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MG Midget and Sprite Technical - dying/stalling when at temp, related to clutch?

An intermittent stalling problem that only occurs when up to temperature.

1275 (1969) midget - no modification other than electronic ignition. Was running fine until recently. Also, have managed to get 70mph down duel carriageway in her with no problem, however, the stalling problem was occurring before and has since... So, when she runs fine, she runs really fine!

After running for about 10-15 miles, the engine slows and stalls/dies. This stalling/dying is increased if the accelerator is pressed. Sometimes the stalling is preceded with some popping and the occasional backfire. The car runs fine up until this point. Once stalled, the car won't start for about 5-10 mins, and then will run for a few more miles. Almost like it has to cool down..?

I have also noticed, once at full temperature, but idling on the drive, if i press the clutch (without putting in gear), the revs drop and if i put in gear (clutch still depressed) the engine stalls... But, will idle quite happily in neutral without clutch pressed.

Changing gears has become more crunchy too, and at times very difficult, but can also be quite smooth!! - She's always had this problem, but i think it's getting worse, but it could be my imagination (or wishful thinking in trying to diagnose the fault)

This problem was initially thought to be a fuel starvation problem, but now I'm beginning to think clutch/gear related...?

note - usual checks have been done - oil, fuel, water, electrics

Thanks

Fiona

NB - I'm newby girl at car mechanics, so you may have to give the 'ladybird' version ;-)



F Keates

Fiona nice to have your post.

So to confirm you can be driving along and the engine will lose power and stop after about 15 minutes is this the case?

I am trying to establish if there is any connection with the clutch because I doubt that very much.
Robert (Bob) Midget Turbo

hi,
yes, after about 15 - 20 mins of driving, she'll lose power+ die. Sometimes preceded with coughing, sputtering + occasional back fire. Only noticed today the clutch/gear thing.

f
F Keates

When it dies next time, nip out and remove the petrol tank cap. If there is a rush of air and the engine works properly again, you have solved it. The cap must have a built in air bleed as there is no other way of replacing the fuel you are using with air. So you develop negative pressure in the tank and eventually the pump cannot overcome this. Your symptoms sound like fuel starvation, and the tank cap problem has been a cause of this before. By the time you have let the car sit for 15 minutes I imagine the pressure has equalised again, and so off you go.
Mike Howlett

Clutch and stalling sound like two different things probably best for two threads to sort individually

Clutch - have you checked the level, colour and condition of your clutch fluid?

Have you checked the level and condition of your gearbox oil and know for certain when it was last changed?

Have you got a copy of the owners Handbook, jolly useful (but not for these problems) (ref 0058) - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html

I'm old and had a few cars but I'm still at Ladybird level so I can't give technical reason and explanations but the revs dropping a bit when you put the clutch in happens when things are a bit worn but shouldn't get to stalling

As on another thread here it will be best for you to stick with someone like Bob asking one question at a time and you giving the answer before going on to the next question as trying to diagnose things over a forum is very difficult and there's usually many possible causes to a problem so they need to be eliminated one by one

For an idea of how long and complicated it can get and why you should take it one step at a time see- http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=thread&access=&subject=97&source=T&thread=2011011700524811186
Nigel Atkins


Hello Fiona,

You say the car has electronic ignition. Would that be Optronic by any chance? I had precisely the same symptoms with my car, and eventually diagnosed it as the Optronic optical sensor failing. seems that when they start to fail they're sensitive to heat and work fine when the car is cold.

Try swapping a set of old-fashioned points in temporarily and see if that cures it?


Hope that's of some help?
Mark

PS - there's a thread in the archives describing how I finally diagnosed the problem with the optronic if you're interested...
MarkH1

Hi Mike
Will check the filler cap next time, but fairly certain it's loose.

Hi MarkH1
It's a new Magnatronic. I changed over as a possible solution to the problem. i did think this had sorted it as i managed to run her for 30+ miles and get 70 out of her, with no problem. However, in the mean time, the starter motor packed in (& the battery) and once I'd replaced that & got her running this weekend, the original problem of dying when up to temp has returned. It appears to happen when in gear or being run, rather than when in neutral/idling.


I'm not sure if this makes any difference, but the engine seized since the original fault, causing the starter motor not to work. I took sparks out, but her in gear, rocked her back & forward and freed the engine. Sparks back & she started OK.... (engine oil level is fine, as have changed oil & filter 2 months ago). Will start a new thread on this if it's unrelated.

