Qualcast Suffolk Punch 35s Problem

[manuel]

My first post. Hope this is the correct section to post this question

 

I have a Qualcast Suffolk Punch 35s electronic ignition lawn mower that as be cutting my lawns for a long time with no problems, just a service at regular intervals.

 

But the other day while trying to start the lawnmower there was a bang which I believe to have been a back fire? After then the mower would not start

 

I checked the fuel and the carburettor that was ok and the compression

But unable to produce a spark at the spark plug

Being a electrical engineer I checked the cut off lead and the continuity of the ht lead all ok

 

Replaced the spark plug with a new one as there was no continuity on the centre electrode

Also replaced the electronic module 3 pole unit inside the flywheel with a new one

Which as all new HT and trip wires cables attached

And still no spark also removed the spark plug cap which from the reading as a 10k ohm suppressor built-in and connected the lead directly to the plug

Inside the flywheel the electronic module is screwed in place with no adjustment and the flywheel with the magnets build in are keyed to the shaft so there is no adjustment

 

There is a small voltage at the plug but nowhere a voltage to create a spark also turned the motor over with a portable drill with the spark plug removed and the thread connected to the frame

 

Has anyone any suggestions what maybe wrong with the mower that’s stopping it sparking at the plug

[cornish wood burner]

Flywheel key sheared ?

[cornish wood burner]

Flywheel key sheared ?

 

Sorry it was late and I never read past the backfire. New modules have been known to be faulty but best get advice from someone familiar with the machine

[mikerecike]

Is that the tecumseh engine?

[mikerecike]

If its the ignition coil youve replaced what happens sparkwise if you pull it over with kill wire removed from coil?

[manuel]

The module is encapsulated with only two wires coming out of the module the trip wire and the HT wire I have also tried a second module here is no coil that came be seen only the three metal parts coming out of the module there are there to pick up the magnetic field when the magnet in the fly wheel passes the module and with a bit of electronics inside and a transformer increase the voltage when the magnetic field collapses and in the last few days have tried a second module and did try with the trip wire disconnected because that seem to be a common problem that is over looked

 

But sorry to say no spark

[manuel]

I am not sure but it maybe a Briggs and Stratton Electronic ignition model 98cc

[Agi-Smash]

Think i know the engine youre on about. Will try and post some pictures tomorrow as i have several in bits. Does that have a cast iron or aluminium flywheel?

[manuel]

aluminium flywheel with imbedded magnets it the one that needs the 3 pole electronic ignition module

[GardenKit]

As a matter of interest, how are you testing for a spark? Are you quite sure you do not have one.

 

If the coil is good and the flywheel magnets are strong you should have a spark. It is really quite a simple system.

 

Your problem may be elsewhere, such as valves.