Morris Minor Owners Club

Went out in my morris last night and the engine started making a strange noise. it sounds like a loud pinking noise when even gently accelerating. one of the cylinders seems to be running on reduced power when the plug lead is removed from 3 the isn't much difference to the engine speed and the engine seems to be missing a bit on this cylinder anyone got any idea what has happened. have checked timing and it's fine. it's 1098 engine.

Pop the plug out and see the condition of it.

should have stated that I've looked at all plugs and they all look normal with a brown tinge.

if the plugs all look ok and all produce a good spark, then next step could be a compression test.

Yes as Ray says, compression test, although blown head gasket tends to reduce compression on adjacent cylinders, so you get two down on power. Might be a leaking valve on #3. Pinking sounds suggests pre ignition, and if only on one cylinder, might be a hot spot due to carbon build up on #3, caused by leaky valve stem oil seal, or worn valve guide. Don't rule out, weak or broken valve spring either.

That said, start with easy things. Stick new plugs in it, plugs can look OK and be knackered.

Sounds like burned out valve or blown head gasket. Any bubbbles in the water ? Are the valve gaps all correct - or has one of them closed up ?

Have checked valve gaps all ok if I remove leads from both 3 or 4 does not have as much difference as removing the lead on 1 or 2 so does this mean the head gasket has probably blown between 3 & 4.will try and get hold of a compression tester tomorrow. to see if compressions are reduced on 3 & 4. no bubbles when looking at the cooling water with the engine running but I suppose it wouldn't show if just blown between 3 & 4.

Yes - the normal 'blow' is 3 to 4 or 1 to 2. Get a spare gasket ready! Note - no ned to buy a head set at great cost - just get a 998 Mini gasket from your local Autoparts place. Should only be about £5 - ask for discount!