Mini suddenly sounded/ran like a dog; now won't start

[TVR Sagaris]

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.

[guru_1071]

minis dont have a choke valve as such, when the choke cable is pulled it moves a tiny lever which opens the throttle disc (the bit you can see) if you press the throttle pedal it will open.

are you sure you put the plug leads back on in the right order?

if you did, remove the air filter and pour a tiny bit of petrol into the air intake (about an egg cupful) - this will 'choke' the engine and it should start (or at least splutter a bit)

if you have the tools, its worth doing a compression check - the missing sparkplug tip suggest that somethings not right - its rare for plugs to fail like this.

i would guess that either the head gasket has gone, or its burnt a valve - either of these would allow it to backfire through the carb (but so would fitting the leads in the wrong order)

Edited by guru_1071 on Thursday 30th December 13:21

[TVR Sagaris]

guru_1071 said:

minis dont have a choke valve as such, when the choke cable is pulled it moves a tiny lever which opens the throttle disc (the bit you can see) if you press the throttle pedal it will open.

are you sure you put the plug leads back on in the right order?

if you did, remove the air filter and pour a tiny bit of petrol into the air intake (about an egg cupful) - this will 'choke' the engine and it should start (or at least splutter a bit)

if you have the tools, its worth doing a compression check - the missing sparkplug tip suggest that somethings not right - its rare for plugs to fail like this.

i would guess that either the head gasket has gone, or its burnt a valve - either of these would allow it to backfire through the carb (but so would fitting the leads in the wrong order)

Edited by guru_1071 on Thursday 30th December 13:21

Thanks for the reply, I've got a copy of this thread in the technical section ( http://www.pistonheads.com/gassing/topic.asp?h=0&a... ) where the diagnosis was the same as yours: HGF or burnt out valve.

A friend of my dad's who restores/races classic MGs also thinks it's HGF, so I'm going to get the head off and let him check everything.

That means I need to get a new head gasket, which sounds tricky. My local parts supplier is Moss ( http://www.moss-europe.co.uk/ ) and I'd be interested if anybody has experience of their head gaskets.

[Jon Brown]

I have never used Moss, but any motor factors will be fine.

I just used Payden HG kit for mine (copper), from the local motor factors and seems fine.

Taking the head off is a relitively quick job, just remember to tighten the head to the right torque settings in the right order and check they are tight once the engine is warm. It all explained in the haynes manual.

Hope you sort out your issue

[minivanman]

Before you go pulling the head off, do a compression check and see if its actually your problem!

[TVR Sagaris]

Head gasket was blown between three and four. Everything else was fine, although there are obviously all sorts of small jobs I still need to do - this is a Mini after all.