Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Thanks Nick for the welcome.

I am now certain that the issue is with the sealed electronic ignition box.

All wiring is correct and secure, the cleaned spark plug is not shorting out and the issue has developed since the engine first stopped running. The spark, such as it was got weaker and has now stopped altogether. I am going to make a new ignition unit myself using Jan Ridders idea of using a cheap sparking gas lighter unit. These are very cheap and he uses them on all of his petrol engines. I have already sent for a handful of electronic components which are needed to alter the gas lighter unit.I will be using a thyristor to switch the LT current in the coil. It will take the place of contact points in a traditional old fashioned ignition system and I am hoping that the little magnetic sensor on the engine as supplied, is a simple reed switch. If not, I have some of them anyway so can substitute if need be. (**) I suppose the whole thing will cost about £12 so - way cheaper than trying to source another unit from China and far quicker - -  - if all goes well, that is. Also - if this new one gives up the ghost, I can make another for little money.   

** EDIT  12 HOURS LATER

- I checked this morning with a multimeter. The position adjustable, black sensor which triggers the spark on the engine at the flywheel as supplied,  is indeed a reed switch. It is naturally open circuit and closes when the neodymium magnet comes in close proximity. I am pretty sure that will work to trigger the spark on the Jan Ridders circuit, just as it did on the original design. 

Here is a link to Jan Ridders page on the circuit. Click for English version of the page unless you read Dutch:

http://www.ridders.nu/Webpaginas/pagina_blokker_vonkcircuit/blokker_crcuit_frameset.htm