912 ULS HARD START, ROUGH RUN

[bitten192]

My 2007 REMOS G3/600 with a 912 ULS (~ 900 hrs) is getting hard to start. After starting. it runs rough for a couple of minutes and then it smooths out and picks up some rpm. That is because it starts on the Left Mag only (with the ignition switch on both mags). I know this because if I switch to the Right Mag on the ignition switch, the engine stops. After a couple of minutes of rough running, the Right Mag starts working and the engine runs fine. Is it time for new ignition modules? How do I diagnosis it? Any ideas? (I’m posting this on REMOS, CT flyer, SPT and ROTAX forums so no need to answer in all places)

[drseti]

Ernie, put a heat gun on the ignition modules, get them nice and toasty, and then try. If it starts smoothly with the ignition modules warmed up, then it's time to replace the failing one.

If it doesn't work any better with heat, you can try cold packs on the ignition modules (it can sometimes go either way). The point is, if one is temperature-sensitive, it is failing. (I'm thinking yours will respond to heat, since things smooth out in a few minutes once the engine warms up a bit.)

While you're at it, you might as well replace both, because (1) if one has failed, the other is about to, and (2) this gives you a chance to upgrade to the new CD ignition modules with the soft-start feature.

Don't forget to also get the ignition-advance Y cable along with the modules. You need to be using the kinds with the 6-pin Molex connectors. Call Rafaela at Lockwood with the part numbers of your existing modules (etched into the black plastic on the sides of the case) and she'll know what you need.

Be prepared to run up a balance on your credit card!

[bitten192]

Thanks Paul. Do you recommend sending then in first to be tested by Lockwood first or just order new ones?

[drseti]

If you do the temperature test, that should be conclusive testing. If you don't mind the downtime, you can have Lockwood bench test them. They used to credit the testing cost toward the price for new modules - you should ask. If you want to upgrade to soft-start regardless, just place your order.

[bitten192]

Are replacing with the CDI Soft Start modules straight forward "plug and play" or is their installation more complicated than just replacing "in kind"?

[drseti]

It's pretty straightforward, but not entirely plug and play. You have to add a Y cable that you order along with the modules. One wire each goes to the Molex connector for each of the two ignition modules (the crimp-on pins should already be installed). You need to install a crimp-on ring lug to the third wire. This connects to the starter solenoid, and advances the spark timing for each of the ignition modules when the starter motor is activated. Other than that, you just replace the old modules with the new ones.

[3Dreaming]

Actually it retards the timing for starting, not advances. You can make up your own harness, but the ends take special crimping tool.

[Wm.Ince]

Paul and Tom,

Good information guys, thank you for the tips.

[drseti]

Actually it retards the timing for starting, not advances.

Aw, heck. I thought I was advanced - turns out I'm just retarded!

[bitten192]

Paul, I'll do the heat gun test and probably order the soft start modules and y cable. Do they come with connection instructions? Is there a procedure in a ROTAX manual?

[drseti]

Do they come with connection instructions? Is there a procedure in a ROTAX manual?

I haven't gotten that far in my research, Ernie, because I have yet to do the mod on my plane (that's a planned project I'm putting off until winter). But perhaps Tom has, and will chime in.

[3Dreaming]

I don't recall any specific instructions, but I think I recall instructions in the HMM for inserting the connectors into the Molex plug. If you have the six pin plugs you just insert one pin into the empty spot on each of the two plugs. Those two wires come together in a jumper type 1/4" blade type connector. Remove the excite wire from the starter solenoid, and plug the harness you just made in place, then connect the original starter excite wire to the jumper blade that you just installed. Make sure you tie those two new wires up where they won't get pinched or abraded, otherwise you can have a short to ground when you try an start the airplane. Don't ask me how I know.

[ShawnM]

I went through this a few years ago and it's very easy to do. Here's a link to download the Rotax service instruction: SI-912-028

https://rotax-docs.secure.force.com/Doc ... sPdf=false

As Paul stated, make sure you have A LOT of room on your credit card before you call Rafaela.

[bitten192]

Thanks guys for all the info. I'll take out a second mortgage and buy some new modules.

[bitten192]

SI-912-028 says I have a type "C" engine which requires replacing the Flywheel Hub. Is there any advantage replacing the modules with the easy start modules and not replacing the hub. I would rather wait until gearbox inspection time to replace the hub Thoughts?