912ULS ignition problem

[avidflyer]

Some random thoughts, can you just heat one module at a time, and see if the other one shows dead right after start? Or if you can borrow a module from someone, try yours without heat, and when/if it doesn't start, change to the good borrowed module and see what happens. I imaging you have the 4 pin modules. Another thing to maybe try if you have the ability to start on just one mag (separate mag switches) heat one module, and try to start on the other one, and if it doesn't start on the cold module, try right away on the heated one and see if it starts. Actually thinking about it some more, even if you have the ignition switch with mags 1,2, both, start, you could jury rig a wire to the starter solenoid and still try to start on just one mag by putting the switch on that mag. As far as ground wires go, I had one coil not producing spark, and looked at the grounds, and they all looked fine. I pulled the bad coil off, and the ground was still connected but I missed it. When I pulled the coil toward me, the plastic insulation on the ground terminal broke, and the coil came free. The wire had broken before, and the plastic was all that was holding it in place. When I checked the coil ground wire before I took it off, I pulled on it and thought it was ok, but if I had pulled a bit harder, the plastic would have broke then. I put a new terminal on and was back in buisness. JImChuk

[Slyfox]

well I just went through the mill on my 2008 rotax 912uls. I went out to the airport a couple weeks ago and it wouldn't start. I left it and came back out later in the day and it started. but fluttered for the first few seconds and than ran just fine. after a couple times in the morning of starting it did, but had the flutter. I figured out what was the flutter. One of the mags was not working. I have individual mag switches and I would right after start up do a mag check. one side was not working at all. after the flutter quit that mag was working. so now I know that one was not working for startup. possible the other one is the same but wasn't doing it. I went back out the next day and went through all my ground from battery to firewall forward to the grounds at the cdi modules. I then went home and did some research on the modules. seems they have troubles maybe from heat, maybe from moisture. they start going bad when they won't fire after sitting for a while, you can heat them and they work. after the engine starts they keep working. Now my modules are the 6 pin so I can buy new ones with soft start which is nice for the uls engine. keep in mind the modules are 900 each. ouch! so what I did was buy one module, I figured out which one was which and put the new one on the left side. I got the wire kit to hook the soft start up. I hooked both sides up, but the right side is a nothing without the new module, if some day I get one I just plug it in. so anyway I put in the new module and put that old module in my seat for if I ever need it. Nice to have the new soft start module for starting on the left side, I only have that one on when starting, after a few seconds it goes to full timing and than I turn on the right side. has improved the starting of this engine. Now my thinking is, if the right mag goes all the way out I'll just grab the other module and put it in, than go buy another new module for the right side.

Now to understand how this system works. the modules get voltage from the stator, nothing else. the mag switches put ground to the modules to turn them off, nothing else. if your mag switches are bad, the engine won't turn off. so forget any majic from the switches to turn on the modules other than if the ground is actually not going to the modules. yes, if your switches are bad that engine if turned fast enough with even your master off will start. so that leaves your stator or coils at fault for not starting the engine. most likely the modules. they have had lots of trouble, mainly the 2006 and 7 ones, but lots of them are having troubles.

One more thing I did at the moment with my modules is give them more spacing between them in hopes to have them run a little cooler, I put some spacers in there. hope this helps.

[Av8r3400]

Look to your ground leads for the modules. Possible breaks inside the wire insulation or bad connections.

[Slyfox]

in point no. 6 he said he put heat on his modules and it fired right up. sounds like possible modules. grounds yes yes yes, they have real bad ground, wiring of any kind. check that real good.

[Rodney]

Dave. I have an extra ignition module I can send you for testing if you
might need it. PM me with your contact info

Rodney

[Dave S]

Hi Rodney,

Thank you for your generous offer. Based on several folks who have responded with ideas, I finally contacted Lockwood. They indicated the symptoms I was observing were clearly an indication of a "cut in " issue with the modules (which is apparently not that rare with the vintage of the modules I have); and, they confirmed that often one module goes bad and will not trigger spark so a person does not notice it since the second module will start the engine just fine - then the bad one will cut in when the RPM gets up to 2,000 or so a mag check will be normal once the engine is running. Because the first modules starting RPM failure is masked, if the second develops the same problem it seems like a double fail; but it is just the second one going bad when the first one was already bad. Apparently this affects starting only and not the running condition (which is a relief to know).

Another thing that Lockwood said to try was to cool the modules with ice packs - which baffled me because warming seems to make the darn things work normally. Lo and behold - tried that and the engine fired up and ran normally. Let it sit for a day and it produced no spark again - applied heat and and it ran fine. Why either heating or cooling would make the thing develop spark beats me - the voodoo of semiconductors I guess.

One thing Lockwood indicated was that testing all 8 plugs with a timing light takes the mystery out of the diagnosis. I checked just about everything else first - starting carb operation, battery condition and starting RPM as well as the grounds and P leads (which all were normal).

Based on the input from this group and the confirmation from Lockwood, I have decided to just bite the bullet and get two new modules which will also give a person the new "soft start" feature. BTW - Lockwood indicated that some owners replace one module rather than both and let the other one go since it will run OK once the engine is started; however, I hate to think of being out camping somewhere and rely only on one good module for a start. Also not sure the "soft start" would work with one old style and one new module.

Again I want to thank you for your offer; and, I think I will go with new modules & the soft start.

Sincerely

[Slyfox]

as indicated in my first post. yes they work with one new and one old. but you have to use individual mags switches to make it work(soft start). if you have an ignition switch with the mags as part of , it won't work for you need to switch on the mag that has the soft start, start the engine and wait until the timing goes normal before switching the other mag on. I put the offending module in my seat for if I needed it on a trip. that one does work if you get the idle up to 2000. hope this helps

[Jono]

....They indicated the symptoms I was observing were clearly an indication of a "cut in " issue with the modules (which is apparently not that rare with the vintage of the modules I have); and, they confirmed that often one module goes bad and will not trigger spark so a person does not notice it since the second module will start the engine just fine - then the bad one will cut in when the RPM gets up to 2,000 or so a mag check will be normal once the engine is running. Because the first modules starting RPM failure is masked, if the second develops the same problem it seems like a double fail; but it is just the second one going bad when the first one was already bad. ...

This makes me wonder if one should try starting on opposing modules every once in a while just to check that it has not failed..... Does anybody have compelling reasons for or against?

Cheers

Jono