Mini suddenly sounded/ran like a dog; now won't start
Discussion
A couple of days ago, my Mini (a 1990, 998cc 'Checkmate') suddenly sounded absolutely awful - literally like a bag of spanners. It sounded like it was misfiring but there was also a loud clatter. This was accompanied by a severe drop in power: it took full throttle to move off and the car struggled to accelerate.
Under the bonnet, there was a sort of gunshot noise coming from the carb/inlet manifold area when on the throttle. I took the dashpot cover off the carb to check it and clean it. Everything seemed fine; the needle was fine, and it wasn't particularly mucky. I put it back on and the car took several attempts to start. When it did start, it still sounded like it had a terrible misfire and there was still a clatter, although it wasn't as bad as it had been.
I checked the plugs and, on the third one along from the flywheel end of the engine, found that the central electrode had gone:
Replacing that plug made no obvious difference.
Today, the car refuses to start. The plugs are sparking and there is fuel in the carb. It turns over and occasionally starts to fire up but never quite does. My dad suggested squirting Easystart into the carb to check if it was a fuelling issue. I took the air filter off and found the choke butterfly valve stuck in the closed position - i.e. so no air can get in. The choke cable still works normally but the valve doesn't move, and I can't seem move it with my finger.
My plugs look okay - apart from the one above - but are not wet.
So I have several questions.
Initially, I suspected that the problem was headgasket failure. This now seems less likely: I assume HGF would not prevent the car from starting, the radiator header tank had coolant in, it wasn't particularly low on oil and both coolant and oil seemed fine, apart from the coolant being a little bit brown.
Does anyone have any idea what has happened to that spark plug? And, more importantly, what sort of damage would that bit of it do to the engine? Might it have made a horrible noise if it was inside the cylinder?
Why won't the car start? And what's going on with my choke valve?
Any help greatly appreciated - I'm supposed to be using the car on Friday.
Under the bonnet, there was a sort of gunshot noise coming from the carb/inlet manifold area when on the throttle. I took the dashpot cover off the carb to check it and clean it. Everything seemed fine; the needle was fine, and it wasn't particularly mucky. I put it back on and the car took several attempts to start. When it did start, it still sounded like it had a terrible misfire and there was still a clatter, although it wasn't as bad as it had been.
I checked the plugs and, on the third one along from the flywheel end of the engine, found that the central electrode had gone:
Replacing that plug made no obvious difference.
Today, the car refuses to start. The plugs are sparking and there is fuel in the carb. It turns over and occasionally starts to fire up but never quite does. My dad suggested squirting Easystart into the carb to check if it was a fuelling issue. I took the air filter off and found the choke butterfly valve stuck in the closed position - i.e. so no air can get in. The choke cable still works normally but the valve doesn't move, and I can't seem move it with my finger.
My plugs look okay - apart from the one above - but are not wet.
So I have several questions.
Initially, I suspected that the problem was headgasket failure. This now seems less likely: I assume HGF would not prevent the car from starting, the radiator header tank had coolant in, it wasn't particularly low on oil and both coolant and oil seemed fine, apart from the coolant being a little bit brown.
Does anyone have any idea what has happened to that spark plug? And, more importantly, what sort of damage would that bit of it do to the engine? Might it have made a horrible noise if it was inside the cylinder?
Why won't the car start? And what's going on with my choke valve?
Any help greatly appreciated - I'm supposed to be using the car on Friday.
Did you get the electrode out of the cylinder? Could it be that it's scored the cylinder wall and you've got no compression on one cylinder? Mind you, would still start. How's the cambelt? Is it firing at all or just turning over? Turning over faster than usual? (Indicates no compression and possible loss of cam timing...)
NiceCupOfTea said:
Did you get the electrode out of the cylinder? Could it be that it's scored the cylinder wall and you've got no compression on one cylinder? Mind you, would still start. How's the cambelt? Is it firing at all or just turning over? Turning over faster than usual? (Indicates no compression and possible loss of cam timing...)
Don't know how I would get the electrode out without taking the head off, and I'm reluctant to take the head off. I'm hoping it just went in without doing any damage and then went straight out of the exhaust.Most of the time it just turns over, but will occasionally start to fire. I don't think it's turning over any faster or slower than usual.
