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MG MGA - Engine wont run

After years of faultless running my engine started to miss over a period of a few weeks and finally failed to start the other day fortunately in the garage. I've checked that there's fuel in the float chambers, points adjusted and the plugs spark at turn over. Every thing seems OK but before I start pulling things apart is there any other rudimentary checks I could do to locate the problem? If the plugs spark does this give a clean bill of health to the coil, condenser and distributor cap?
J H Cole


Does it only fail to start? Once running everthing is ok ?
When there is fuel, and there is a spark, the engine should start.
How long is it ago that you changed the spark plugs ?It is possible that you have a spark outside of the car but that they fail when installed.
Do you have a spark on all 4 plugs?
Or maybe the choke doesn't come out , or not far enough.


have a look here ,


Top of my list for things to check would be the timing....................Mike
m.j. moore

What is the condition of the battery and terminals? I have found in the past that a failing battery has nearly all its power absorbed by the starter and not enough left to provide that vital spark UNDER compression. On numerous occasions I found that the engine just 'caught' as I released the starter pull.

Steve Gyles

serge:it fails to start, fires and coughs a little but
wont run properly - no back firing in exhaust.
Plugs are good but I will have to check spark on all plugs. Choke works.

mj: cant see how the timing has changed but I guess I'll have to check it again.
steve: battery good engine turns over well.

Did a compression test and all cylinders OK at around 150 psi
J H Cole

Classic signs of a duff condenser
dominic clancy

Is the spark deep blue in colour or yellowish? if its on the yellow side then as DC suggests possibly the condenser.
John Bray

Be sure to get the "good" condenser from Moss ...There are apparently two grades, and one of them does not work.
E B Wesson

Thanks everyone for suggestions but three pineapples
to Dominic who got it right and saved me a lot of unnecessary testing. I dug up an old condenser and swapped it over and now the engine runs. Not sure I understand why the plugs sparked with a duff condenser but might it be intermittent failure under pressure?
Now to order from Moss, seems strange that I have to specify that I want a decent one!
J H Cole

You could always go electronic. Points and condensers become a thing of the past. Never had to worry about much inside that cap in the last 10 years other than one duff rotor arm, since replaced with a Distributor Doctor Red version.

Steve Gyles

Am I right in thinking the pertronix? + earth is about the best?
J H Cole

You could just leave the current one in, it probably won't fail anyway as it's only the repro ones that are cr@p.

But I too fitted the Pertronix years ago, switching to -ve earth at the same time.
dominic clancy

Before buying a condenser read my thread from a couple of weeks ago titles 'Condenser Failure/Good Trip' particularly my last comments on Moss condensers.

Paul Dean

I used the Aldon Flamethrower which I think is a Pertronix in disguise. It's been a faithful servant. Mine is negative earth.

Steve Gyles

I will probably buy one as a spare but are there any reliable suppliers in the UK?
Paul I did a search and your thread did not come up using the title you gave???
J H Cole

I am with Dominic - if the old capacitor (condenser) works, don't change it when the points are renewed. Capacitors don't wear out, but new ones are very apt to fail right out of the box. Cheers - Dave
D W DuBois

My thread is only 19 items from the top of the list with date as 22 May. By the way I do agree with Dominic and I have gone back to one I probably installed in 1970s.

Paul Dean

Got thanks Paul I was looking in archive before.
J H Cole

I have fitted a complete Pertronix Distributor to the 1900 engine in my MGA.
The car definitely runs great with it but if you have fitted an alternator like me, just double check the output voltage of the alternator throughout the rev range before you fit the electronic distributor.

The wiring on my alternator wiring-loom had developed a poor connection because of a dry joint.
(I had used the original voltage regulator as a connector block for the new alternator wiring and one of the screw connectors was a poor fit.

The alternators output voltage measured 14.1v at 1000rpm but went up to over 17v at 3500 rpm!
I had assumed that the alternator would produce a constant voltage.

This burnt out two Pertronix distributors in a few weeks!

Once I realised the problem was due to my cars wiring rather than anything to do with Pertronix I rewired the connection separate to the old regulator box and this has fixed the over voltage issue. I now get the correct 14.1v max at all rev bands.

So the Pertronix unit will go back on the engine once it is fixed.

I hope this may save someone else from making the same expensive mistake.


Glad you have fixed it JH
c firth

You can get a complete new electronic distributor for not much more than the price of the unit. That way you also know the vacuum advance and mechanical advance are working correctly. I fitted one and the car runs fantastic!

This thread was discussed between 01/06/2014 and 03/06/2014

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