sooty plug- just the one!!??

[mu0u207b]

HELP- ive been having a problem with my minor for bot 12 months and cannot seem to sort it. My problem is that my no. 3 plug keeps on sooting up wilst 1,2,and 4 are greyish tanned. This eventually leads up to carbon build up and running on and pinking. I have changed the cylinder head, rocker gear and most of the cooling stuff- pump and radiator. The car has been modified with a HIF38 carb and water heated manifold and servo brakes. This has not been a problem since fitting these items. the servo was fitted 9 months ago and the carbie about 18 months ago. The problem has been present for about 12 months. Would the carb if worn lead to the varied condition of the plugs. Obviously some plugs are running weak whereas other are running rich??!! Ive have tuned the mixture setting on no. 1 plug with that gunsens plug thingy. Could it be a cam shaft problem i.e worn cams or followers. Please help because this has got me stumped.

[Willie]

Well, you have the perfect tool to check for this problem if you
have a Gunsens Colourtune. With the mixture set to what appears
generally ok it is necessary to check EVERY cylinder with the colourtune
and you should see a marked difference in the colour of the explosion
in the chamber which is producing the sooty plug. You should aim for
a colour of light blue in each chamber. By the sound of it you should
find that the 'faulty' chamber will be orange in colour when the other
three are light blue. The 'sooty' condition suggests either too rich or
too much oil in that particular chamber.

[bmcecosse]

Could be worn or broken rings on that cylinder - best to get a compession test.

[newagetraveller]

EITHER there is no spark at this particular spark plug. This could be due either to a faulty spark plug or a fault in the distributor cap or HT lead going to the plug.

OR there is something wrong with the number three piston that is allowing oil to get into the chamber. It could be faulty piston rings or a hole in the piston.

If the plug smells of petrol I would suggest the first. If it smells of oil I would suggest the second.

[mini_chrisls]

I've tryed everything, and was wondnering if anyone here could help.

Ok, not a morris minor, but I've got an a series in my mini, so I can't imagine it's too different.

My plug on my third cylinder keeps getting very sooty, like it's running very rich. Eventually it'll drop down to running on 3 cylinders. The other plugs are as they should be.

This is what I've tried so far...

Compression test, everything is fine all cylinders 150 - 160 psi
changed head gasket, head skimmed, new valve seals, valves re lapped
points gap re adjusted
running without air filter
all sorts of misture settings
swapping over spark plugs and HT leads, new spark plugs
rotating dizzy cap 180 degrees
adjusting valve clearences

With the plug cleaned up and sitting on the block it sparks away hapily.

The points, condensor, HT leads, plugs, air filter, etc... have all just been replaced.rotor arm swapped for t he origonal but no joy.

Any ideas what to try next?

[Alec]

Hello MC,

if it is dry and sooty, it is not really an oil problem, but an excess of fuel or a dearth of air. As it is number three, it is unlikely to be a blockage in the exhaust manifold as that would affect number two also, and the inlet manifold feeds three and four so I would check the lift of the cam lobes on number three cylinder (Seeing as you have changed the head)

Alec

[mini_chrisls]

Do you mean actually taking the cam out inspection it? It's the same angine head. It has been skimmed though. But the problems were there before i did this. I was just hpoing it might cure the problems. but it hasn't so far.

The valves seem to open and close when you turn the engine over by pushing it in gear.


Oh, and I've tried adjusting the valve clearences, so the clearences on cylinder 3 are smaller, giving the valves more lift, more time open, open further, etc. and increasing the clearence slightly on the other cylinders as this helped someone with a similar problem, but not me.


Thanks for the help Alec.

[Willie]

The Only time I have had anything similar to this problem was down to the
wrong plugs for the engines state of tune.

[mini_chrisls]

I've tried two different sets of plugs. I can't imagine why it would only foul up the plug in the third cylinder though. hmm...

[mkwc]

When you changed the manifold did you change the gasket at the same time, if so did you replace the two sealing rings between head and manifold.
it sounds like 1 cylinder is running rich and the other 3 are running lean. Check for air leaks with a petroleum based airosol can (wd40, or fly spray) by spraying all the inlet joints with the engine running (carefully) if the engine speeds up then you have found the leak.
If this fails then I would go up 1 heat range in no 3 cylinder spark plug.