TVR Sagaris said:
Mini (a 1990, 998cc 'Checkmate').....
... I took the air filter off and found the choke butterfly valve stuck in the closed position - i.e. so no air can get in. The choke cable still works normally but the valve doesn't move,
I think you'll need to replace the SU carb if you want the butterfly to move with the choke cable!... I took the air filter off and found the choke butterfly valve stuck in the closed position - i.e. so no air can get in. The choke cable still works normally but the valve doesn't move,
Shouldn't be too much of a problem because the carb will be coming off anyway so you can remove the cylinder head and fix the burned valves.
Get the piston in question at TDC and use one of those magnets on a telescopic stick, or something long with some gaffer tape on the end to pick it up at a pinch (but don't lose it in there for God's sake!).
If I read it correctly it ran correctly, then misfired because of the plug not firing, and now won't start at all even with a new plug. It does suggest that some damage has happened somewhere... But then, damage to one cylinder isn't going to stop it starting altogether is it? Could it be that the electrode got jammed as a valve closed and somehow jumped the cambelt or broke it?? Just thinking out loud...
How was the plug apart from that? Did it fail as a result of getting too hot for example, or just bad manufacture? If you leave the new plug out of the cylinder head are you getting a spark?
If I read it correctly it ran correctly, then misfired because of the plug not firing, and now won't start at all even with a new plug. It does suggest that some damage has happened somewhere... But then, damage to one cylinder isn't going to stop it starting altogether is it? Could it be that the electrode got jammed as a valve closed and somehow jumped the cambelt or broke it?? Just thinking out loud...
How was the plug apart from that? Did it fail as a result of getting too hot for example, or just bad manufacture? If you leave the new plug out of the cylinder head are you getting a spark?
Cambelt? Yeah it'll be a combination of the 'choke' butterfly not moving and a cambelt problem. Now i'm off to shoot myself in the head. No need for anyone to worry. Just like the cow in the Restaurant at the End Of The Universe I promise to be very humane and hopefully I won't suffer at all. In any event it has to be better than more of this.
Pumaracing said:
Cambelt? Yeah it'll be a combination of the 'choke' butterfly not moving and a cambelt problem. Now i'm off to shoot myself in the head. No need for anyone to worry. Just like the cow in the Restaurant at the End Of The Universe I promise to be very humane and hopefully I won't suffer at all. In any event it has to be better than more of this.
Just trying to come up with some suggestions of things to check without the head needing to come off.Cambelt failure would explain it not firing if that is indeed the case (not sure the OP has confirmed), and just wondered out loud if a foreign body in the way of the valves could cause a cambelt to break or jump.
Would burned valves in one cylinder stop the engine starting at all? In my experience it would start but run like s
t.NiceCupOfTea said:
Pumaracing said:
Cambelt? Yeah it'll be a combination of the 'choke' butterfly not moving and a cambelt problem. Now i'm off to shoot myself in the head. No need for anyone to worry. Just like the cow in the Restaurant at the End Of The Universe I promise to be very humane and hopefully I won't suffer at all. In any event it has to be better than more of this.
Just trying to come up with some suggestions of things to check without the head needing to come off.Cambelt failure would explain it not firing if that is indeed the case (not sure the OP has confirmed), and just wondered out loud if a foreign body in the way of the valves could cause a cambelt to break or jump.
Would burned valves in one cylinder stop the engine starting at all? In my experience it would start but run like s
t.I forgot to say in my main post that I've had the rocker cover off and the rockers were operating the valves normally.
I also forgot to say that the points look fine.
The engine turns over at the key and sometimes sounds like it's starting up properly but then never does. I realise that's a pretty poor description but I'm not sure how to word it better.
The other plugs seem fine - they're the "coffee brown" colour that they're apparently supposed to be - although they are not wet.
Should I assume that at least one of the issues is HGF?
I also forgot to say that the points look fine.
The engine turns over at the key and sometimes sounds like it's starting up properly but then never does. I realise that's a pretty poor description but I'm not sure how to word it better.
The other plugs seem fine - they're the "coffee brown" colour that they're apparently supposed to be - although they are not wet.