Clutch & gearbox fluid/oil changed in the summer as she'd stuck in 1st and had to have engine out to free it. (nb tried the high revs and forcing out of gear thing LOTs of times, but didn't work. Gearbox looked ok, with no play or wear on parts when I removed it. Bearing had jumped out, causing the jam, but that's a different story - or thread!). Will check levels though, in case a leak has developed.


The seizing makes me think it's a mechanical (engine/gearbox) type problem rather than fuel or electrics... The dying appears to happen when in gear or being run, rather than neutral/idling. My thoughts being, if when getting to temp & under load, the 'engine'/another mechanical part stops running freely & starts to seize up. Will this cause her to die and then stop until cooled down..? or am I barking up the wrong tree! Nb have checked water pump, temp & radiator - all ok

I've read the thread regarding fuel pump... very interesting as fuel pump was going to be my next thing to look at...

thanks

f
F Keates

oops - correction to last paragraph. should read:

The seizing makes me think it's a mechanical (engine/gearbox) type problem rather than fuel or electrics... My thoughts being, if when getting to temp & under load, the 'engine'/another mechanical part stops running freely & starts to seize up. Will this cause her to die and then stop until cooled down..? or am I barking up the wrong tree! Nb have checked water pump, temp & radiator - all ok
F Keates

Pump thread was more to show how you can go from fuel octane to spark plugs to lots else then fuel pump when problem is probably poor wiring by a previous owner - so a step by step diagnois was needed rather than a spread of ideas

With your additional information someone like Bob may be able to progress further - not me, most mechanical stuff is beyond me and this sounds well passed that (I was thinking clutch)

Good luck, keep the info coming
Nigel Atkins

This BBS forum has a very high record of successful diagnosis of problems, although sometimes it takes a while for the correct answer to be identified! Often the problem is in gaining a sufficiently accurate and precise description of the relevant symptoms. This isn't a dig at anyone - but clearly when those advising cannot actually check the fault directly then reliance must be on the owner and it helps to check things in the right order.

Fiona, from your message, you are not quite so much at the "Ladybird book" stage as you at first implied! I think you are significantly more knowledgeable than that! But when you say the engine seized - do you mean exactly that, or do you mean that the starter motor jammed. Your method of repair sounds more like a jammed starter - now sorted by replacing it. It doesn't really sound like a seized engine to me. But starter and battery going faulty at the same time would make me suspect the engine earthing strap was maybe sub-standard so I would now check that is OK as well.

I cannot really think of any circumstance why pressing the clutch should cause the engine to die - sometimes they will slow a little, but not to the extent of loosing power and dying. I think that is a red herring!

Next time it does this look and see if the tachometer is flicking wildly. This would confirm that it is a fault with the low-tension ignition circuit. I think it is,, but worth checking.

Guy

Hi Guy
Not quite sure of the terminology, but I'm fairly certain it was the engine that jammed/seized as it was a new starter motor. But granted, the starter motor could have just stuck...

Earthing straps - I've changed the one from the battery and there's one that comes from the bottom of the engine round to the wiper motor area & that looks ok. Where else will/should i locate them? Earthing seems to be a common suggestion. Have checked resistance & voltage with multi meter, it appears ok, but I'm not that confident with the meter...

Just to complicate & frustrate matters. Took her out today and filled up with fuel (1/4 full so topped up with super unleaded & additive as per usual). Then took her for a run up & down Ashby bypass, for about 20/25 miles going up to a steady 50/60 mph - all running wonderfully!!!!!!! No coughing, dying, backfiring, loss of power, anything (some crunching of gears, but that seemed to ease). Grrrrr.

So, what is different to today than yesterday or Friday?? Is there now an 'R' in the month or an earthquake in Anglesey? Or just an intermittent blip and she says, 'Yep, I'll work today'...? - I jest :) It could be that it's colder today and so wanted running longer before the problem reasserts its self. Or could it be something to do with the full tank of fuel? - she does have a new fuel filter so unlikely to be drawing in sludge from bottom of the tank..? but will take advice.

I'm now beginning to think the clutch thing is a red herring/something different.

Going to borrow an ignition coil and run her tomorrow until the problem re-occurs...

Tell me about the 'tachometer'?

NB revs & oil pressure all normal.

