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MG MGA - Strugling with the motor

Hi,

For sometime now I have problems with my MGA MKII of 62. In the past, when I was driving about 20 miles, the motor started to turn irregular and finally stopped turning. After some time waiting, I could start it again. I checked the ignition system and even changed the ignition coil. I seemed that the problem was solved. Could drive several trips for more then 30 miles with any problems.

Last week, the symphtons arrived more or less again. I drove for about 30 miles. Car was running very smoothly and nicely, so no problem. I stopped the car and switched off the engine for about 10 minutes. When I started the car again, I felt immediatly something was wrong again. The motors seems to turn nicely in idle speed (about 900 rpm). But when I want to speed up, the car starts to shake. It is like there is not enough power enough. The same thing I see in the 2nd or 3rd gear. As long I stay steady with the speed, it seems ok. When I want to speed up the car, the problems comes. I hear at the exhaust small bangs, like it is missing firing of the spark plugs.

Anyone ideas what it can be ans what to do? How to check things?

Thanks

Marc
Marc Vernackt

Marc, have you tried changing the rotor arm ? I have heard from several sources that they can cause exactly the sort of intermittent fault you describe and I know personally of someone driven to distraction until he found the cause. Also might need a new distributor cap.
David
D C GRAHAME

Marc,

Are the small bangs coming from the exhaust pipe or the carburators?

If it is the carburators check 1)the timing and 2) the fuel mixture.

I had similar problems and discovered I was driving with a very, very rich mixture.
T McCarthy

Marc Another thought- try putting your hand on the coil. If it is getting very hot that also might be the cause.
David
D C GRAHAME

Hi all,

Thank for the info.

D C GRAHAME, South Yorkshire, United Kingdom => changed already the distributor cap and rotor

T McCarthy, Michigan, USA => I hear the small bangs coming out of the exhaust, at the time I want to speedup the car

D C GRAHAME, South Yorkshire, United Kingdom => Yes the coil becomes hot (I assume this is still OK). Changed the coil also and measured even the resistance of the coil and should be in spec.


I'm almost sure the cause lies somewhere in the ignition system and not in the fuel supply (since I was able to drive further). Could it be that my vacuum tube and therefore my advanced timing is not working fine? A lead to the spark is broken when getting hot? (although I was pulling off one cable at the time for the spark when motor was running and heared the spark noise when putting the cable back on the spark. Also the motor was not running as nice at idle speed when one sparkcable was disconnected)

Any further ideas are welcome

Regards

Marc
Marc Vernackt

Marc
Where are you in Belgium? I have a strobe light and can lend you a hand to fix the problem if you like. I am just on the edge of Brussels.

I would also check the engine earthing strap as this can give intermittant current if not correctly connected. It would however normally show itself when trying to start the car as this draws most current.

It is also possible that the distributor centrifugal advance is also in need of some lubrication. If the weights stick then things will go a bit lumpy.

Best regards
Neil
Neil Purves

Broken flex wire inside the distributor causing intermittent contact when vacuum advance mechanism moves. There are two flex wires. Photo here: http://mgaguru.com/mgtech/ignition/ig106.htm
Barney Gaylord

Marc - Barney could be right and also check the isolator on the live pole that it is not worn, incorrectly assembled or damaged or if any wire is worn through to the core. Also if the wire is cracked there can be arcing to ground when the humidity/temp goes up.

Neil

Neil Purves

Don't know if you replaced it yet but a bad condensor can cause poor running above idle (sometimes new ones are bad). A few years back our A" would be running down the road fine at speed and with no warning would cut out and come right back in a second, pulled my hair out for a while before finding the condensor was intermittant.
J Heisenfeldt

Hi all,

Thanks again for the feedback.

I will check this weekend once more the distributor and the flex wires. I'm considering to install an electronic ignition system, but want first to be sure the current system works fine and cause of my problems lies indeed in the ignition system.

Of course I will keep you all informed.

Neil,

I live in Overmere (between Gent and Dendermonde). Maybe indeed a good idea to check once the time with the Stroboscope. Maybe we can get in contact. Currently having this week a night shift. My email is mvernackt@skynet.be - 0473/770061

Thanks

Marc
Marc Vernackt

Marc,
Het is inderdaad mogelijk dat het de condensator is. Deze kan na verloop van tijd stuk gaan met alle symptomen zoals u die beschrijft. Het is mogelijk dat de bobine verkeerd aangesloten is waardoor eveneens de condensator de geest geeft (de PLUS van de bobine moet bij de MGA aan de contactpunten liggen).
Jaren geleden had ik dezelfde problemen met mijn MGA: een doorgebrande condensator als gevolg van een verkeerd aangesloten bobine.
Denkelijk is dit toch een ontstekingsprobleem.
Succes !

Niek,

PS: Sorry folks, but I could explain this technical story better in Dutch (Flemish) than in English.
D.G.J. Herwegh

This thread was discussed between 08/10/2007 and 10/10/2007

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