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MG Midget and Sprite Technical - Cutting out, missing, shurely the distributor cap?

It took me 3 hours to get the racer started today. Turned over, fuel pumping fine, fuel reaching floatbowls fine. Spark coming from all 4 plugs, checked against earth.

So eventually I just keep fiddling with it, checking everything, leads, etc. Suddenly it turns on the key (as it should!). No idea why.

Take it out for a drive, seems really good, starts mis-firing at high-load (4k revs+), but drives ok at low revs. Carry on and then someway down the A322 it loses power and essentially cuts out. I thought it was petrol and walked to get some petrol, but no, not that!.. So I had to be recovered....

I think this is absolutely standard distributor cap with a bit of play vibrating, wearing unevenly and then eventually just failing. I had very similar on my own midget last summer... I can't check it with my own Midget distributor as the Sprite has a different (Aldon) cap, so I'll order another... as well as a rotar...

The points look worn. I've tried to take a pic of the dist cap but to no success...

Am I right? :)

Rich Amos (1 Sprite 1 Midget!)

How much play in the dist. shaft....could be the bearing is worn ....it maybe time for a pretonix ign. chip and lose the points...or rebuild the dissy to use the points

Prop
Prop***The End in 2012

Well, probably!

You know how hard it is to track exactly which bit of the ignition system is failing (esp. with intermittent faults), but the last thing you thing you want is problems on the grid.

So change all of it.

AndyB
a borris

Racing is expensive!

AndyB
a borris

If it is still on points, i would recommend electronic - ignitor etc. Get a good rotor arm also - I use the minispares blue one - never had a failure now in 3 seasons. Aldon say they never have had a failure with their Bosch ones, so they should be OK as well. Don't spend a fortune on the leads btw.
John Collinson

I'm getting a new cap and rotor to start with, and going from there. If that doesn't work, new leads. Repeat and rinse!

And yes, it needs electronic ignition. But this should be enough for now, hopefully!
Rich Amos (1 Sprite 1 Midget!)

shall I say it?

no

I dont think so...

Rich get an electronic ignition system, there was one mentioned here recently at a very reasonable price

then you can ditch the condens....

Oh blimey wasnt going to mention the c....

Get a new rotor arm too! the Bosch ones will do nicely as will the blue minspares ones recommended by John

check inside the cap for feathery traces of tracking, looks like a trail of blacker soot sometimes (if you are lucky) If you find the traces you can tippex them out (yup, honestly, Tippex or Snopaque)

With a multimeter check for dwell on the points 50ºor 55º is fine and will give a better setting for ignition timing than just a feeler gauge or even checking and measuring by eye. It sounds as if your points may have closed up a tad...

Keep us posted
Bill sdgpm

Got a new cap on order as well as the recommended rotor. It already had that rotor in it interestingly enough.

The contact points inside the cap are buggered. One of them is worn more than the one on the otherside and has some plastic chipped off around it! Looks like this here cap has had a rough ride!
Rich Amos (1 Sprite 1 Midget!)

if the contactors inside the cap are buggered remember there are two ways this can happen

Spindle wear is far more common than you'd think, if you can feel any movement when you shake the spindle side to side that COULD be it , but I rather think the cap hadn't been replaced properly some time which set it offset against the rotor arm. That wears caps out like a shot...
Bill sdgpm

Spindle is fine (thankfully). I think it's cap, I'm going for cap, I've got 20 quid (cap + rotor + postage) on it, so I better be right!
Rich Amos (1 Sprite 1 Midget!)

There are also points on the market wich are bodgy when new. the make a short circuit to the pillar(?) I've had the same, put in another new set and all was fine.
Alex G Matla

Rich,

most of the common everyday auto parts stores carry both the rotor and the cap in stock, certianly save the 8 quid your spending in postage and you get the part right then,,,,least thats here in the USA

Prop
Prop***The End in 2012

I think Swiftune do a competition condensor now, but if the regs allow electronic then there is a big advantage there.
John Collinson

New cap on it's way, new rotor on it's way, and a spare points and condensor on it's way in case it's that. Cost me very little but might get the car happily running!

We'll be fitting electronic before Oulton I would think.
Rich Amos (1 Sprite 1 Midget!)

Peter Caldwell has a little fake condenser that uses conventional points as a trigger to fire a solid state switch in the "condensor". He claims that the points will last ... (well he still hasn't worn out a set). Since they are only switching low voltage and the electronics hidden in the "condenser" are switching the high voltage, there is not arcing to burn the points.
Trevor Jessie

>>> We'll be fitting electronic before Oulton I would think. <<<

Good thought - you wouldn't want all the spectators, corner marshals, etc. all shouting "Check the condenser!" That would be embarrassing.

;-)

-:G:-
Gryf Ketcherside

Just one further point to add to the above, if still using points and are after that every last bit of power;

I recently found on checking an old distributer, that the points gaps 1 to 4, differed by as much as 5 thou, i.e. one was 19 thou whilst the greatest was 24 thou.

I first I though it was my feeling gauge technique, so I put the distributer in the vice, and put a Dial Test Indicator on the back of the points and repeated the sequence. The difference persisted.

This wouldn't be the cause of your breakdown, but thought to mention if you're in the optimising mode.

Also on the subject of optimsied spark-advance/CR/power, I read a mid 90's Vizard article that said he sets the no.s 1,2 and 4 cylinder conbustion chambers a litttle higher than the no. 3 as the no. 3 runs hottest and detonates first. Would be interested if other contributers have done this, and by how much. This assumes that there is a coolant take-off, at the heater outlet at the rear of the head.

James
J E G Eastwood 1

Interesting, thanks!

I think my restriction on Saturday will be actually staying on the track. The timing will likely be the least of my worries!

Saying all that, being a whipper snapper, I've never had a Spridget with points and I don't intend to keep them on this one for long either!

Igniter is clearly getting fitted after Donington.
Rich Amos (1 Sprite 1 Midget!)

I carry a spare Rich so you can borrow it at Donington if there is still a problem.
John Collinson

Trevor,
I think you will find that Peter's gadget is still switching the same ~10VDC as the points would be. The difference is in the amperage. It switches much less current than the points do.
David "easy as 'PIE'" Lieb
David Lieb

Ahh yes thanks David. Don't know where my head was on that one.
Trevor Jessie

anyone got a link to this peter cardwell condensor device, 1st I have heard of it.

Prop
Prop***The End in 2012

Call or email Peter Caldwell (no R)

http://www.nosimport.com/
Trevor Jessie

It's working! Replaced rotor and distributor cap because I couldn't seem to fire it with just a new cap, but that may have been more to do with me not using the choke enough!

It's running, it's not missing, it's running beautifully. I've got a spare rotor, and a spare set of points & condenser now. Sorted!
Rich Amos (1 Sprite 1 Midget!)

'Standard' rotor arms made today are made of a mix that, apparantly, is more conductive than of old. That combined with a longer rivet causes a short between the end of the rivet and the dizzy spindle.
Aldon Automotive or Distributor Doctor sell rotors that are supposed to eliminate the problem. depending upon what type of electronic ignition you fit then a rotor arm will still be required unless going to mega jolt or similar.
Swiftune do a competition condensor ar about £25.
Alan Anstead

This thread was discussed between 29/03/2009 and 01/04/2009

MG Midget and Sprite Technical index

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