Why not invest in an electronic ignition system such as a Lumenition or something similar? You'll benefit from the advantages of having a bigger and more reliable HT spark, and you'll never have to worry about replacing the contact breaker points or condenser ever again.

Wont be available here, since there is no one who would buy such a thing, especially for a car with zero market value.

I do, however, have a Maplins transistor assistance kit, bought in the UK before they went bust.'

Ive been putting off building it, mostly because my soldering is poor.

I tried testing an ignition capacitor like that on an old motorbike that had an intermittent spark, it too seemed fine. I then changed everything else in the system to no avail. I jury rigged an external capacitor and cured it. I compared the old and new capacitors electrically, they both gave identical results. I can only assume it was breaking down when in circuit.

All ignition condensers are exactly the same. It's job is to reduce the current crossing the points. They only differ in their shape and size. They all connect between coil negative and earth, and they can only fail in one of two ways.

1. Open Circuit. The current crossing the points will be at maximum and the points would arc and burn very quickly.

2. Short Circuit. Because the coil negative would be permanently grounded there would be no HT spark at all.

All ignition condensers are exactly the same. It's job is to reduce the current crossing the points

I understood they control the CR time of the decay in the coil. That also reduces arcing of the points.

My point was mainly to make clear that any condenser will do. It does not have to be fitted inside the distributor. It just needs to connect to the ignition coil negative terminal and earth, so it doesn't matter how big or small it is, or what it looks like. It'll do the job it's required to do just the same. So trying to source exactly the right replacement part for this particular vehicle (or any other) is not necessary.

Finished off with some contact cleaner on an earbud and put them back on. Seems to run OK, though I may not have set the gap correctly.

The distributor faces backwards and I couldn't see if the heel was on the peak of the cam, which I suppose is required to set the gap. Tried it with my recently bought cheapo webcam but the LEDs on it have stopped working and the light wasn't good enough. Might try it again with a mirror later.

The CB20, (this is a CB22 which I'm assuming is the same) manual says to set the heel gap rather than the points gap, (perhaps to avoid contact arm flexing?) but I was at the timing/TDC mark (not sure which it is) for static timing so this didn't seem appropriate.

They then tell you to use a dwell meter once its running, but I don't have one, and there will be very few people on the ROC who have ever heard of one.

I used a timing light and advanced it to about the middle of the upper half of the timing window, probably about another 5 degrees. Revs rose a bit when I did this.

Edited by edlithgow on 05/04/2020 at 06:37

Thanks for your reply.

Re A dwell meter is the most accurate way of setting the points I daresay it is, but, as I said above, I don't have one, and am unlikely to be able to get one here.

Possibly a non-automotive meter that does duty cycle (mine doesn't) could be obtained here and used for this purpose.

I have to say I'm not keen on using my questionable assessment of "pinking" (do you mean detonation, pre-ignition, or both/either?) onset as a tuning method, and would be willing to accept a slightly sub-optimal tune to avoid that danger zone.

I took most of the "extra" advance off that I'd added previously because of that concern, before I took it for a short test drive. There seemed to be more vibration than previously, though I wouldn't describe it as an obvious misfire. Driving, performance was poor and there was some fairly marked hesitation, though it remained drivable, which it wasn't before.

I dunno if the points cleanup was partly inneffective, I got the gap/timing wrong, its The Return of The Vacuum Leak, something else, or all of the above

iI'll re-do the timing and paint some more sunflower oil on the intake manifold and carb.

Might be ready for another test run thur/fri but I'll have to do some work first..

Edited by edlithgow on 05/04/2020 at 11:43

Some circumstantial evidence that a vacuum leak may be part of the problem:-

The last (much worse but give this one time) rough running episode got better after I painted the intake manifold and carburettor with multiple coats of sunflower oil, suggesting it had sealed an undetected leak. Sunflower oil polymerises oxidatively to form a plastic-like coating.

A few years ago I did a wee experiment looking at thermal degradation of sunflower oil with simple chromatography, and put the leftover oil (which had been heated in an aluminium custard pie dish) in a cupboard, where it set almost hard.

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However, after a long time (maybe a year or so) it re-liquified, and later still, re-solidified.

The chemistry involved is probably rather complex, but, whatever it is, it doesn’t seem to happen where the sunflower oil is used as a binder for aluminium abraded in situ, as on my brake drums, where the coating seems stable. I assume the metal (iron and/or aluminium) somehow stabilises the oil.

I noted an oil stain under the car but couldn’t see a leak, and assumed it was from another vehicle. I now suspect the vegetable oil had re-liquified and run off the intake manifold, re exposing a vacuum leak.

If this is true, my options seem to be

(a) Re-treat it, perhaps mixing some ground aluminium into the re-applied oil.

(b) Use some other sealant, such as varnish, laquer, or PVA. The existing vegetable oil may inhibit adhesion though.

Edited by edlithgow on 07/04/2020 at 09:57

There's something I half recall from my dim and distant past.

When looking for an inlet manifold leak, use soapy water on the suspected area and turn the engine backwards. I suppose the theory being pressure will be built up.

Never tried it and don't know if it works.

Reverse lateral thinking. Like it

Quite difficult to turn the engine over fast enough by hand though, and would involve some multi-tasking solo.

Sealing off the air intake fairly tightly (a plug held down by the air cleaner wing nut, maybe) should get around that, though you'd have to be a bit careful you didn;t astually cause a leak, and I suppose the crankcase ventilation system would have to be blocked off too..

