won't start - now intermittent loss of power

[alexmcguffie]

The wrong coil would never damage a condensor.

[bmcecosse]

I'm not so sure Alex - the increased current through the low impedance (wrong) coil will produce a much higher back EMF when the points open. Could just tip the condenser over the edge!

[chickenjohn]

It very much CAN be the coil. Modern parts being what they are, modern coils are much more prone to fail.

OTOH, you have not mentioned the points. do they open on the cam?? Pitted/ burnt contacts??

And a failing low tension lead can give exactly the symptoms you describe. The lead may look OK but the crimped end can start to fail. Test with a continuity tester.

[bmcecosse]

A complete new dizzy from Accuspark/Simonbbc could be on the car this morning if it had been ordered when the trouble first started. In my experience - coils either work, or don't work - they don't come and go... and a different coil has been tried here without making any difference. Loose connections/damaged wires etc are always possible - and much more likely to come and go. I've said it over and over - but will repeat again - my 'never the coil' mantra is only intended to encourage folks to check everything else first, before automatically replacing perfectly good coils. Of course it is sometimes the coil.....but very rare with good old coils. I have no faith whatsoever in 'new' coils. Especially if they are wrongly specified for the 12 volt system.

[LouiseM]

you have not mentioned the points. do they open on the cam?? Pitted/ burnt contacts??

And a failing low tension lead can give exactly the symptoms you describe. The lead may look OK but the crimped end can start to fail.

The points opened on the cam and are clean and unpitted. I considered the LT lead so bought a new one at the rally just in case.

and a different coil has been tried here without making any difference.

Trouble is that the problem was intermittent so very difficult to diagnose.

After leaving home on Saturday morning all seemed fine but the same lack of power / misfiring happened again after about 12 miles. The man with the recovery truck also works as a mechanic on classic cars and having checked the points and all leads concluded that it was most likely a coil failure (it was very hot). The car was running but it was felt that the problem was likely to return so best bet would be to recover it to the rally where I would be able to get a new coil. So I arrived at Kelmarsh via tow truck.

Bearing in mind there have been a few posts here recently regarding exploding Lucas coils I wanted to make sure that I bought a 'good' one. Jon (site admin) spoke to one of the traders who advised that all new coils should be mounted upright. Apparently to save costs they are not completely filled with oil and if fitted on their side there isn't enough oil to cover all of the coil internals so it overheats and goes pop! So purchased and fitted a s/hand coil which was said to be good and fitted it in the same place as the previous one, mounted on the dynamo. The previous coil was an intermotor one and looked to be fairly new.

Anyway, all seemed to be running fine after that so it seemed that it was OK although I hadn't driven it very far so it hadn't had a good test run. All was going well on the journey home yesterday afternoon until 20 miles into the drive when the same problems occurred again - lack of power and misfiring - so I pulled off onto a slip road. I checked all the connections again and this time the car wouldn't restart. By that time it was pouring with rain and my mobile phone was dying as I hadn't been able to recharge it at the rally. I tried ringing the recovery service again but kept being put in hold as all the operators were busy

As luck would have it a man in a green traveller come off at the slip road and stopped to help. He thought it sounded like an electrical fault so checked all the connections but it still wouldn't start. A check of the fuel pump showed that it wasn't ticking and the points weren't opening either. Fortunately he had a spare (new) fuel pump so fitted this but the problem still continued. Although the fuel gauge was showing a quarter of a tank he thought it was possible that it was misreading and there wasn't enough fuel getting through so drove off to the nearest petrol station to fill up a can. At that stage a Police car drove up to check if I was OK.

After putting more fuel in the car still wouldn't start and at that stage a flat bed recovery truck arrived to move the car - there were roadworks on the A14 and I had stopped just short of the 'free recovery ends here' sign. So Eric was loaded onto the back of the truck and taken to a depot 2 junctions north. The chap in the traveller drove me there and we waited for the truck to arrive. When it was unloaded we decided to have one last go to get him started before I tried ringing for recovery again. He was stumped and checked the air filter to find that the seal was not seated probably and seemed to be a bit too small. After checking all the connections again Eric fired up and seemed to be running well So I then headed off for home, with the green traveller following me up to the Kettering junction to check I was OK.

All went well until 60 miles into the journey and the same problem started again However I slowed down and came off the M11 to take a longer route home and all was well again and I arrived home 6 hours after leaving the rally. So still stumped as to what the problem is. Having looked at simmitc's thread here: http://www.mmoc.org.uk/viewtopic.php?f=4&t=49906 could the badly fitting air filter seal be causing the problem, particularly as it happens under load on motorways?

