Running on 3 cylinders only. Problem

[pippinpickup]

Hello MM people,

Just joined the forum.

I have a 1098 engine in my Morris pick-up, and it's only running on 3 cylinders now.
Last night driving home from work there was a bit of a pop 'n' bang noise and the car lost a bit of power. I got home okay and this morning I have had a look under the bonnet (the engine is still there !).

I've done some checks and tests, and have come to the conclusion that one of the cylinders isn't working correctly. The spark plug that was in there was a moist shiny black (the other 3 plugs were fine), I replaced the plug but to no avail. I then did a spark plug test, running the engine and checking to see if the plug (tried two different plugs) was sparking against the block. That was fine and healthy.
I took the rocker cover off, everything moving up and down and seemed to be in order.

So, the cylinder is getting the spark, fuel is going in (I think, by the black deposit on the spark plug I mentioned). Would it be some sort of compression issue/valve thing ?? ....... Here my mechanical knowledge ends !

Has anybody got any ideas please ?
I'm working down near Charles Ware next week so may have to take it there for repairs if it isn't straight forward

all the best,
Phil

[lambrettalad]

Sounds very like head gasket,which cylinder is misfiring?

[simmitc]

Check the compression. Could be a head gasket or a valve.

[bmcecosse]

As above - gasket or valve. Possible hole in piston - but there would be a LOT of smoke... My advice - DO NOT run the engine again until you get it fixed. Compression test required urgently. It 'could' I suppose be simply a faulty HT lead......so you could try another, but I rather doubt it. I know where I would NOT take it for repairs.......

[pippinpickup]

Thanks for the replies.

I took the head off and saw what the problem was, a hole in a valve.

Managed to get 7 new valves Saturday morning so ground down the valve seats, replace 7 of the 8 valves, and now the car goes super.

Now to fix the horn, some days it works, other days it doesn't !

[David53]

Good result but why replace only 7 valves? Why not do the lot while you're at it?

[lambrettalad]

He/she could only get 7

[MarkyB]

As long as the missing one is an inlet, shouldn't be an issue.

[bmcecosse]

Well done - now remember to retorque the head (44 ft lbf) - and then reset the valve gaps... 15 thou exhausts and 12 thou inlets.

[pippinpickup]

Head is torqued up and valve gaps reset.

The Moggy centre in Bristol only had 7 valves in stock, so bought those and so left one of the old valves in. My pick-up is my only vehicle, so had to get it back on the road asp.

By the way, when putting the valve pushrods back in, I couldn't get them in all the way down properly and didn't know what the problem was. Luckily my handy brother was at hand, and he took off the side plates to reveal that the sleeves had come up with the suction and misaligned when pulling out the rods. Remember that for next time !

[bmcecosse]

Yes! You need to 'wiggle' the push rods as you pull them up. A spare head is a good investment - search ebay for a 'good buy' (or ask on here of course) - and then if/when it goes wrong - an easy swap over.