Morris Minor Owners Club

I fear my inexperience is starting to show and I was yet again stuck at the side of the road today, peering under the bonnet and understanding very little.

My truck has developed what 'feels' like a misfire and then progresses to losing all power and the engine stopping. It happened last weekend and I managed to restart him after taking off the distributor cap and cleaning the rotor arm. I did check that fuel was pumping ok by taking the pipe off the reservoir and it looked ok.

Today I changed the distributor cap and rotor arm (but not the points or condenser - though I have new ones here). I also checked the points gap and it was spot on. He ran at idle for 10 mins quite happily, but started missing as soon as drove down the road. He gave up completely after about a mile. I fiddled with the leads and cleaned the spade contacts on the coil and he restarted, but very lumpily and I managed to limp home - but he conked out twice in doing so. My fiddling may have had no effect at all and all he wanted was 5 mins rest.

The only other symptom that might be helpful is that when he was running ok last weekend, he seemed sluggish.

So - where to start? I guess it could be a fuel problem but the pump is ticking occasionally and when I'd expect it to - and it seems to pump fuel happily when I disconnect the hose. I'm sure there are lots of things I could check - but where to start? a little guidance for a novice would be much appreciated.

Simon

Firstly check to see if the dash pot on the carb has got oil in it. Unscrew the black cap on the carb pull out the plunger thingy, and gently try and push it back in again. If you get a sloshing sound and the plunger pushes in easily, top it up with some oil... I use engine oil, but others choose a lighter one. Don't top it up too much just enough so it doesn't come over the top and isn't too hard to push the plunger back in again. This may cure your lumpy/sluggish running. If it pushes in with some resistance then it is ok.

There have been problems with condensor quality in recent years. Those problems sound a bit like a condensor braking down. If you haven't already changed it, fit a new one.

there have been dogy rotor arms as well there are 2 types depending on what kind of dozzy you have get a rivitless one .

It's absolutely typical of failed condenser.

I have never known low or even completely absent oil in a carburettor damper cause such symptoms. At worst, it will cause a hesitation on opening the throttle. At constant revs and load, the carburettor piston doesn't move, so its degree of damping doesn't come into it.

Has anything electrical been changed recently apart from the items mentioned? Does the coil look very new? If it will run for a little while from cold, but then needs increasing lengths of time before it will run properly, it suggests something is failing as it heats up - and the coil is a likely culprit. Touch your hand on it next time you get these problems: if it's too hot to touch, there's your problem (perhaps). It's either got internal short-circuits (rare), or someone's fitted the wrong coil (not rare).

Kevin

Thanks for all the suggestions, I have a condenser so I'll change that tomorrow and try it out. The coil was quite warm I think, so that's the next check on the list.

Simon

Maybe it is a good thing that you did not bring the pick up on Wednesday, you would have had a slow journey home. Have you got breakdown recovery? Remind me to show you my under bonnet light installation, you may find it useful!!
A dodgy condenser or coil sounds likely. Check that the HT lead from the distributor to the coil is firmly in place and check that the spade connectors on the coil are secure, I had a coil with rivetted spades which worked loose. Try running the engine in the dark and looking for stray sparks.
Look on the bright side, its all good experience and once you have repaired a few problems the car will start to behave itself.

It's 'never' the coil - they either work, or they don't work, because they have gone open-circuit - there's no in-between!

bmcecosse wrote:It's 'never' the coil - they either work, or they don't work, because they have gone open-circuit - there's no in-between!

May I refer the honourable gentleman to Section B2 of the factory MGB manual, which gives a detailed procedure for testing coils: surely unnecessary if it's as simple as working/not working; resistance/open circuit?

Insulation can break down, and intermittent internal tracking can occur. These can be a function of temperature, and are also, of course a function of the peak voltage on the HT side. High cylinder pressures require a higher voltage to ionise the air in the plug gap, and thus to allow a spark to take place. Cylinder pressure is lower at idle, as the incoming mixture is throttled, so the spark is more likely to occur at the plug rather than internally or externally to the coil, or, for that matter, across a rotor arm, distributor cap, plug cap, or ht lead to adjacent lead or earth. Hence one reason for engines to idle OK, but miss under load.

But you knew all that, Roy, and were clearly just pulling the wossname of a poor b....r who twice had to limp home in a misfiring Silver Wraith, to much embarrassment all round. But for the rest of our readers, btdt, and yes, coils (particularly mis-sold, low primary resistance ones, do fail intermittently.