Thanks very much to everyone who has offered helped so far. Much appreciated, especially to Terry the fireman in the green traveller who spent several hours helping me in the pouring rain and gave me a hi-viz vest to wear when at the side of the road. You were a star (If you're reading this I've ordered a new fuel pump from Bull Motif and it should be delivered to you in the next few days)

[ASL642]

Sorry we couldn't help more. Just glad you got home

[LouiseM]

Thanks Lou, and for the Pimms and cake I was glad to eventually get home but all part of the fun of owning a Minor!

[rayofleamington]

I've had similar issues, but not often - one was fuel starvation caused by fuel pump not working when hot (it wasn't an SU unit).
Maybe the most similar to yours was a carb fault, where the throttle slide was fine when cold, but would stick fully open when hot. This caused over-fueling and loss of power, making the engine stall if you tried to idle. when hot it wouldn't start at all (could tak 45 minutes or more to work again). However when I spotted the issue and manually pushed the throttle slide back down it would start.
Another, but less similar was a partly blocked inline filter - the carb ran empty when under heavy load. Car was fine as soon as it rolled to the side of the road... Along those lines, have had this behaviour also from a car with no inline filer - all the fluff & gunge built up in the needle housing, with same effect as a partly blocked fuel filter.

Problems like this are a pain to diagnose. We had a similar (but different) issue en route through Spain and it only occurred when going along fast A-roads up hill. Usually when passing a truck or some other highly inconvenient moment!
Your issue/symptoms appears to go away by itself just by cooling down.


Rather than randomly changing parts and not knowing if it's fixed until it re-occurs I'd recommend taking a bunch of useful stuff with you to help guide the diagnostics when it is in faulty mode.
The difficult thing is making the car break down near to an area where you can safely play with it!

First thing I'd want would be a spare spark plug - remove #1 lead and sit the plug on top of front head bolt. This way you will see if you're getting a decent periodic spark! It's a much better method than trying to remove an existing plug at max temperature! Seeing the spark in direct sunlight is not easy - you really want to be in the shade, even if that means closing the bonnet most of the way - then you should see a clean blue spark.
*Assuming you have a decent spark move on to fuel...

The fuel pump will stop ticking when the carb is full - most will have a slow background tick as the pressure in the pipe leaks back through the pump (some dont). With ignition off, carefully remove carb end fuel pipe and fit into a small plastic bottle, like a 330ml fizzy drinks bottle, cleaned to remove all sugar residue!. (Be careful! e.g. have some 5L water bottles nearby, and some rags, but if fuel gets on the rags, keep them WELL AWAY FROM YOU & THE CAR!).
With ignition on (only as long as it takes to hear the pump activate), the pump should race away and chuck fuel into the bottle. If that works, that rules out issues with the fuel tank, fuel lines, pump and pump 12v supply.

Then if you're well organised you can put the lid on the bottle and make a very small hole in the lid - with the bottle mostly upside-down you now have a petrol sprayer (be careful! e.g. have some 5L water bottles nearby, and some rags, but if fuel gets on the rags, keep them WELL AWAY FROM YOU & THE CAR!).
With the fuel pipe securely back in place and ensuring the problem is still present, remove the air filter housing. at this point check the throttle slide (even if you know it's ok, as the plop noise is fun) the damper should limit how fast it will rise when pushed with a finger, and it should fall back down rapidly with a 'plop'. If that's working, spray approx 1 to 2 teaspoons worth of fuel into the carb mouth.
If the car now starts and later it stalls, this indicates a fuel issue INSIDE the carb (such as stuck inlet needle)



*If there is no spark, or it's intermittent or weak, then focus on more of the electrics:
Using a bulb test circuit connect from dizzy LT lead/connector (whilst harness is in place) through bulb to ground. With ignition on, turn engine by hand (starting handle) and you should see the bulb go on and off with the points opening/closing.
If this works, and you've already swapped condensor, then more likely issue is in the HT side. however, before removing the bulb test circuit, I'd be tempted to double check the static ignition timing. I struggle to imagine why it would be different when hot, but checking it would make me feel better!


To do all of this at the side of the road isn't fun. It's probably worth a dry run doing the tests to make sure you can, before setting off into the unknown. The last thing you want to do is break down, in readiness to fault-find, and find out your diagnostic gadgets are not up to it!
If you make up some 12v wires with croc clips etc.. for the bulb test circuit, then you could make another (with fuse!) in order to hot-wire the starter solenoid. This is far more efficient than relying on the key when you want to work underbonnet! when over-riding the starter solenoid, do make sure the ignition is on though!! most people have made that mistake at least once

[LouiseM]

Thanks for the suggestions Ray.

After the new fuel pump was fitted the 'fuel into a bottle' test was carried out and all was well, which seems to rule out a problem with the tank, lines and pump.

