Rustoration

[RogerT]

Thanks so much for your help, both of you. Off to do a bit of plastering for my son, then I'll pop to the motor factors while they are still open. Fingers crossed with them otherwise it'll be minispares.

Your time and advice is much appreciated!

[RogerT]

Thinking again about electrical pathways, and what I see on mine, I get regular sparking from the distributor end of the coil-to-distributor lead when it’s held to the engine. The path taken from there is down the carbon brush to the top of the rotor arm, along the rotor arm to whichever distributor cap pin it is aligned with, and out along the spark plug lead to the spark plug. Am I right?

So I have what seems to be the spark generated correctly at the coil which suggests the points are ok, as I see the spark having exited the coil, so the points are working correctly?

But you’re right, I should just get it all to save time.

[937carrera]

The ignition system has what used to be referred to as a low tension and high tension circuit. The coil has both components.

The points use the LT side. When the spark jumps across the points, the collapse of the LT circuit ~(12v) in the coil causes the field in the HT circuit (say 7000 V) to collapse, the HT current goes along the king lead to the dizzy, down through the carbon connector to the top of the rotor arm and then to the connector for one of the plug leads.

The fact that the king lead is sparking when you tested it indicates that the HT circuit is fine, so the issue is the LT side.

At least that's what I remember

Unless the grease on the top of the rotor arm is actually preventing the spark travelling across the rotor arm. 2 minute check before you spend money

Do the spark across the points test and you know the LT side of the coil is fine too

[937carrera]

or read this

https://www.minimania.com/Troubleshooting_Lucas_Points

[RogerT]

Yup, I have a spark across the points. Just a wee one, but that’s what we would expect from the low tension side? And that confirms why I am seeing the regular sparking from the centre lead, it’s getting triggered correctly. I’ll look closely at the cap.

[RogerT]

Factors will have cap and arm on Monday, £10. Meantime I’ll try cleaning mine.

[937carrera]

LT side seems fine, including condenser. Just remembered you can simply open the points with a screwdriver, no need to turn engine, bit of brain fade, too used to crank position sensors etc.

Just cap and rotor arm left I think, you're on test 7 in the link I posted.

[937carrera]

OK, no good for your buyer coming tomorrow though.

I'd also double check static timing, just in case the dizzy has moved, and another plug for the test, just in case the plug you tested with has gone faulty. Unlikely, but worth ruling out.

[RogerT]

[bigbadbob76]

The fact that the king lead is sparking when you tested it indicates that the HT circuit is fine, so the issue is the LT side.

Unless the grease on the top of the rotor arm is actually preventing the spark travelling across the rotor arm.

If the king lead is sparking, surely all is well up to the dizzy, Ht and Lt ok.
The grease could be the problem but I'd just change the dizzy cap and rotor arm.

[937carrera]

LT part not necessarily fine. The test energises the coil until there is sufficient potential in the HT winding of the coil to leap the 1/8" gap, field collapses and process begins again. I think, anyway it's test 1 in the diagnostic link I posted above.

or maybe you're right BBB, it's just what I remember from nearly 40 years ago

[RogerT]

Woohoo!! Mini saga over! (I know it’s not really a saga but it felt like one to this ignorant old man). New cap and rotor, started first turn of the engine.

Thanks all, I’ll try and sell it again, and buy metal bits!

[937carrera]

Back on the rust removal / meta bashing then

[bigbadbob76]

Och, there was nothing really wrong with it. it just wasn't feeling the love.
Glad it's sorted now.

[RogerT]

Looking closely at my bench grinder...


...the doobry at the side is a ...

Not sure it’ll go up to the angle for a spot weld drill, but worth a fiddle.

The van, spent bleeding ages fettling the edge of the floor. I think the majority of my learning curve at present is how not to do things!!

Ended up with this though, fits not too bad.




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