No Spark

[Peted7202]

I am bench testing my overhauled engine. I am attempting to prove the ignition system without starting the engine. Currently I have no spark.

The points, coil and condenser are new. Coil test as healthy 3.5 & 7000 ohms.

So I have a 12v supply via a switch to the coil positive terminal - proved.
I have 12v to and across the points from the coil negative terminal when points are closed.
If I open the points whilst powered there is no spark from the coil HT lead to the engine body.

There is continuity from the coil to the HT lead (15kohms)

The points wiring is shown in photo.

Any advice please.

[geoberni]

Have you earthed the Engine back to the battery?
All very well having the Low Tension side of the Coil connected, but the HT Spark has to get back to the battery...

[Peted7202]

Yes earth connected and proved.

[geoberni]

Yes earth connected and proved.

A short on the assembly of the points?

[Peted7202]

Yes earth connected and proved.

A short on the assembly of the points?

Thanks. Here's are close ups of the points setup. Bench test of points assembly.

Continuity between baseplate/spring arm and tabs/CB with points closed.

Nothing when points opened.

[geoberni]

Hang about!

You said

I have 12v to and across the points from the coil negative terminal when points are closed.

Which contradicts the preceding statement

So I have a 12v supply via a switch to the coil positive terminal - proved.

When the Points are CLOSED, there should be ZERO Volts across the Points, because you have continuity of the circuit.

Now is this just the poor way you've phrased it, or have you actually got 12v across the closed points?

If they're new Points, have you cleaned the preservative from the surfaces?

[Peted7202]

Poor phrasing.

I have removed and cleaned all connections and points and I now have a spark. It's difficult to see why no spark before when all the connections were clean and dry. So the points may have been the culprit.

Thanks for your support.

[geoberni]

Poor phrasing.

I have removed and cleaned all connections and points and I now have a spark. It's difficult to see why no spark before when all the connections were clean and dry. So the points may have been the culprit.

Thanks for your support.

Glad you sorted it.
Many years ago, circa 1978, when I was in the RAF as a young aircraft electrical technician, I was working a snag along with a young mechanic and he checked the fuse, declaring it Good. We spent another 2 hours working the snag before, totally stumped at why there was no power where it was needed, I started afresh and checked the fuse myself. It had blown. Fuse replace and that aircraft never blew the fuse again as far as I recollect, so just a spurious fault.
We're still good friends and every few years the subject of how to use a multi-meter comes up, usually over a few beers...