Morris Minor Owners Club

Hi all, I'm sure you can help me with this problem.

I havent been able to use Sky for a while now since she broke down in a car treasure hunt in the pouring rain.
We were going fine until the engine began missing and completely died, I assumed damp, due to the rain, and dried everything out after which she started again but kept repeating this every few miles.
Eventually got home where she stayed until last week when I got a chance to take a look. Everything completely dry, so drove her out and as soon as I'd done about a mile she started to die with a bit of back firing. Left for a few seconds and I struggled back home.
Checked the timing -static- and all seemed ok.
replaced the condensor and tried again with no improvement. Replaced the dissy cap and leads with ones which were working before I serviced her a few months ago and no difference.
Replaced the coil with a spare snd still the same problem.
Fuel is getting through ok with the bowl full.
Any ideas?

Coil wiring or the little wire inside the dizzy shorting out....?

I've checked that the coil is correctly wired, and it is and the little dissy wire appears ok but I admit I havent changed that one so it might be worth trying. In fact I did re-make that one with standard cable a few moths back when I noticed that the old one was only holding on with a couple of cores. I can try re-making it with 84 strand to see if it makes a difference.

Brian

Did the problem start soon after you changed the wire before?

No. We've been to the National, around Weston-Super-Mare and back since then.

Ahhh.... did you change anything else recently?

No, not before the problem started.
Since then I've started trying to change things to find the fault. The only slight suspect is the coil because I changed that for the coil that was on Molly which I've never had running (apart from tick over when I bought her). I also had to use the dissy cap and leads for that because her coil is the old screw in ht type.
Might just have to buy a spanking new coil and try it.

It certainly would point to coil but I think you would be very unlucky to have 2 showing the same fault.....

has the rotor arm got a rivit on it,thease can short out

I think Dale has hit the nail on the head - you don't mention changing the rotor arm - it's the FIRST thing to change ! It's almost NEVER the coil - and you've tried another one anyway! Fit another rotor !

Dale / bmc

Thanks guys I'll try them next. No I havent tried the rotor which I changed in the service. I didn't even consider that this could be part of the problem.

I'll take a look tommorrow.

Brian

if you have a 45d distributer then mini spares do there own without the rivit.there is also a firm called distributer doctor i think they do them for the 25d type hope this helps .

Thanks Dale

Well the rotor arm isn't a riveted type (Lucas type fitted), but changed it for the previous one anyway but with no effect. Also swapped for another coil just in case and also with no effect.
Adjusted the timing to give the best tickover and replaced the vacuum pipe just in case.

It ran a little better and we were able to get the revs up a bit higher before it started giving up the ghost.
This time when it fails it will at least tick over but not run at any speed. We can limp home by keeping the revs to a little over tick-over.

I'm going to remove the in-line filter when I get the next chance to work on it, just in case it is starving at any revs. (Although it seems fine on the drive)

Brian

Hmm - I had bet my shirt on that rotor arm! You have changed all the ignition stuff (have points been changed ??) - so it really MUST be the fuel system now!

I had a similar problem on my pickup recently, it would misfire only occasionally and unexpectly, I mean, i wasnt pulling away from lights or junctions etc, when I expect it to play up, but it usually misfired at speeds around 40 - 50mph.

I changed everything including the carb dashpot oil to 3in1 which did actually make matters better, but the misfire came back in avengence, dist cap, rotor arm, leads, plugs, points condensor etc, not much left to change so I changed the aging coil (date stamped august 1974) so it must have been the coil its the only thing left I thought.

So the saga started.
I bought coil number 1, only for it to be totally dead and the engine didnt start at all, so back on went the original coil. Exchanged the 'new' coil for coil number 2. This time it started but the engine ran like a total pig misfired/backfiring/no power, the works, so again the original coil went back on.

Anyway today I recieved coil number 3 this time a lucas and guess what its sorted, no annoying misfiring or anything nasty, but it took me three coils to find out.

Dont rule out your coil just yet, I agree with others that its very unlikely to have two dodgy coils, but Im afraid it happened to me and they were supposed to be new units. But perhaps Im just unlucky, and those two coils were'nt lucas units, they were both made by the same manufacturer.

Regards

Steve B

Did you by any chance megger any of the coils ? Just interested to know the resistances!

Hi BMC
I did, the working but dodgy 1974 unit was 3-4ohms between the two LT terminals. Coil number 2 however wouldnt keep a steady reading, I think it averaged out at around 1.2ohms. The new and working 3rd coil was giving a similar reading to the 1st at 3-4 ohms. All coils both gave an open circuit on the HT windings.

Not totally sure what I was reading exactly, but I measured between one of the terminals and the casing. The 1974 unit gave me 7 ohms, number two gave 5ohms and the working 3rd gave me 8 ohms.

As you can see they're no obvious great difference in any of the readings really, other than the 2nd didnt give a steady LT circuit reading, so perhaps thats why it wasnt working properly, there may have been some sort of sort circuit within it. Dont know what difference it makes but the 2nd did get very hot to touch when I initally installed it on the engine.

Dont know what the difference is between the 1st and 3rd coils though. However saying that the 1st coil did work and only misfired occassionally at higher revs so it must have some sort of fault somewhere.

Regards

Steve B

Ahh -interesting! The #2 coil seems to be for 6 volt operation - and it would indeed get v hot - and would be producing a v high HT, possibly causing sparks to jump where normal HT would not! The intermittent connection was probably just a bad connection - possibly exacerbated by running a 6 volt coil on 12 volts! So - that really means that your new coil is the same as the original coil - same ohms (~ 3.2ohms is correct) and it works. So - I would now go back to the original coil -which is giving perfectly good readings - and try it again! I suspect there is nothing wrong with it, and generally moving about all the connections (and possibly the burst of v high HT running!) has cleared up the problem - at least for now.

BMC

Are you talking about a megger test (ie insulation) here or a straight resistance test?

Just interested as I'd like to test the coils that I have. I still have my megger from my sparky days, so can do the insulation test.

Brian

I used the term 'megger' out of familiarity - but it certainly would be interesting to try it at 500 volts - although my own wee meter only tests at 1.5 volts!