912 ULS start issue Newbie

Food for thought:

Was this a problem before mechanics worked on it? Is this a high wing and if so have you been shutting off the fuel when not in use? Some have flooded carbs because they don't shut off the fuel in a high wing. It's possible your carbs are flooded and these may need to be             re-checked. Was this happening before or after the carbs were done? You say battery is charged to full. What does the voltage drop to when you try and start it? It could have a bad cell. try a jump start if the battery drops into the 11 volt range. Most likely not plugs because even if there were 1-2 bad ones it would still start. Is it possible to be the trigger coil gaps in the back. Not likely. Even if one was out of spec it should run just not be smooth during a mag check.

Let's try one troubleshoot here. get a one gallon bag of ice. Don't pack it full just enough so it lays fairly flat. Now go wrap this around the two ignition modules on top and sides. Let this sit for 30 minutes and then try a start. Full choke and crack the throttle about 1cm. Now try a start. If it starts right up replace the modules.

Great thanks Roger that's good gen, I will do what you suggest with the modules and check the voltage. It is indeed a high wing and we had issues a while ago so a NRV was placed to stop the fuel doing as we suggest as that was def an issue a year or so ago, it may well be still connected to the fuel issue so I will double check those to. Many thanks!

Hi Stuart,

Remove a all of the top plugs (easier cranking and will not start for safety), rest the body of the plugs on the metal of the engine, switch the ignitions on and crank it. You should see a nice blue spark between the electrodes on the plugs. If not, that's your problem.

You will need a multimeter to measure the resistance of the kill switches. I would just disconnect the connector at the ignition module and measure it from there. If both kill switch lines measure shorted with the switch in either position then you need to fix them. It could be the switches (unlikely) or the wiring.

If that all checks out OK then you need to check the generator coils that supply the ignitions using a multimeter.

If you have a spark but still not starting then I would check the fuel level in the carb float bowls. If there's no fuel there you need to investigate the stop cock, pump, hoses, etc.

If there is fuel in the carb bowls then you will need to investigate the choke mechanism. Let us know what you find.

Cheers Kevin, I will do that and let you chaps know.

Many thanks,

Stu

Hi Stuart,

 I always like ruling in and out the most common cause, cheap and easy things first. Don't throw money at it and save the PITA parts to get to until other items are ruled out. DO a,b,c,d things in order of a possible cause because if you jump from b to m it might just have been c.