coil failure

[dudload]

picture the scene - man rushes home late from work full of excitement and anticipation. For it is a game of a generation for scots - beat slovakia and we take a giant step towards qualification for the world cup. His friend is cooking him mince and potatoes and has paid for a weeks subscription to sky sports at his house. Said man picks up his keys and jumps in his (always reliable) Morris, pulls out the choke a bit and turns the key. chugga chugga chugga, splutter, chugga chugga.

oh dear.

anyway i remembered the good advice i'd read on here - checked the rotor arm, dizzy cap, changed king leads, plugs. nothing helped, but surely it isn't the coil (6 months old from accuspark)??? anyway i took the king lead off and held next to the block and hit solenoid - no spark....

thankfully i had a spare coil and put it in, started fist time, yay!

everything was a happy ending as i turned up in time for the slovakian red card and my mince and tatties were still warm (just) and scotland won in the end, but was wondering what on earth has happened here?!

i tested the old coil with a multimeter and across the terminals it's reading 9ohms (my spare reads just above 3) and the +ve to king is 9k ohms (one that works is 10k). when i shake the coil you can hear the oil sloshing around, which doesnt seem right. surely if on its side it will leave one part of coil exposes?

should i send the coil back? is this highly unusual?

[philthehill]

The coil is not fully filled with oil even when new.
Any heat generated will dissipate easily even with the coil on its side.

[liammonty]

It isn’t unusual at all, unfortunately, particularly with modern replacement coils. I wouldn’t waste time sending it back - I would just buy and fit a really good quality one. Unfortunately, advice that the coil never fails that was given on here over many years seems to have stuck - modern ones do fail, as I’ve found out several times myself! And the trouble is that even the more reliable original ones aren’t infallible given that they are all so old now.

[dalebrignall]

well if its 6 months old i would be sending it back or at leas phoning them up , im getting the impression the qualiaty of the parts they are getting is not as good as it once was , my red coil has done 3 years now , and i do carry a spare

[Mark Wilson]

It is possible that new coils are more reliable than Scotland, though....

[mike1864]

Nine ohms is much too high. They should be around 3, plus or minus 10%.

But in any "no spark" scenario I recommend checking the connectors on the SW and CB wires to the coil. Last week I thought I'd cured a breakdown by changing the coil. But when I later buzzed out the "broken" one it measured a perfectly acceptable 3 ohms between the CB and SW terminals, and 10kohms between the output and (either) input. It didn't seem dead after all.

I temporarily re-fitted it, and it ran OK! So I then examined the free connectors, ie on the SW and CB wires. On one of them, I could pull the wire in and out a little bit, and the blob of solder on it was clearly making intermittent contact with the connector body. So I cut them (both!) off, and firmly crimped new connectors on. And kept the "broken" coil as a spare.

I wonder how many people think the change of coil cured the problem, when in fact it was the associated wire-wiggling that actually provided the cure; albeit only for a few days, weeks or months, when the fitting of a new coil again re-wiggled a duff joint into conducting again.

As someone else pointed out, the coils were always designed to lie on their side in this car. And while its dynamo mount subjects the LT wires to a little more stress than an inner wing position, it takes the same strain off the HT leads. And it puts the coil in the fan's cooling airstream.

[oliver90owner]

I wonder how many people think the change of coil cured the problem, when in fact it was the associated wire-wiggling that actually provided the cure;

Only those that don't actually check the coil or check it properly! That might be quite a lot, I suppose....

[geoberni]

I agree with Mike about not always jumping at the 'obvious' i.e. trying to fix a symptom rather than thinking out what the root cause is.

It's a common problem these days in our 'Consumer Society', it's easy to jump at the 'obvious choice' and replace something rather than work out what is really wrong.

In Mike's example, No Spark must be the Coil, but a bit of investigation revealed nothing more expensive than a loose connection.

If you take a look in the original Workshop manual, it states in the Bodywork section ...
"An extensively damaged panel can frequently be repaired quite satisfactorily and more economically by patching rather than by renewing the entire assembly", the legacy of which is why we can get things like door bottoms for our Moggies. I doubt if there is any other car you could get such parts from stock.

Sometimes the parts really are poor quality and have genuinely failed, but that just reinforces our tendency to blame the same part over and over again.
It's like complaining that a batch of fuses are no good because they blow every other day, without considering that there is a fault that is rupturing the fuse, which is simply doing it's job.
So whatever your problem, especially with electrics of a bygone era, it's worth taking a step back and trying to consider alternatives.

[dalebrignall]

i had a breakdown on the m25 managed to pull onto the hard shoulder the wire had come out of the spade connector fitted a new connector and crimped it down went home repair took me 30 seconds its worth carring a few odds and ends to get you home

[myoldjalopy]

I'm not sure that "the coils were always designed to lie on their side" as on SII cars they are bolted to the bulkhead at a slight downwards angle. I wonder why they changed this set-up to fit them on top of the dynamo on the later cars?

[oliver90owner]

They should be able to be mounted in any position - unless marked clearly with the design orientation. There should be sufficient cooling oil to do the job, while leaving adequate space for expansion. Likely some are not filled with quite enough, in the little huts of third world manufacturing establishments, to do the job properly.

I believe some Landrovers had coils fitted with the king lead vertically downwards (likely they can wade deep enough to need any water to drain away?). More likely to lose coolant, while under pressure, if there is any slight sealing problem, of course.

Usual 'buy cheap, buy twice' applies to most tools/spares/etc.

RAB