Should I assume that at least one of the issues is HGF?
TVR Sagaris said:
I forgot to say in my main post that I've had the rocker cover off and the rockers were operating the valves normally.
I also forgot to say that the points look fine.
The engine turns over at the key and sometimes sounds like it's starting up properly but then never does. I realise that's a pretty poor description but I'm not sure how to word it better.
The other plugs seem fine - they're the "coffee brown" colour that they're apparently supposed to be - although they are not wet.
Should I assume that at least one of the issues is HGF?
Yes, I think it's likely to be the only problem, but check the compressions first,I also forgot to say that the points look fine.
The engine turns over at the key and sometimes sounds like it's starting up properly but then never does. I realise that's a pretty poor description but I'm not sure how to word it better.
The other plugs seem fine - they're the "coffee brown" colour that they're apparently supposed to be - although they are not wet.
Should I assume that at least one of the issues is HGF?
if any are low, the head will have to come of anyway.
I am concerned that there is still a small but deadly lump of spark plug lurking around inside the cylinder 
I can't see a magnet getting it out either
For safety's sake (engine safety not H&S Bullshine) I'd advise head off at the very least so the walls can be checked and the piston surface
After looking at the points did you examine inside the dissy cap, often get a white slimey build up in here that can cause tracking and a bang inside the wrong cylinder. The explosion from that is a familiar cause of the throttle disc getting jammed inside the venturi.
It can be freed off gently if its not to deeply stuck inside the venturi wall, with a tap from a screwdriver gently administered at the lower edge of the disc (the deepest edge into the venturi tube, where there may be a slight step in the passage after many years of running)
As a confirmed A series lover I hope you can soon get it running
bill
edit as usual for spollink
I can't see a magnet getting it out either
For safety's sake (engine safety not H&S Bullshine) I'd advise head off at the very least so the walls can be checked and the piston surface
After looking at the points did you examine inside the dissy cap, often get a white slimey build up in here that can cause tracking and a bang inside the wrong cylinder. The explosion from that is a familiar cause of the throttle disc getting jammed inside the venturi.
It can be freed off gently if its not to deeply stuck inside the venturi wall, with a tap from a screwdriver gently administered at the lower edge of the disc (the deepest edge into the venturi tube, where there may be a slight step in the passage after many years of running)
As a confirmed A series lover I hope you can soon get it running
bill
edit as usual for spollink
Edited by perdu on Wednesday 29th December 22:08
perdu said:
I am concerned that there is still a small but deadly lump of spark plug lurking around inside the cylinder
I can't see a magnet getting it out either
For safety's sake (engine safety not H&S Bullshine) I'd advise head off at the very least so the walls can be checked and the piston surface
After looking at the ponts did you examine inside the dissy cap, often get a white slimey build up in here that can cause tracking and a bang inside the wrong cylinder. The explosion from that is a familiar cause of the throttle disc getting jammed inside the venturi.
It can be freed off gently if its not to deeply stuck inside the venturi wall, with a tap from a screwdriver gently administered at the lower edge of the disc (the deepest edge into the venturi tube, where there may be a slight step in the passage after many years of running)
As a confirmed A series lover I hope you can soon get it running
bill
The centre electrode is more likely to have burnt away rather than broken off.I can't see a magnet getting it out either
For safety's sake (engine safety not H&S Bullshine) I'd advise head off at the very least so the walls can be checked and the piston surface
After looking at the ponts did you examine inside the dissy cap, often get a white slimey build up in here that can cause tracking and a bang inside the wrong cylinder. The explosion from that is a familiar cause of the throttle disc getting jammed inside the venturi.
It can be freed off gently if its not to deeply stuck inside the venturi wall, with a tap from a screwdriver gently administered at the lower edge of the disc (the deepest edge into the venturi tube, where there may be a slight step in the passage after many years of running)
As a confirmed A series lover I hope you can soon get it running
bill
Well I did it. I dug out my grandad's old service revolver and euthanised myself with a carefully placed shot to the head. There was no pain, just a brief burst of light and then everything went black. Pulse and respiration appeared to cease immediately and now all that's left is a faint residual ability to type plus, to my astonishment, a continuing sense of peevishness which I am hoping will soon disappear. I know I'm going to regret this but while some electrical activity still remains in those parts of my brain which aren't splattered across the lounge wall...
