of POS (Previous Owner Syndrome) is sensible and not something I want to ignore, but the loom is more than we can this month and we'll just use the car less for a bit.

 

As far as repairs go, does anyone know any reasons why 27amp, 3mm cable would be insufficient to replace each of the damaged feeds?  I've read through KernowCooper's cable guides and this seems to be ok, but would be good to be certain.

[maieth]

All did not go well
All burnt out wire has been replaced carefully, and I recharged the battery. When tested, all ancillaries, lights, horn etc work fine. However, when we came to trial start it nothing happened at first. Turning the ignition to 3rd position to start the engine, the ignition lights dimmed, suggesting the starter and solenoid were drawing current, but there was no other sign of them working. A couple more turns of the key and the ignition cable began to smoke and blister
I'm assuming that either the starter or solenoid have failed and the high current, unable to do anything, has just overloaded the cable. Does this sound plausible?

I've disconnected everything again and this time removed the starter motor and solenoid for inspection. Both parts absolutely stink of smoke. Once separated the smell is incredibly strong so something has definitely burned out badly.

Does anyone know what I can do to check over the starter and solenoid to see which one, if either, is dead?

[tiger99]

Which cable exactly started to smoke?

[maieth]

Red and white, low gauge cable running from ignition barrel, via a block connector under steering column, to spade terminal on solenoid.

According to Haynes wiring diagram it's in the correct place.
Most of the cable I had exposed in the engine bay smoked and blistered, exposing more cable I have not found further damage. Imagine it would have burnt out the whole loom if I'd tried the ignition for any longer.

[maieth]

Found a local auto-electricians, so will take per-engaged starter and solenoid to then Monday, see if they can diagnose it.

[tiger99]

OK, the "start command" wire has fried. That suggests that the solenoid is shorting internally, due to having been overheated by the previous problem. If so, you only need a new solenoid, but be aware that the ignition switch and the brown feed to it will have been overstressed and may give trouble now or later.

[maieth]

OK, the "start command" wire has fried. That suggests that the solenoid is shorting internally, due to having been overheated by the previous problem. If so, you only need a new solenoid, but be aware that the ignition switch and the brown feed to it will have been overstressed and may give trouble now or later.

 

 

Yeah, that sounds about right.  I want to be certain the starter is ok as well, so I'll still get to the electricians and then replace what's needed. Don't want to put a new solenoid on and end up needing to replace the whole unit anyway :)

For now I also want to try and run a seperate ignition lead alongside the loom as a temporary fix to replace the dadmaged 'start command' wire, while we get some bodywork done, but a new loom is definitely on the books now. Will keep an eye on the ignition too.