Please keep suggestions coming & I'll keep you posted.

ta
f
F Keates

You are too kind Nigel but just love helping with logic.

Yes I agree with Guy you appear to be describing a jammed starter motor which would be totally unconnected with the dying issue.

What I would like to ask is along with Guy and the tacho

When the car loses power does the engine simply die (stops firing) or does it begin to faulter. You mentioned popping and backfiring, these are typical symptoms of fuel problems. But as Guy dscribes if at that point the tacho jumps around it would suggest the problem was electrical

Robert (Bob) Midget Turbo

Fiona,

I see you are going to try another ignition coil. I was going to suggest that because a poor coil can mimic fuel starvation.

Charley
C R Huff

Hi Fiona,

The rev counter can give a very useful early stage in the diagnosis. The rev counter is triggered by the low voltage side of the ignition circuit. That is, ignition switch, coil, electronic ignition module (or normally points, but you have already changed from these) and all of the interconnecting wiring. If there is a fault with any of this it will almost certainly show up as a wild flickering of the rev counter needle when you feel the engine beginning to fail. It is the first thing anyone should look at when their car begins to die!

If the needle falls steadily it is most likely to be a fuel related fault. If it jumps around as the revs drop then it certainly suggests an electrical fault. Its a really important first diagnosis step that can avoid you wasting time (and money) chasing wild geese, red herrings and hares all over the place!
Guy

if this is a 2 part differant issues.

could the clutch part of the problem be a result of wornout thrust bearings/washers in the engine and just masking the noise to the tranny bellhousing?

Unlikely I know, as its rare for the thrust washers to wearout on a 1275, But....


Prop
Prop

Credit where credit is due Bob (and Guy)

And Prop is on my level of bad written descriptions - I did mean the clutch as a seperate issue - on my (prevoius) 1275 box and clutch the revs dipped with the clutch pedal down

Wont even mention rolled mat in a Spridget forum

But all that's off subject now

My only (s/h) experience of a faulty coil was a drop in engine power (so could come back when cool) but as with other thread could also be coil lead or fuel problem, or, and so on

So stick with the "lads" B & G (did you see what I did there)
Nigel Atkins

On the fuel front another possible cause that can happen when hot is fuel evaporation. Is the heat shield in place?

Trev
T Mason

Please check and change the oil in your gearbox as it sounds like it is needing topped up
rachmacb

hi folks

Many thanks for your suggestions - greatly appreciated.

I have run her today for excess of 50 miles at various speeds on open road & through town. Not a single problem! and yet, i haven't done anything...

When the problem does occur, the rev counter slowly dies. The engine falters (judders, misfires, coughs & occasionally backfires) and slowly dies, the speed of dying is increased if i press the accelerator.

The initial thoughts were fuel starvation or electrical, so i think the clutch thing is a separate issue - the clutch was checked, and gearbox oil changed when i removed the engine in the summer. It did have some life left in it, but I'm now of the opinion it probably needs replacing/looking at :( . Will let you know how i get on in a separate thread. I'll keep this one for the stalling issue.

Fuel vaporisation is a possibility; however, nothing has changed with the fuel line location or heat guard before and since the problem showed itself. So I'm inclined to think unlikely, but it is a possibility if all else fails as i'm aware Midgets can be prone to this.

I'm going down the coil route first (carrying a spare for when the problem next occurs as that's easy) and will also check for vacuum in the fuel tank/filler cap. I'll also see if she picks up if i put her in neutral/dip clutch - this would indicate a fuel supply/pump problem as it would allow the fuel supply to catch up with demand/demand to slow down to fuel supply rate. Does this sound reasonable..?

I'll keep you posted... big drive on Friday to see what happens - hoping for good weather to go topless!! ;)

cheers

f
F Keates

Sounds great... just an add-on comment.

go back and re-read the help for using the tach reading (when/as) the engine dies next to determine if its fuel or electrical

Thats a great test,,, easy and simply, and will save many hours of head scratching

intermitten prolems can drive one to insanity
Prop

Fiona,
Have you checked the valve clearances recently? Tight valves can cause the engine to feel like its beginning to seize, and this happens under load and with the engine hot. Better that valves are slightly slack rather than too tight.

Hmm, come to think of it you said the engine cut out completely so this then isn't likely to be the fault. But may still be worth checking them.

Guy
Guy

This thread was discussed between 14/02/2011 and 16/02/2011

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