2 replies to this topic

[Walkers1985]

Hi,
Im running a standard 998cc 71 clubman and i'm suffering from a bit of misfire atm under acceleration and only after a longish run.
The only thing I can think of that can have caused this is my local garage ran out of petrol in it while taking it for an mot so I'm assuming the carb is clogged up will it be enough to just clean out the float chamber or am I gonna need to do the needle and jet as well?
I was thinking of using some compressed air and a cloth?
Initially I thought it was a fuel/air ratio issue so tried adjusting the mixture but this seems to make no difference to the running and when I push in the piston lifting pin it cuts out immediately regardless of mixture strength?
I tried looking for some clues in the forums but nothing seems to exactly match this problem.
Cheers

[tiger99]

You should strip and clean the carburettor if you suspect it. But it is not a good idea to use compressed air near fuel, and what problem would it solve anyway? But check that the piston falls freely. Clean piston and dashpot. Refill with proper SU oil or 3 in 1, not engine oil. All of this is worth doing every year or thereabouts.

But be aware that this may also be an ignition problem. Check spark plugs and their colour, leads, rotor arm and cap. Replace the points and condenser. Get proper new parts from Distributor Doctor, not a Mini specialist. Check coil by substituting a known good one.

[carbon]

+1 for Tiger's suggestion about checking ignition, the misfiring under load can be due to weak spark.

 

As the problem is noticeable after a long run, the next time this happens I would check the temperature of the ignition coil. Put you hand on the coil, if it's too hot to keep you hand on it comfortably then this may be the cause.

 

Are you still running the original distributor? And what make/type of coil do you have fitted?

Edited by carbon, 21 August 2016 - 06:01 PM.