won't start - now intermittent loss of power

[bmcecosse]

I agree Ray - but I think with the 'low fuel' it had driven 60 miles on that occasion before starting to struggle...which would be right for a tank starting off 'half full' of air. It's still my favourite ! But is hard to know from a distance - hence my oft repeated advice to carry a spare complete known good dizzy - and a fuel pump, and so 'big chunks' of possible faulty components can be eliminated very quickly.

[rayofleamington]

changing parts blindly hasn't helped the unlucky Louise so far, hence trying to help by splitting the problem into 3:
1) good spark
2) Fuel supply to carb
3) carb.

[LouiseM]

You might be onto something with the fuel vacuum theory! I replaced the fuel filler cap a while back so could this be the problem? Does the standard Minor filler cap have a vent hole in it?

[bmcecosse]

YES!

[rayofleamington]

So you have a filler cap with no hole?!?
That would be a bad thing.

Nexty long drive you do (e.g. a gallon's worth..) - even without a stalling issue, if you stop and take the fuel cap off, to you get a little hiss when releasing.
If so, that's very much a bad thing on a minor.!

[Biggles1957]

I had what sounds very much like the same problem with an MG Midget - the AA man drilled a tiny hole in the filler pipe just under the rim of the cap to allow air in and it cured the problem straightaway!

[Larryb]

Mechanic did the following and the Moggy starts and runs so much better.

I've ended up replacing the spark plug wires and the ignition coil, which was very weak.

[bmcecosse]

Oh dear - it's NEVER the coil!! 'Weak' spark would be down to a poor condenser... unless of course somehow a 24 volt coil was fitted.....

[moggiethouable]

Have you checked the rubber pipe that connects the vac advance pipe to the carb?
I had an intermittent problem with rough running because of a small split underneath said pipe.
Just a thought and worth a try for a few coppers.

[LouiseM]

Have you checked the rubber pipe that connects the vac advance pipe to the carb?

Checked that today and it seems fine. I changed the filler cap back to the original one and took him out for a good run this afternoon. Running well initially but then started to 'stutter' and lost power again at the same junction of the M11 - about 5 miles from home - when doing around 60mph. The problem lasted for a very short time and as soon as I slowed down to pull off at the junction it started running fine again. Drive him along a nice long straight stretch of the Tour De France route, getting up to 60mph again, but he continued to run fine with no problem. I drove for around 30 miles in all but what I did notice when I got home was that everything was very hot under the bonnet - a lot hotter than usual. The water & oil levels are fine but I noticed that the water in the radiator was very rusty coloured. Could an overheating problem cause the intermittent loss of power?

[aupickup]

possibly could hows the thermostat
or could be partly blocked somewhere or maybe another rad

[bmcecosse]

And when you removed the filler cap - any sign of a vacuum? If it was a hot day - it would be hot under the bonnet. Do you think the engine had 'boiled' ? Overheated engine can of course encourage an attack of 'the vapours' -and could also cause valves to stick open in tight/poorly lubricated guides.. But could also cause valve gaps to close up, causing mis-firing. I suggest check the valve gaps - and set the exhausts to 15 thou.. I actually run mine at 18 thou now (it had been known to misfire when working hard in hot weather) - but then I do have a big valve 940 head on the engine.

[LouiseM]

No sign of a vacuum, and it wasn't a particularly hot day here today. Everything seemed really hot to the touch under the bonnet - rad, top hose, dizzy base, coil, sump. I know things will usually get hot after a run but it seemed unusually 'over hot' if that makes sense.

Re: checking the valve gaps, the workshop manual will be bedtime reading!

[gtt1951]

Louise, if it is that hot, has the water pump failed?
George.

[rayofleamington]

ah - very hot!
I've only had one get so hot that it wouldn't run - and that took total water loss at >70mph for a fair while!

Generally if the cooling water isn't boiling off (with accompanying steam and noises), then you've not got hot enough to stop it from working, but this is only a general rule, and potential overheating needs investigating (blocked rad, missing pump blades, stuck thermostat)

However, timing related issues (heavily retarded) can also cause a very hot head.

[bmcecosse]

Yes indeed - although I've never understood why - retarded ignition does seem to make for a hot engine - some even report glowing red exhaust ! Have you tried advancing it till it 'pinks' Louise - then retard v slightly ??

[gtt1951]

Yes indeed - although I've never understood why - retarded ignition does seem to make for a hot engine - some even report glowing red exhaust !

BMC, I had this happen to me in the early 1970's with a '67 Singer Vogue Estate (1725cc engine). It went in for a service at a Rootes garage in Teddington (near my place of work - still is my place of work) after a trip to Poland, and they set up the dizzy according to the pulley markings, telling me the timing was out a lot. I couldn't understand why the timing should have been out at all.
On the drive home (to NW London), the car ground to a halt. The AA man said everything looked fine, but the exhaust manifold (it was late and dark by this time) was Cherry Red when I stopped!
In the morning, at home, I looked at my engine and found the dizzy was turned through 180 deg !!!!
I put it back where it was supposed to be (set it "by ear" as I had always done) and it purred beautifully. I drove to work and during the lunch-break remonstrated with the garage. Turns out that the crank pulley had been fitted 180 deg out by some previous owner/garage and these plonkers just went by the pulley markings and failed to notice that it was so much more difficult to start and run after their ministrations.
So - manifolds will glow RED if timing is so far out.
Note to Louise - can you run your engine for about 15 mins, at night, and see if the manifold does glow red?

[bmcecosse]

And if it does...post up a picture please Louise !

[LouiseM]

I can give it a go, although prior to the problem starting the dizzy hadn't been touched and the car was running very well, with no signs of the timing being 'out', so I'm not sure that it is due to retarded ignition. When I get the time I'll give the radiator a flush through too and check the thermostat. Thanks for all the help & suggestions

[bmcecosse]

A good flushing can only do good, and by all means check the stat - but they 'never' stick shut...... It is possible I suppose that a 'winter' stat (88 or even 92) has been fitted - great in winter, rubbish in summer.