misfire

[mick sharpe]

can anyone help i have a rebuilt 1098 in my minor van which will only run properly when you ease number 2 plug cap away from the plug,i have tryed another cap,rotor arm,leads,and plugs,could it be the dizzy? i have never come across this before,any help is much appreciated thanks mick

[Alec]

Hello Mick,
my first thought is a bad plug, that trick was one that was used to clear fouled plugs. I know you have changed them, but what does it look like when you remove it? What rating of plug are you using?

Alec

[mick sharpe]

Thanks alec for your reply,ive changed the plugs from 3and 4 but still misfires on number 2 cylinder.the plug out of number 2 is perfect in the other cylinders. it is black when i removed it but only just built engine and trying to set it up mixture etc but when its not running on all i cant get it set up.thanks again mick

[Alec]

Hello Mick,

if you are not already aware, set the mixture 12 flats down from the jet flush with the bridge, that should be very close. I'm assuming the choke is returning fully also.
If only the number two cylinder is showing rich then that is very odd. My other though is an excessive amount of oil in that cylinder. It would be benefial, if you haven't already, to get the engine really warm by driving it and see if you can then put the cap back on the plug. If so it would indicate that the plug is fouling, is the engine at all smoky?

Alec

[Willie]

In the old days! on engines which persisted in oiling up their plugs
it was beneficial to obtain a small shirt button made of BONE and
wire it so that it was between the plug top and the plug lead. This
gave a bettter spark because the voltage had to leap across the
small gap between the wires on the button! Don't laugh, it worked
on my Austin sevens. The fact that yours seems to improve if you
loosen the no.2 plug top suggests a similar condition. I must say
that it sound as though the problem is inside the no.2 cylinder.
I assume that the modern plastic buttons will perform just as well.

[bmcecosse]

Sounds like you have very poor compression on #2. What was the extent of the 'rebuild' ? Check simple things like valve clearances - and have you got the plug leads in the right order ? But really - you need an urgent compression test to find out what's going on.

[mick sharpe]

thanks for all your help. the rebuild was a total rebuld, i have done a cylinder leakage test, all cylinders were perfect.so i still have the problem ill have another mess tomorrow,i dont know what yet.the plug on 2 is still black when i got it out to do the leakage test.ive never heard of the button thing,but i would rather cure the problem as the rest of the van has been totally rebuilt over 3 years its just theses last few bits before i can take it for mot.
thanks mick

[rayofleamington]

the rebuild was a total rebuld, i have done a cylinder leakage test, all cylinders were perfect.

Was it a 'proffesional' rebuild or a home rebuild? It certainly seems like your getting oil into #2 so that's not good. If it was a proffesional rebuild then you should be careful to check with them before doing any dissassembly as they could refuse any interweest in it.

Has the head been reworked also? If not, then was the engine fine using the same head before rebuild? (that would rule out problems with the head).
Personally from my limited experience I would doubt that the head would cause enough oil leakage to make a missfire, so you have to worry about the bores and rings

If there isn't much smoke, then you should be able to pass the MOT anyway. I doubt the problem will go away with some driving but at least you get a chance to see how it behaves under normal driving.

[bmcecosse]

Maybe it's just a dodgey dizzy cap and/or spark plug lead ? Forlorn hope really, but worthwhile trying another one just in case !

[mick sharpe]

at last just got my van running put a new dizzy in set timing rough it started first time run on all 4 cylinders,thanks to everyone who tryed to help mick

[bmcecosse]

Well done !