4 replies to this topic

[disco5619]

Just brought car back from mot with a pass but they were surprised that the car passed on 3 cylinders. When driving to the garage the car went fine but when at lights was only firing on 3 cylinders.
Before the mot i tried to set up the running using a gunson and was unable to set the mixture up and the flame stayed yellow whatever position i set the carb at.
Do i have a faulty carb or is it a bit more problematic i.e. a top end fault with a sticking valve?


Guidance would be helpful

Cheers
Disco

[jetblack81]

Hi disco. I am asuming you mean a gunson colourtune for spark plugs when you talk about a yellow flame?? You haven't said whether its single or twin carb and if the ignition parts are well serviced? If its running on 3 cylinders im guessing you have checked back through the leads to the dizzy and rotor arm to see if there is nothing obvious that looks out of place or worn. Try another set of plugs maybe to start with, sometimes these things are trial and error.

[freshairmini]

If you are only firing on 3 cylinders then you need to check the spark plug and ht lead to see if its broken. Try swapping round one of the other HT leads or spark plugs to see if its a problem with them. you will soon enough find out as the non firing cylinder should move with swapping the lead or spark plug if they are at fault.

Also if you had a sticking valve it would run like crap.

[JonnyBMX]

if your ignition system all seems to be working corrctly you could check the valve clearances

[bmcecosse]

Just fit a new plug in place of the one not firing - is it ok now?