Kevin

Do condensors vary signigicantly from car to car? I know they're just capacitors so the only variabilities are shape and capicitance. If the remanufactured stuff lacks quality, is there a non-original alternative that would do a better job?

It's 'never' the coil - they either work, or they don't work, because they have gone open-circuit - there's no in-between!

Heh! Love the sense of humour there too

ISTR there are some coils which are designed for mounting vertically, and thus are not quite as full of oil as coils once were. I note that I got through an inordinate number of coils with horizontal mounting (in the standard Minor fashion) from a once reputable dealer, eventually having heard of this issue I got a longer king lead, mounted the coil (on the inner wing, I think), and have never had to replace it since.

When they went, the first symptom of failure was usually an intermittent ignition issue, usually a faint misfire under load; which degenerated into a generalised misfire and then a not-running-at-all-sat-at-the-side-of-the-road-cursing.

Fortunately I had (and probably still have) an RAC donated coil (of the ballast resistor type) kicking around as a permanent get-me-home-or-to-a-motor-factor spare.

The one thing that was really noticable was that these coils got *really* hot when they died.

Well - I put 'never' in inverted commas because - obviously, sometimes, it may be possible to get an intermittent failure. But really - in my experience - the work, or they don't work. They don't generally 'get better' with a wee rest. But condensers DO! They can work when cold - and fail miserably as they warm up. Coils don't fail nearly as often as people think - although I grant you - some of the modern efforts are poorly made and they may well fail as described. A 12 volt coil should be ~ 3.2 ohms on the primary - if it's only 1.5/2 ohms then it's intended for use on a ballasted circuit - and will have a very bright but short (and hot) life if run on 12 volts!! As for condensers - you can easily check by simply adding an external condenser from the coil to ground(on the lead going to dizzy) - even a wireless suppressor will work here!

Refering to faulty coils that was the point I was making about checking the terminals, especially if they were riveted in place.

you lot are amazing

I changed the condenser this morning (and also the points as I had some) and only got as far as the end of the road. Then I changed the spade connectors on the coil to their pairs (not sure why there are two on each side) and she started and ran so well that I went straight past the house and did a quick loop of the village. I then pushed my luck and went to the next village and then the next - ending up about 5 miles away without so much as a splutter.

I think I'll change the coil, as they're not that pricey, and keep the current one as a spare.

So thanks all of you. This is by far the friendliest and most helpful forum I've ever found and one day I may know enough to be of some help on it.

Simon

It's obviously not the coil - it's run perefctly! Just bad connections at the spades. Clean them!

As a matter of interest, when you say you swapped the coil leads between terminals, do you mean you swapped each lead to the other half of the double spade, or swapped each lead to the opposite side of the coil? I, too, can't immediately see why either would make a difference, unless they weren't making a good connection to start with.

If you do decide to buy a new coil, Roy and I are in complete agreement here that you must get hold of a multimeter and check its primary resistance (the resistance between its two spade or screw terminals - not the centre HT one). If it's less than 3 ohms, it's the wrong coil, no matter what it may say on the coil, the box, or the supplier's parts list. I'd guess that Kate's problem with coils was that all her replacements were the wrong type (low resistance, hence excess current and overheating). The workshop manual test that I mentioned refers to the importance of testing in the correct orientation to make sure that tracking will occur if the coil is at all faulty. Oil-filled coils should always be mounted terminals-down if they are to be vertical.

Kevin

autolycus wrote:As a matter of interest, when you say you swapped the coil leads between terminals, do you mean you swapped each lead to the other half of the double spade

Yes, that's what I mean. I had already cleaned the spade connectors without result, but they do feel rather loose. They are riveted in place I think and it was Mike's comment about loose rivets that got me to try swapping them over. I agree, Roy, the coil must be fine and what I've experienced is a bad connection - but perhaps it could a bad connection from the spade to the coil rather than from the wire to the spade (if you see what I mean)?

I will order a new coil, cos they're only £12 and having a spare seems a good idea, but I'll try your resistance test when I fit it.

Simon

Well - the 'new' coils tend to be rubbish! So -if you can - I would just clean the connection with a solvent spray -and then tighten the rivet with a firm bump with a punch and hammer!

I think I'd replace the Lucar connectors before I replaced the coil. You can get them from any motor factors and fit them with a pair of pliers, I did for years before I bought the proper crimping tool.