What have I done? MGB problem
Turbo Mini Forums

I have an MGB GT which is my daily driver, it has had an occasional misfire which would come and go at random so I decided to take a look at the dizzy. I found the cap in a poor state and the wire from the coil to the condenser was just pushed in and making a poor contact. I replaced the cap, rotor and condenser on my 998 Mini years ago but only ran it for a couple of hundred miles before changing to electronic. As they are both 45D4s I decided to change over the cap, rotor and condenser as the part numbers were all the same, I also cleaned everything up and oiled all the relevant bits.

When I refitted it and started it up it sounded a bit rough but I set the timing and let it warm up and it sounded good, I took it out for a test drive and it drove really well for about 50 yards before it started to misfire, a larger throttle opening made it much worse and it soon cut out completely. I had to leave it for 5 minutes before it would restart, when it did it ran ok at idle after a few seconds. Under load the same happened again and it soon cut out. Now it is really difficult to start at all and very difficult to keep running when it does, I can smell there is a lot of unburnt fuel in the exhaust so it is clearly not burning it all even though the same choke position would have had it running perfectly before. What I can't understand is that all the parts I have changed were fine when on my Mini, I can't change back any of them as all the parts I removed pretty much fell apart. Before I buy new everything until I eliminate the problem can anyone suggest anything? I can't understand what I could have done to make it run this badly.

(I hope this post is ok here, I don't know of a UK based MGB forum and I trust the knowledge of people on here. If it should be in a different section please move it.)

back to basics - did you tighten the dizzy up after setting the timing?

Condenser, even if is newish:

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=337996

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Yes, I tightened it up initially, I have now slackened it off but no amount of moving it around will make it run anywhere near ok. It is so bad that having the timing massively retarded makes almost no difference. I have checked all the obvious things I can think of such as firing order and connections.

Could a bad condenser cause a car to barely run at all, I thought they just smoothed out the spark? The thought had crossed my mind but it would seem strange that 6 years of sitting in my garage would cause it to fail.

The symptoms sound like condenser failure. 6 years sitting in a garage is probably worse than beng in use. Is the garage damp?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I have repaired the wire on the condenser I removed so as soon as it stops raining I will go and test it out, I hope it is that as it will be a simple fix.

It is very slightly damp in the garage, but the condenser has been fitted inside a dizzy with the cap on which has been in a box, in a crate. I will let you know the outcome as soon as I can test it.

another vote for condensor here... they really are temramental little C**T's

As above, points and condenser really are pretty duff, if it's your daily driver then I'd definitely lay out on an electronic ign kit.

We've fitted electronic ignition to ours. Best £30 spent on it.

In the 13's at last!.. Just

It's been my plan to switch to electronic ignition, I just haven't decided which one to go for yet. There seems to be a lot of debate over which is best, which are terrible etc. I've got other cars I can use so it's not a massive problem other than the MG blocking most the cars on the drive! I only use the MG as it is the most fuel efficient and it has an 8-Track :) Thanks for the help so far.

I've just swapped the condenser back to the old one and it runs beautifully again. I never knew a bad condenser could cause such severe problems or have such a short life, it would have saved me a lot of time yesterday to know that as I was sure it was something I had done. Thanks for help everyone, it is very much appreciated. Time to buy electronic ignition I think.

No.1 B series resource now as well