Regards Mark

[bmcecosse]

Sounds like you have checked everything normal - it could be worn camshaft. Even though the comps are ok - you could have a broken oil ring in that cylinder - does it burn much oil ? You will need to turn it over by hand and measure the actual lift on the valves - a good steel rule will be ok for this. If it's substantially different on that cylinder compared to others then problem solved. If it's an 850/ 998/1098 you can change the cam in the car - 1275 needs engine out - unless it's a genuine S unit !! Maybe just wrong grade of plugs - what you using ?
And join up to MINIFINITY.COM for excellent Mini advice - you will notice I have both Minor and Mini !!

[mini_chrisls]

I've had enough. It's going to a garage when I find one which will have a look at him.

Here is my long, involved thread on minifinity...

http://www.minifinity.com/index.php?nam ... ic&t=33469

Everyone has tried so hard to help out, and I'd just like to say thank you for all your help and suggestions, but I've decided that whilst I've still got 3 cylinders I should try find a garage to fix it. if they can!

thanks all, chris.

[Alec]

Hello chris,

quite a saga, you didn't mention plug fouling though, the NGK BP9 is equivelant to a Champion N9Y etc. in heat range, and is, I think correct for your engine.
From my point of view, I would not take it to a garage and say I have a problem, fix it! That could be very expensive unless you know of a good, reliable one. (My feelings on modern garages are that they like to change assemblies and not really do proper diagnoses) Certainly it would be worth, if you have lost all patience, to take it for an electronic tune up and see the results of that.

Alec

[bmcecosse]

Ah yes - I remember the thread chrisis ! I answered it a couple of times (royallingham - i use my real name on there!). It really sounds like you have broken oil rings in that cylinder - by luck the compression rings are still ok, hence the good compression. I suggest you look for another engine because 998s are just not worth fixing. There are often some going FREE, or for very little money - check 'finity For Sale, and ebay. You could always upgrade to 1275! If you take it to a garage it will cost an absolute FORTUNE!

[mini_chrisls]

So, the rings could be letting oil into the cylinders, but holding firm when they are pressurised from the other side, ie, during a compression test.

Ah, well, this is just getting worse, I dunno when I'll finaly be able to start driving, hopefully before the summer. I'll start looking for an engine then....

[Skeggysteve]

mini chrisis,

Agree with bmc any 'modern' garage will not really be able to help, just charge you a fortune.

Where about are you?

If you are near to Skegness come along I have a Crypton machine and the instruction to work it. Long story but the v6 in my Scimitar now runs on 6 cylinders!

Steve

[Alec]

Hello BmcE,

the fact that there are engines for very little money doesn't mean that you will get a good one, I would have thought quite the reverse.
I always prefer the philosophy of better the devil you know.
I would most certainly pull the piston and check it; if the bores are not overly worn then a new set of rings may do the trick.

Alec

[bmcecosse]

But it's easier to grab a cheap engine - and overhaul that if it needs doing! Then it's just a swop into the car in one day. Engine I picked up a while back was like new inside! It had been 'little old lady' car - car had rusted away to nothing, but all the mechanicals are unworn.

[mini_chrisls]

Roy, you might know Carl (Brumski)? On minifinity, well he has a few options about engine which I'll discus with him.

In the mean time, I won't be driving it. Considering once started on 4 cylinders it will continue on 4, do you reckon pre heating the spark plug with a blow torch might get it running on all four? I'll try spraying WD40 on the joints, but I can't imagine it will do anything, as I've changed the head gasket since problems comenced so the manifold gasket is new and tightened up.

[mu0u207b]

Hey guys. i believe that i finally sorted out my single sooty plug. Well i had changed vertually everything, new rings, bores seemed ok and within tolerance, new cylinder head, rocker assembly. After spendin a good fortune in one go on new bits, i did a couple of miles on the new bits before inspecting the plug. Inspected it, guess what STILL sooty. It wasnt until i tightened down the head nuts a bit more that the sooty plug went. I think my problem was a dodgy seal somewhere where compression was venting very slightly to give an unballanced mixture. When the engine next out i will have to get the block skimmed as its starting to get darker again.