Misfiring engine

[pingis]

Last autumn the Moggy was working fine when I parked it in our garage for its winter rest. Last weekend I thought it was time to charge the battery and take it for a ride. I was so surprised when I tried starting it after the harsh Swedish winter and it started directly without any additional charging of the battery. This after a winter in a garage with temperatures between -20 and -30C for months. I topped up all fluids and off we went. After half an hour or so the 948cc started misfiring at high(ish) rpm's. We made it back home but the motor fired on three, sometimes two cylinders. I had a look under the dizzy cap and found a lead (the one that connects the breaker points with the outside) that looked a bit sad. I replaced it and went for another ride. The same thing happened after half an hour. Today I cleaned the fuel filters in both the carb (looked nice) and the fuel pump (had some rust fragments in it) and went for a ride again and... 30 minutes later the Moggy started misfiring again. The spark plugs are in good condition, the breaker points, condenser, rotor arm, distributor cap are all almost new. The carbureter was rebuilt by a specialist company about two years ago. Is there anyone here who has experienced the same type of problems and would like to share some knowledge? Any ideas would be highly appreciated.

[Neil MG]

Condenser!

[bmcecosse]

Or vacuum forming in the fuel tank - but condenser is MUCH more likely.

[pingis]

Thank you for helping. I thoght I wouldn't have to replace the condenser for a couple of years since the one we are using has only been used for about 50 hours . We are expecting heavy rain so I have put the Moggy in the garage. I'll take it out again some time next week and try with a known working second hand condenser. I don't think there could be vacuum in the tank since the rubber bracket on the fuel cap is quite dry. I'll let you know if this was a "condenser-problem" as soon as I know. Have a great weekend all.

[chrisryder]

to rule out a vacuum in the tank, if you're driving and it happens again, first thing to do is go and take the fuel cap off. if you hear a hissing/sucking noise, that's your problem!

condenser is also quite likely, especially if it's new. on our Minors On Tour trip last week, over 100 minors went, and half a dozen needed condensers replacing, a lot of them had recently had new ones!

[bmcecosse]

Hopefully none of them needed the coil changing.....