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MG MGA - Points / Breakers,...HELP!!!

I need some hlep!!!

I was performong a minor tune up on my 1500 MGA, when I dropeed trhe small screw that holds the condensor in. Now I can't find it. Does a new screw come with a new condensor? If not, what should I do? Where can I find the screw that I need?

Also, I couldn't get the new points / breakers to fire. I may have the washers on incorrectly. I have the nylon washer on the bottom, then the spring arm, then the ignition low feed wire, and the condensor wire, then the top nylon washer, then the metal washer and nut.

Is this correct?

The low feed wire has fire when you arc it out, but then when it is connectred, it doesn't have fire.

Any ideas?

DT
Danny T

Danny. I believe the screw is a 2BA which interchanges with a stardard 10-32 machine screw. The differences are very minor and each will fit into a hole designed for the other. Any good hardware store should have 10-32 screws in stock, but, you may have to cut them to get the proper length.

Yes, you have assembled the points correctly. However, if the condensor is not grounded, the system may not work. Cannot say for sure as I have never performed this experiment. Try grounding the condensor and see what happens. You should be able, if you can recruit an assistant, to hold the condensor in place with a screwdriver (rotor and dizzy cap off) and check for spark on the coil lead.

Les
Les Bengtson

Danny - Are you shure that the screw didn't drop into the distributor? If you aren't sure, you would be well advised to take the mounting plate off and check in the bottom of the distributor. If the screw is in the bottom of the distributor, it will cause problems later on. Good luck - Dave
David DuBois

I always remove the dizzy to install new points etc. It's much easier to do this on a bench in a vice than in the engine compartment. Mark the position of the dizzy with a small dab of paint or correction fluid so that you get the position absolutely the same when putting it back.

You need to take it out and give it a good shake to make sure the screw is not in there.

Make sure that the nylon washers are correctly positioned - the two wires must make contact with the spring, but not the post.

The Condensor must be grounded. You do not get a screw with a new one. It would be the first item I would suspect in this scenario, and as it is a cheap component, just replace it. Make sure also that you have the points set correctly.

dominic clancy

Thanks Guys!!!

The "A" is up and running again. I did pull the entire distributor, installed a new condensor, cleaned and set the points, and she started up on first turn.

The screw was a smaller size than the 10-32, (10-32 is the size of screw for the points, the condensor was one size smaller).

Thanks for the help,
DT
Danny T

Always easier to pull the unit, than to try and grapple with the points in that uncomfortable position. At a glance it looks quite easy and accesssible, but once you put two hands down there and then expect to see what you're doing....need I say more. I've been pulling mine since I first owned one, back in the sixties.
R. L Carleen

The ignition will work with the condenser (capacitor, actually) ungrounded or even MISSING, BUT POINTS LIFE WOULD BE VERY SHORT! The function of the condenser is to "balance the ignition system's inductive reactances with an equal opposite capacitive reactance" so there is NO "PITTING" OF POINT CONTACTS WHEN POINTS "OPEN". If your points have a "MOUNTAIN" on one point contact and a "PIT" on the other at replacement time, (Most of us!), the condenser is "bad", loose, or just the "wrong value". ACTUAL CAPACITANCE VALUES, if you MEASURE THEM, VARY ALL OVER THE PLACE; MAYBE 100-300%!
In the "OLD DAYS" I found very few condensers from LUCAS or BOSCHE that were "bad" (Open circuit, Short-circuit, or "Leaky") measuring them on an EXPENSIVE Capacitor Test Set, but LOTS of VARIATION in ACTUAL, MEASURED CAPACITANCE! I kept a condenser that had NO "points pitting", and kept all the rest of them in the trunk as "spares" next to my "spare electric fuel pump" and "spare distributor cap/h.v. wiring set", and "plywood square" to set the jack on in muddy/snowy areas.
OLD BILL-67

For anyone who believes your points type MG will run without the ignition capacitor being connected, I suggest you try it.
Barney Gaylord

Hi, Barney - this seems to be a controversial question. I can't say about an MGA engine, but I once (in 1970) drove a '66 Sprite over three miles from my home in West Helena to Turk's Auto Parts and Wrecker Service on the Highway 49 bypass with the condensor in my pocket, to buy a new one. As I recall, it didn't run well at all, and I had to keep the choke pulled out slightly to keep the revs up, but it did make the trip. And then I drove it back home as the replacement condensor had the attaching bracket in the wrong place, and I had to unsolder and move the bracket from the old condensor to the new one.

The particular car in question was in perfect tune, and had an additional noise suppression capacitor on the ignition coil wiring, so this may have had some beneficial effect.

So, I tend to believe that running without a condensor IS possible, although obviously not recommended. Cheers - - Alec
Alec Darnall

I suspect the suppression capacitor on your coil was a poor but barely adequate substitute for the real thing.

My Mallory dual points distributor has the capacitor mounted on the outside near the input terminal. If I disconnect the capacitor while it's running (keeping the coil wire connected) it dies instantly. No pop, no sputter, nothing, just like the ignition was switched off. No chance of a restart either, not a single pop regardless of cranking circumstances. Put the capacitor wire back on and it starts right up on the first crank.

The capacitor is not just for arc suppression at the points. It is a necessary part of the coil circuit. The capacitor allows the input current to the coil to "ring" (high frequency oscillation fading with time) with a peak of about 300 volts when the points break. The 100 to 1 winding ratio in the transformer then gives up to 30,000 volts spark output, which rings in concert with the input. Various coil models may have different windings to provide different output voltage.

Without a capacitor in the circuit, when the points break the inductance of the coil will make a single input voltage spike of about 300 volts, but as the magnetic field collapses there will be no ringing, and the single reverse current "echo" will be at very low voltage, generally of insufficient voltage or duration to give an output spark.
Barney Gaylord

Hi, Barney - you may well be right about the extra capacitance. If I remember correctly, old Turk charged me a buck and a quarter for that condensor, which I thought was outrageous at the time, but glad to have it.

Interesting point - you mentioned the 100-to-1 turns ratio of a modern coil. Some time back I undertook to check that fact, and was very successful by attaching 120VAC from the wall socket to the secondary of several coils, then measuring the voltage across the primary terminals. Voltage readings, in and out, with a Fluke Digital voltmeter satisfied me that the ratio on them all was very slightly under 100-to-1, with the Lucas "Sports" coil reading 97.4-to-1.

Funny thing is that the "Sports" coil had essentially the same ratio as the others (although it was about 50% larger in size), so how could it produce a higher voltage spark? I'd believe a higher current spark - but the voltage is limited by the plug gap size in normal operations, anyway.

Ain't modern advertising wonderful? - - Alec
Alec Darnall

Slightly thicker wire on the input side of the transformer allows for more current in the primary winding. If you check with an ohm meter you should find the primary resistance to be about 3.3 ohms in a stock coil, and maybe 2.7 ohms in the 40KV Lucas Sport Coil. Increased current in the primary may allow it to ring at more like 400 volts peak rather than 300. Higher voltage on the input side would account for higher output voltage.
Barney Gaylord

Ahhhh! Thanks, Barney - I was ignoring the ringing in the primary. Obviously, checking it at 60 cycles for turns ratio is valid, but has absolutely nothing to do with how it operates in-circuit.

Thanks again for opening the shutters, and letting the light in. - - Alec

.

Alec Darnall

This thread was discussed between 29/10/2005 and 12/11/2005

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