1) An SU carb doesn't have a choke butterfly! However if you get an older brother or sister to waggle the pedal to the right of the brake one while you look at the carb there will hopefully be one of those lightbulb moments shortly thereafter.
2) Nor does the engine have a cambelt.
3) The gunfire noise from the carb is because the burned out inlet valve on No 2 cylinder is sending gobs of high pressure gas back up the inlet manifold when the throttle is open.
4) The engine has siamesed inlet ports so whereas a conventional 4 pot would still start and run, of a fashion, with one inlet valve burned out a siamese port engine will affect the adjacent cylinder too and struggle to run at all on only the remaining two good pots.
5) The symptoms couldn't possibly be caused by head gasket failure, except as a by product of the main problem.
6) Why do people never do a compression test as the first step in any engine diagnosis and will me bhing about it for the rest of my life make any difference to this?
http://www.pumaracing.co.uk/diagnose.htm
Now I'm off to see if a second bullet will do anything about the peevishness which is still not fading.
1) An SU carb doesn't have a choke butterfly! However if you get an older brother or sister to waggle the pedal to the right of the brake one while you look at the carb there will hopefully be one of those lightbulb moments shortly thereafter.
2) Nor does the engine have a cambelt.
3) The gunfire noise from the carb is because the burned out inlet valve on No 2 cylinder is sending gobs of high pressure gas back up the inlet manifold when the throttle is open.
4) The engine has siamesed inlet ports so whereas a conventional 4 pot would still start and run, of a fashion, with one inlet valve burned out a siamese port engine will affect the adjacent cylinder too and struggle to run at all on only the remaining two good pots.
5) The symptoms couldn't possibly be caused by head gasket failure, except as a by product of the main problem.
6) Why do people never do a compression test as the first step in any engine diagnosis and will me b
hing about it for the rest of my life make any difference to this?http://www.pumaracing.co.uk/diagnose.htm
Now I'm off to see if a second bullet will do anything about the peevishness which is still not fading.
Pumaracing said:
Well I did it. I dug out my grandad's old service revolver and euthanised myself with a carefully placed shot to the head. There was no pain, just a brief burst of light and then everything went black. Pulse and respiration appeared to cease immediately and now all that's left is a faint residual ability to type plus, to my astonishment, a continuing sense of peevishness which I am hoping will soon disappear. I know I'm going to regret this but while some electrical activity still remains in those parts of my brain which aren't splattered across the lounge wall...
1) An SU carb doesn't have a choke butterfly! However if you get an older brother or sister to waggle the pedal to the right of the brake one while you look at the carb there will hopefully be one of those lightbulb moments shortly thereafter.
2) Nor does the engine have a cambelt.
3) The gunfire noise from the carb is because the burned out inlet valve on No 2 cylinder is sending gobs of high pressure gas back up the inlet manifold when the throttle is open.
4) The engine has siamesed inlet ports so whereas a conventional 4 pot would still start and run, of a fashion, with one inlet valve burned out a siamese port engine will affect the adjacent cylinder too and struggle to run at all on only the remaining two good pots.
5) The symptoms couldn't possibly be caused by head gasket failure, except as a by product of the main problem.
6) Why do people never do a compression test as the first step in any engine diagnosis and will me bhing about it for the rest of my life make any difference to this?
http://www.pumaracing.co.uk/diagnose.htm
Now I'm off to see if a second bullet will do anything about the peevishness which is still not fading.
I don't have a compression tester or know someone who could bring one to me very easily. Both my mechanics are off for Christmas. I will get a compression test done as soon as I can.1) An SU carb doesn't have a choke butterfly! However if you get an older brother or sister to waggle the pedal to the right of the brake one while you look at the carb there will hopefully be one of those lightbulb moments shortly thereafter.
2) Nor does the engine have a cambelt.
3) The gunfire noise from the carb is because the burned out inlet valve on No 2 cylinder is sending gobs of high pressure gas back up the inlet manifold when the throttle is open.
