Sudden Ignition failure

[Chris Edgar]

Engine cut out last night just as I pulled onto the drive.
Won't start now.
Replaced , in turn, coil & condenser... no success.

Low tension circuit seems OK, a test lamp between dizzy & coil lights & goes out when the points open.
Also points spark when manually flicked open.

There is no spark at the plugs, however...
disconnect coil HT lead from the dizzy, put a plug on the end of it & the plug sparks as the engine turns over, so the coil is producing HT

If I then reconnect the HT from the coil to dizzy (cap removed)& connect a lead from the carbon brush to earth...spark.

Seems therefore that the HT is being "lost" between carbon brush & the leads to the cylinders.

So...duff rotor arm? (looks OK).
Any other ideas.

I've ordered a new Dizzy from Accuspark anyway since the current one is very sloppy & tired & the Vacuum unit is broken

[PSL184]

The cheap crappy rotor arms that are around at the moment go open circuit without warning. Change it for the 50 year old one floating around in your boot

[mike.perry]

I assume that it is not a fuel problem?

[Chris Edgar]

Many thanks for the replies...

I "phoned a friend" who was good enough to come around with a spare rotor & cap..
Lo & Behold! It was the rotor arm!

I did not have a spare.
I had checked the fuel, Mike. Plus the complete lack of sparks at the plugs convinced me it was ign.

Looking at the duff rotor, you would not think that there was anything amiss with it at all!

thanks again

Chris

[MarkyB]

The Red super duper ones are said to be OK, the problem with the cheap nasty ones seems to be the rivet that holds them together, and the lack of resistance of the plastic the arms are made from.

[bmcecosse]

" It's 'never' the coil " - repeat 100 times........ And yes - always carry a spare rotor arm - in fact I carry a complete spare know to be working dizzy - and a coil....