3 cylinder Morris?

[redduster]

Started our Moggy on Saunday and engine was lumpy which is due to no 4 cylinder not wishing to play with the others.
Had been fine until then.
Checked by removing plug lead, removed plug, which was very black, swapped with plug from no 1 and same problem with no4?
Checked mixture, lifted jet, slight engine speed increase which the book says is OK.
Only thing I changed was I replaced thee old, perished rubber connector from carb to advance/retard pipe with new and wondered if this could have any affect on running, but only affects cylinder 4?
I did swap the pipe for the old one but misfire still there.
Any ideas?
Cheers

[MarkyB]

Check the compression and the tappets.
Sounds like a valve or head gasket problem.

[bmcecosse]

Indeed - valve gaps would be my first check - then compression... That's if you are sure the HT is appearing at the plug??

[mogbob]

As Roy says..eliminate the No 4 plug lead first.Remove spark plug and reconnect HT lead to it.Lay it on the block/ good metal earth and hit the solenoid button with the ignition on.. and observe the spark ( ? ..fingers crossed ).Don't touch the spark plug with bare hands, use well insulated pliers, if you must to hold against the block.If no spark,examine the distributor cap generally and the internal terminal for cracks/dirt corrosion, etc.Is the lead firmly attached both ends ?
Replace lead ( you may want to replace all of them, if they are all of the same vintage ) and /or distributor cap, depending on what you find.
If you get a decent spark then move onto the other suggestions.
Bob

[redduster]

Well armed with a new rocker gasket, feeler gauges etc I began the check over.
I thought Iwould attempt a start and it did run on 4 cyliners for 5 secs, tried again went down to 3 then nothing.
No
solenoid button, presume replaced with a unit without one, so havinglong arms just managed to turn key with no 4 plugagainst block no spark, and then no 1 plig no spark either.
Closed bonnet and resorted to this for advice.
Neither fuses blown.
HT leads appear new, Bosch silicone.
Engine turns over fine so stumped.
Is it delving into distributor?

[MarkyB]

Examine the inside of the distributor cap for any signs of tracking ie sparks going astray.
It needs to nice and clean inside too.
If you have a spare try it.

Not a great fan of carbon leads, replace with copper ones!

[redduster]

Thanks for all the suggestions and apologies for not replying sooner but circumstances have restricted my movements. Fault eventually found, eventually, with break in external wire on distributor causing the intermittent fault.

[bmcecosse]

Thanks for coming back - doesn't really explain why only #4 affected - or do you mean a break in the HT lead to #4 was the problem??