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MG Midget and Sprite Technical - Starting issues

Hi, I started the day checking the advance and although I can make the distributor move by sucking when I hold the pressure it turns back so I think I may have a damaged diaphragm. Thought I'd check the points next, took them off to clean them but upon re assembly the engine spins but won't spark! I checked opening points and checking a light on the base plate but nothing... Checked earth to switch side of coil and got a light. So I changed the points for a new set, nothing changed, changed coil again no change, changed condenser and still nothing....... So it started and ran before I started checking albeit wouldn't pick up which is why I started at the vacuum advance. I used a syringe to 'suck' the vacuum pipe and did depress the syringe back into the pipe, would that have done something or is it when I removed the points? It's as if I've knocked a wire off somewhere. As you can appreciate most confusing and frustrating, can anyone help, please. Thanks Tim
Tim Pollock-Gore

Guessing a bit here, as I don't know which model your car is and whether you have a 23, 25 or 45D distributor.

When you replaced the points, did you refit the low tension lead on top of, or underneath the insulator?

Is the coil getting very hot?
Dave O'Neill 2

Im with dave... how that spring and nylon bushing fit to avoid metal contact with the dissy is confussing the 1st time out

Can you take a few good photos of inside the dissy of all the parts so we can have a gander

Did the vacume advance move the ignition plate back and forth when appling suction (vacume) to it... if there was movment then it was fine

Did you gap the points on the dissy shaft lobe or on the flat spot of the dissy shaft....and you did use a feeler gauge

Prop
Prop and the Blackhole Midget

Hi, sorry I forgot some basics! It's a 62 mk1 midget with a 25 distributor. I put the LT lead on top of the insulator with condenser wire a washer and small fiddly nut. I gapped the points on the lobe with feeler gauges, moved the shaft a few times by moving the car by hand whilst in gear, then checked again and checked all 4 lobes to ensure the gap was the same. I'm not sure about the coil getting hot, although I think it did at one point but I was working outside in the sun ( what a pleasure) .
As regards the vacuum when I sucked with the syringe it moved the base plate clockwise but then it slowly returned to its original position without me releasing the air. I did this a few times and pressed the syringe thereby pushing air back through the pipe, not sure if this can damage anything?
I hope the picture helps, it only seems to allow one .
Thanks for your help and comments
Tim


Tim Pollock-Gore

Another photo


Tim Pollock-Gore

I hope these help?
Thanks
Tim


Tim Pollock-Gore

Bingo!

The LT wire and condenser wire should be underneath the insulator, in contact with the spring.

If they are on top of the insulator, they will be permanently grounded and your coil will get hot, as it is permanently on with the ignition.
Dave O'Neill 2

What Dave said.

The top hat shaped insulator should fit on the top of the spring with the points and condensor eye terminals underneath so the LT lead can go the earth via the spring and the points.


We've all done it, but usually only the once!


SR Smith 1

We have all done it usually ((""ONLY once"")) ???

Uummm okay, yeah sure, ive only done this ONCE myself also, hmmmm...

Can someone define the word "usually" please

Hahaha

Prop
Prop and the Blackhole Midget

Oh my word what a goof, I shall be on the job tomorrow and switch them round. I even remember thinking have I got these in the correct position. Thank you very much, I will of course report on the outcome. Thanks. Tim
Tim Pollock-Gore

If the vacume advance is moving, with vacume applied then its good, we rarely ever hear of the vac advance going bad...its when they dont move you get problems

If anything id look at the dog legs and springs inside the dissy for wear, corrosion, and dirt build up.

Weak springs will allow the dissy to advance alot faster. Making the spark plug fire much more faster/premature before the fuel charge is ready to be exploded and not giving full force to shove the piston back down the cly

frozen, stiff or rusted dogs legs will not fly apart with centrifugal force thus not allowing the dissy to advance when it should. Retarding the time of explosion...making the explosion to late AFTER the piston has already started down the cly

Prop
Prop and the Blackhole Midget

Hi, I've done as suggested but still nothing.. I ran a test light from earth to the spring and no light! Then earth to switch side of coil and got a light. I wonder what I've done now? Sorry to be a pain. Thanks Tim
Tim Pollock-Gore

Hi Tim,

I had similar when I started fixing my Midge and could not find the problem. Everyone on here was really helpful however what sorted it for me was pictures of the distributer and associated parts and the good pics were in the handbook. You do of course need the right handbook for the model but I can vouch for the pics being spot on.

I put my LT lead on the correct position but the 'wrong' way up. Just caught the side of the dizzy enough to short. Clear as day pic in the handbook.

Hope this helps.

Dave
Dave Squire

Whem you connected your test light to the spring, were the points open or closed?

If closed, your test lamp won't light, as the points are earthed when closed.
Dave O'Neill 2

Hi Dave, no points were open.
Tim Pollock-Gore

Is the condensor new or untested?

If it is then Try the old one ... being that we know its good

Prop
Prop and the Blackhole Midget

Thanks all round, it seems everyone contributed to resolving the problem. When I changed the condenser back to the old one I realised the wire is soldered/ fastened to one side of the eye connector and if put on wrong way when I tightened the nut it shorted to the post/ backplate. So turned it the other way up and as Dave 2 said " bingo" . Clearly my own fault for not being careful when I took it apart! Hopefully now a lesson learnt. Many thanks. I can now move onto the vacuum if indeed that is a problem or get inside the distributor and clean it up. Then sort the rich running and who knows I may be able to unleash more of the 40 horses it started life with..... Thanks again.
Tim Pollock-Gore

there are John Twist vids on dissys - http://www.youtube.com/user/Universitymotorsltd#g/u

parts/rebuilds from Distributor Doctor - http://www.distributordoctor.com/

I've read that dissys were out of tune within a few years of the car leaving the factory so after decades of use you can imagine they've got worse

good luck

if you could find an original Driver's Handbook relevant to your model year you find much of the information you needed here and for future servicing and maintenance, it's the one Dave mentioned
Nigel Atkins

""Thanks all round, it seems everyone contributed to resolving the problem. ""

Come on guys, really !!! Im very disappointed in you all, and esp myself

NO THREAD DRIFT !!! None whats so ever? well I hope your all proud of yourselfs



Prop
Prop and the Blackhole Midget

I have more of a problem stopping. Drinking that is. Drift enough Prop? ;)
Lawrence Slater

This thread was discussed between 21/06/2014 and 23/06/2014

MG Midget and Sprite Technical index

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