The problem with doing a 'dry run' to test it is that it has only happened on motorways plus the length of time before the problem starts now seems to have increased. Originally it happened between 5 - 20 miles into a journey, now it seems OK for 60 miles or so. As you say, it would be difficult to try to find somewhere to safely break down, plus it rarely seems to stall when the problem happens - just keeps going but slower.

To recap, the parts that have been replaced are: Coil, condenser, LT lead, HT leads, fuel pump, rotor arm, dizzy cap. The spark plugs look new. The problem has only recently started - when I bought the car it drove 320 miles home, all under load on motorways, with no problem. Is it worth cleaning the carb?

[rayofleamington]

After the new fuel pump was fitted the 'fuel into a bottle' test was carried out and all was well, which seems to rule out a problem with the tank, lines and pump.

Understood. Unfortunately at that point everything was ok anyway. With this kind of really annoying intermittent issue, it's best to re-run the checks when the fault is there.

[LouiseM]

Unfortunately at that point everything was ok anyway.

No, it was carried out when the car wouldn't start. With the old pump on it seemed that no fuel was getting to the carb due to a fault with the pump. The test was then carried out on the new pump to check that the fuel problem had gone, which it had.

[rayofleamington]

ah - my apologies.
In which case, there's a slim chance that the wiring to pump may be the issue. e.g. a high resistance connection that heats up over time. I'd be pretty surprised if that's the case, but changing the pump may have disturbed the connection enough to make it work again.

Have you still got the old pump, and does it appear to work ok when connected up?

[meh]

If it's a heat problem try some freezer spray on various components

[dalebrignall]

sorry to hear your tales of woe louise , after you have changed the fuel pump get the old one referbed and carry a spare in the boot . i would consider going electronic ignition , accuspark , or simon bbc , good systems ive run them on both cars for 10 years and not had a problem honestly its worth the £45

[dalebrignall]

if you go electric it should come with rivitless rotor arm theres a lot of poor qualiaty service parts around . i work on the theory if its in the boot i wont need it .

[LouiseM]

Thanks Dale. Something to consider but I'm not sure that it is an ignition problem

[kennatt]

I had a very similar issue,if I gave it a blast down a dual carriageway,after about 4miles or so it would lose power,checked everything like you and then did the following,ran it hard and fast to create the fault.Then immediately switched off to stop the pump working,put the clutch in and coased to a halt. Got out and unscrewed the top of the carb and found that the fuel level in the bowl was too low,allthough the pump was ok, fitted a new fuel needle and valve.... Problem solved,at gentle cruising the needle was obviously letting enough fuel in to run ok,but not enough for the demand at higher revs, worth a check on yours,It's always worth renewing the needle and valve in anycase if it's the original in the carb,bound to be worn after 20 odd years. good luck

[bmcecosse]

It's certainly not an 'air filter seal'.....oh dear - there was some very poor advice (although I'm sure well intended) along the way. It certainly wasn't the coil - but as long as you bought an 'old' coil - just leave it place. No petrol? The fuel pump would be hammering away pumping air - not just 'not pumping'. I still think you should fit a NEW dizzy as advised a while back - but I now wonder if there is a vacuum developing in the fuel tank - after driving some distance. Initially it struggles for fuel (the rough running..) and then stops. After a while - especially if the filler cap is removed perhaps to add fuel, the vacuum is gone and the car runs fine again. It may even start again after a short time - but with the rough running due to shortage of fuel. Could also be intermittent blockage in the fuel tank - but you have done the 'pint' test and it seemed ok. Quick test for a 'lack of fuel' breakdown is to squirt petrol/carb cleaner (basically anything highly flammable) into the carb - and if it immediately starts and runs for few seconds - it IS a fuel problem. If it still doesn't start - it's an Ignition problem. My money is on vacuum now. So if it happens again - take the cap off and listen for air sucking in... You should also add a USB charging point in the car for the phone......

[rayofleamington]

I now wonder if there is a vacuum developing in the fuel tank - after driving some distance. Initially it struggles for fuel (the rough running..) and then stops.

I would expect that a vacuum in fuel tank is highly unlikely to be this issue, especially as one occurrence was with low fuel.
Fuel vacuum could give a vapoured fuel pump (at this time of year, but less in winter), leading to the pump ticking like mad, not "then stops"

The basic methods I suggested to rule out major junks of hardware should highlight where the issue is. The problem could be in a dozen different places, hence so much shooting in the dark.

[chickenjohn]

-snip-

To recap, the parts that have been replaced are: Coil, condenser, LT lead, HT leads, fuel pump, rotor arm, dizzy cap. The spark plugs look new. The problem has only recently started - when I bought the car it drove 320 miles home, all under load on motorways, with no problem. Is it worth cleaning the carb?

Check the loom connections to the coil! A dodgy spade connector could be the cause of intermittent problems.

Also, the points may look ok, but with modern parts problems might be a good idea to try another set of good known points.