Certainly seems to have potential, thanks

Or you could spray carburettor cleaner, easy start or brake cleaner around the inlet manifold with the engine idling. Any change in engine note would mean you have a vacuum leak, and it'll be easy to locate. If there is no change then there is no leak. Don't forget too that manifold vacuum is at its highest at engine idle, and therefore its effect on the engine running is most severe at idle.

Any breach in the manifold gasket or base of the carburetor won't show much, if at all when the throttle is open. This is because there is no manifold vacuum when the throttle is open. Air will be drawn via the easier route, and that's through the open throttle valve. Manifold vacuum is at its highest when the throttle is closed and the engine speed is decreasing, ie throttling off. And that's when the effect of any leak will be most obvious. And of course when the engine is idling. Don't expect to find it easy to locate a vacuum leak when the engine speed is above idle and the throttle open.

I re-did the points gap with the points arm on the peak of the cam, (which I suspect I didn’t get right last time. Awkward because it faces backward, and I had an audience), set the static timing with a test light, then set the dynamic timing with a timing light, advancing it about 3 degrees from the mark.

Better but not great. Thought it might be worth checking the inlet manifold vacuum at idle, as suggested by Railroad above.

. There’s a capped port on the inlet manifold which I assume is for such diagnostic use. Last used it checking (as recommended somewhere on't nyet) for exhaust blockage, but I couldn’t interpret the results.

The cap was missing. Thinks: “That’d be a vacuum leak, then”

One of the wee red plastic pips you get on the sharp end of wire-green-plastic-coated-hangars was a perfect fit.

(Vacuum was about 510 mm/20 ins Hg, so in the “normal” range)

Now running nicely almost all the time, based on a couple of hours test run into the mountains, but with very infrequent hesitation under acceleration.

Edited by edlithgow on 11/04/2020 at 12:18

Thanks

Can't remember my original reference for this re exhaust restriction though I could probably dig it out. Also can't remember what my problem was with interpretation, but it could be related to,

" If the vacuum drops off as the engine speed is increased then suspect an exhaust restriction."

since that sounds like normal vacuum-is highest-at -dle behaviour as the thrittle progressively stops throttling.

In order to get something that made sense (to me) I made up a spacer with a port in it to put between two exhaust sections and measured the exhaust back pressure directly,

Meanwhile, nice day so another run, Stopped after about 5 mins to answer the phone and had great difficulty re-starting,

So back to the drawing board, or maybe the ouija board..

Thanks. I'll bear that in mind.

Don't remember much of a gasket there from when I took the carb off, so it would seem a possibility, though its dark now so Ill check later.

Would thick polythene be a suitable material?

Did have some heavy lay flat irrigation hose material, but might have lost or chucked it. Could probably scrounge up some more though.

Meanwhile I noted that my improvised vacuum gauge port cap was missing, so my money is cfurrently on that.

I'm guessing that the manifold is getting transient positive pressure incidents (though I dunno what might cause them) which blew the cap off. Fortunately I have a few coat hangers.

I put a document clip to bridge between the adjacent brake servo hose and this port, and took it for another run. It stayed on and remained drivable and startable.

I believe its supposed to be an economy aid too, if you drive to minimise the vacuum

I would have thought you'd drive for maximum vacuum for economy.

Going by what I recall from vacuum gauges back in the (cough) '60s, the green area was maximum vacuum.

Although I believe there is a train of thought that it's more economical to accelerate briskly to cruising speed and then back off, rather than slowly accelerate to cruising speed.

I suppose another way to get positive inlet manifold pressure would be to roll backwards in gear, engine off.

I did stop on a slight hill but I dont THINK I did that, though I suppose it wouldn't take much.

I think I normally coast to a halt in neutral, which would prevent this.

I suppose another way to get positive inlet manifold pressure would be to roll backwards in gear, engine off

Do it with the bonnet up and someone spraying soapy water while looking for bubbles?

Yes, odd how this came up again. Everything is connected

From a practical point of view it'd be a bit difficult to arrange solo, plus I may not need to, since the open port does explain the vacuum leak. Of course there may well be others.

I rigged up the gauge to where I can see it through the windscreen and will probably test drive with it tommorrow. May take it in for the 6 month inspection, though the gauge is probably technically an illegal modification.

Re vacuum leaks, I may have missed it in the thread but....

Have you checked the...

Vacuum brake servo?

Distributor vacuum advance?

And some cards used to have an air admittance valve to stop running on after switch off.

Good luck!

There are actually 2 vacuum advances on the distributor. One of them advances the ignition when I pull a vacuum on it with a syringe, the other doesnt.

That one is connected to the horribly complex and undocumented anti-pollution gear. I disconnected and blanked of this snake pit of vacuum lines and gizmos (which I dont understand) apart from the (main?) vacuum advance, as work-around to running problems about 2 years ago, when I stripped the carb.

I labelled them, but the labels have fallen off, so I probably couldn’t re-instate them if I wanted to.

I believe this is a Taiwan-only car, so of course its undocumented, but I have manuals for similar related Daihatsu cars, which have a variety of (entirely unexplained) vacuum line diagrams for various markets, none of which is quite the same as this one.

I tried to understand it once and it gave me a headache, plus my choke stopped working, so I took it all off, and I don’t want to think about it ever again.

Of course the fact that its blanked off doesn't necessarily mean it isnt leaking.