11 replies to this topic

[nicknicknick]

Hello,

Been having some major issues with my mini, mostly with very bad hessitation before acceleration!
Before it was managable, but now the engine cuts out.

While slowing building up the revs suddenly smoke came out from where the air filter box attaches to the carbourettor (air filter box was off at this moment), then it was ok. but then it did it again (after about 5seconds) and the engine cut out. Wasn't a huge amount of smoke, but enough to know it definatly shouldn't be doing that.

Any of you guys and gals know what the problem could be??

EDIT:
OK, with a bit of research I think the white smoke is from the engine burning oil. So I think it's the piston rings or the valve seals.
Are there any checks to test these?

Edited by nicknicknick, 12 July 2009 - 01:40 PM.

[jaydee]

remove dashpot and piston and see if its all full of fuel around the jet, that means you carbs overfuelling mate.

[bmcecosse]

Take the oil filler cap off with engine hot and idling - is there a cloud of smoke /fume coming out ?? If so - engine is seriously worn.

[nicknicknick]

Take the oil filler cap off with engine hot and idling - is there a cloud of smoke /fume coming out ?? If so - engine is seriously worn.

Well it was looking ok as there wasn't any smoke from the oil cap.

But then just started it up, then when i switched the ignition off there was a loud bang and smoke came from the air filter part and the oil cap

It's a big job to sort this out isn't it? any recommendations?

[Stevie W]

Hi,

Are you sure the mixture is right and not far too weak?

Usually an engine that has to have the revs built up slowly is running seriously weak and a weak mixture will cause backfires through the carb. Does it run on when you switch the ignition off?

Before you can judge the state of the rest of the engine (worn rings/valves etc) you need to get mixture and timing adjusted correctly.

If the hesitation during acceleration has got so bad the engine stalls now it seems like an you may have an air leak in the induction system somewhere. It'll be worth checking the carb is not loose on the inlet manifold and that any breather pipes attached to the base of the carb have not come loose or perished causing a large air leak. Also check the throttle spindle for wear as this can also cause air leaks and weak mixtures.

Also check the carb for a partially blocked jet and make sure it isn't leaking fuel anywhere.

If the engine does not blow blue smoke out the exhaust either on acceleration or on the overrun then the rings and valve guide seals are likely to be ok. As already mentioned though if you are seeing blue smoke out of the oil filler cap hole this suggests crankcass compression due to worn rings, but as said above make sure the mixture and timing are correct before condemning the engine!

Cheers,

Steve.

[nicknicknick]

Quick update for useful information - Spark plugs 2,3,4 were very oily, but 1 was fine? Could this mean blown headgasket?

[Stevie W]

Quick update for useful information - Spark plugs 2,3,4 were very oily, but 1 was fine? Could this mean blown headgasket?

Does now sound like a worn engine if the plugs are oily but could also be head gasket problems.
A compression test would tell you if there was a problem with these cylinders.

[nicknicknick]

So is there anyway I could tell if it's a blown headgasket or a worn engine (piston rings, valve stem etc, praying its not this) ?

[bmcecosse]

Just be careful - you say 'loud bang' - it's not unknown for the fuel pump to leak petrol into the sump mixing with the oil. This would be shown as oil level RISING - has this been the case ?? If so - it's VERY dangerous - there could obviously be quite an explosion/fire - bursting the engine casing. Does the oil seem thin - does it smell strongly of petrol ??

[nicknicknick]

Just be careful - you say 'loud bang' - it's not unknown for the fuel pump to leak petrol into the sump mixing with the oil. This would be shown as oil level RISING - has this been the case ?? If so - it's VERY dangerous - there could obviously be quite an explosion/fire - bursting the engine casing. Does the oil seem thin - does it smell strongly of petrol ??

Thanks for the warning! The oil doesnt seem to be rising, so I think it's not that. Though i will be a lot more careful!
I took the spark plugs off today (after trying to start it, only ran for 5 seconds before cutting out) and smoke was coming out from 2 holes (1,3) but not the others (2,4) very confusing! I'm guessing it's just from whatever position the cylinders were left it when the engine stopped?

[Stevie W]

So is there anyway I could tell if it's a blown headgasket or a worn engine (piston rings, valve stem etc, praying its not this) ?

If you have worn rings the compression can be improved temporarily by squirting some oil down the bores. This helps to seal the worn rings against the cylinder wall, hence improving compression.

If this has no effect it usually means valves not sealing properly on their seats (more often than not the exhaust valves), or the head gasket is on it's way out. If the engine is unusable as it is whipping the head off can tell you a great deal. At least you will know what condition the bores are in, what the valves are like and whether the head gasket has failed. These usually go between cylinders 2 and 3 but can easily fail elswhere.

Steve.

[m1tch]

I used some 'piston seal' stuff you get from halfords, isn't a permanent fix, but can definatly sort the compression for a bit to check if its that or not