4) The engine has siamesed inlet ports so whereas a conventional 4 pot would still start and run, of a fashion, with one inlet valve burned out a siamese port engine will affect the adjacent cylinder too and struggle to run at all on only the remaining two good pots.
5) The symptoms couldn't possibly be caused by head gasket failure, except as a by product of the main problem.
6) Why do people never do a compression test as the first step in any engine diagnosis and will me b
hing about it for the rest of my life make any difference to this?http://www.pumaracing.co.uk/diagnose.htm
Now I'm off to see if a second bullet will do anything about the peevishness which is still not fading.
The carb has a valve at the back and a valve at the front, shirley? The one at the front, the throttle, - between the carb and the inlet manifold - is opening and closing as it always has. The one at the back - between the air filter and the carb - does not seem to open. How is it supposed to work?
EDIT: another forum suggests otherwise. What actually opens to let air in then, and what can I feel at the back of the carb? I can't find a decent image.
I don't understand why it would run last night but not today. I haven't done anything to it.
Edited by TVR Sagaris on Wednesday 29th December 22:54
Sorry for the bum steer on the cambelt - I have no experience of the A/A+
pumaracing, I am sorry if I have offended you with my stabs in the dark, just trying to come up with things that the OP may not have thought of. If I've misread you then I apologise, but there's no need for the attitude. If I was in the OP's position I would appreciate any ideas that might help.
Will bow out now and leave to the experts. Good luck OP, hope it's not too bad...
pumaracing, I am sorry if I have offended you with my stabs in the dark, just trying to come up with things that the OP may not have thought of. If I've misread you then I apologise, but there's no need for the attitude. If I was in the OP's position I would appreciate any ideas that might help.
Will bow out now and leave to the experts. Good luck OP, hope it's not too bad...
An SU carb only has one "flap" in the air stream, the throttle
the "choke" as we know it for starting the car on an SU is an enrichment device that either lowers the main jet in early SUs or in later ones opening a rotary valve inside the carb body that dumps extra fuel downstream of the mainjet
The only other obstruction on an SU is the cylindrical slide that raises and lowers the metering needle under the influence of lowering manifold air pressure under engine cranking
If the engine isn't running it won't move and might look like an obstruction of sorts. Your finger should be able to lift the slide up into the "dashpot" then you might see the throttle flap downstream, which operates when the cable moves it
For such a brilliant design the poor old SU is often sadly misunderstood
And it IS STILL possible for the centre electrode to drop metal down into the hole, even if it may be rare
the "choke" as we know it for starting the car on an SU is an enrichment device that either lowers the main jet in early SUs or in later ones opening a rotary valve inside the carb body that dumps extra fuel downstream of the mainjet
The only other obstruction on an SU is the cylindrical slide that raises and lowers the metering needle under the influence of lowering manifold air pressure under engine cranking
If the engine isn't running it won't move and might look like an obstruction of sorts. Your finger should be able to lift the slide up into the "dashpot" then you might see the throttle flap downstream, which operates when the cable moves it
For such a brilliant design the poor old SU is often sadly misunderstood
And it IS STILL possible for the centre electrode to drop metal down into the hole, even if it may be rare
Pumaracing may well be right that it's an inlet valve, but my money is still on the head gasket.
A gasket blown between two cylinders will indeed cause these symptoms because of burning gases being transfered from one cylinder to the other (I've seen this on several occasions).
As you don't have access to a comp tester at present, remove the plug from the cylinder where one was burnt out and make sure the plug lead is well away from the area.
Then, with a fire extinguisher handy, get someome to try and start it, if it's the gasket it should start but you will see exhaust gases coming from the plug hole {it should also start if it's a valve, but no exhaust gases) either way, it's head off time.
A gasket blown between two cylinders will indeed cause these symptoms because of burning gases being transfered from one cylinder to the other (I've seen this on several occasions).
As you don't have access to a comp tester at present, remove the plug from the cylinder where one was burnt out and make sure the plug lead is well away from the area.
Then, with a fire extinguisher handy, get someome to try and start it, if it's the gasket it should start but you will see exhaust gases coming from the plug hole {it should also start if it's a valve, but no exhaust gases) either way, it's head off time.
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