LightSpeed Ignition problem

[Daveembry]

Spark plug gap for the CC340 engine is .032-.040 per the CC11-160 AMM section 6.3.18 pg 2

http://www.cubcrafters.com/pdfs/ccss/cc11-160amm.pdf

I know this is an old post so the link isn't good any longer......here is from the Lightspeed Manual:

LSE Spark Plug Gap SpecificationsEngines normally timed at 25 degrees BTDC:These are typically engines with compression ratios less than 8.7:1. Gap spark plugsfired by the CDI to .032", max wear limit is .040".

Engines normally timed at 20 degrees BTDC:These are usually engines with compression ratios of 8.7:1 or higher. Gap sparkplugs fired by the CDI to .026", max wear limit is .035".

So our engines are 25 degrees but 9:1.....so which to use? I guess we will go with the 25 degree setting and start gap at .032 but check it and the max with wear is .040.

[seastar]

I had a complete failure of my left Lightspeed module that Lightspeed said was probably caused by a backfire because there is no restrictor in the pressure sensor line.
I know Pete disagrees with this.
I have always doubted that cause also but that's what Lightspeed said.
That dosent sound like your partial failure but who knows.
Lightspeed replaced the module at no charge.
Of course I paid shipping and mechanics charges.
Seastar

[40m]

I had a complete failure of my left Lightspeed module that Lightspeed said was probably caused by a backfire because there is no restrictor in the pressure sensor line.
I know Pete disagrees with this.
I have always doubted that cause also but that's what Lightspeed said.
That dosent sound like your partial failure but who knows.
Lightspeed replaced the module at no charge.
Of course I paid shipping and mechanics charges.
Seastar

How old was the unit they replaced and did you put a restrictor in place?

[seastar]

About 150 hours old, as I remember.
No restrictor.
Pete pointed out that the Lightspeed installation manual did not call for one.
Its been OK since. No backfires though. I am very careful when switching ignitions.
Seastar

[Daveembry]

On the latest build I ran into an ignition problem and made a post in my thread on Building the EX3 - Tips & Hints thread

http://forum.cubcrafters.com/showthr...Tips-amp-Hints

and thought I would just copy and paste what I posted there onto this thread in case others had a similar problem. It's good in that it somewhat explains how the system works so you can troubleshoot it or recognize a problem.

Ignition system and mini-sensor. This was a pretty interesting situation. Back in the post when installing the G3X wiring and the wiring harness in general, I tested almost every wire going “somewhere” light lights, trim motor, etc. but as mentioned before.......not the trim sensor and I didn’t ever test the ignition system other than to test the wiring per the instructions on the operation of the switch, backup battery systems, etc. but I didn’t think of .......or know of a way to check to see that the mini-sensors worked...........and I wished I had..........and I will in the future.

Here’s what happened:

On the first engine run-up the engine fired right up and ran fine. I did a quick ignition check........on BOTH......ran fine. On LEFT.......ran fine. On RIGHT..........bam.........really bad miss and huge drop in rpm’s.

I switched to LEFT and looked at EGT’s and all showing green but when I switched to RIGHT......... cylinders 3 & 4 EGT’s dropped off to nothing. Here’s the procedure I used to work out the problem.

Understanding the ignition system, here is how it works. The RIGHT ignition box has 2 cables going to 2 coils at the bottom side of the engine and this box fires the BOTTOM spark plugs in the engine. The LEFT box goes to the 2 upper coils and fires the TOP spark plugs.

So on the 2 bottom coils that are controlled by the RIGHT box, the pilot right side box controls bottom cylinders 3 & 4, which are the ones I had a problem with so I first suspected a coil problem so I swapped that coil out with the coil on the bottom, left side (that controls cylinders 1 & 2) and the problem did NOT move to cylinders 1 & 2 but stayed with 3 & 4........so this eliminated that it was a coil problem.

When I experience a problem, it’s seems it’s usually the simplest thing that causes it so I always look at the simplest things first before going to the hardest. In this case I'll test..... the coil, spark plugs, spark plug wires, ignition wires, mini-sensors and lastly........the ignition box.

Coil eliminated so i next checked the spark plugs (fat chance that 2 plugs were fouled at the same time ....right?)and they looked fine but I went ahead and put 2 new ones in anyway.

Next I did a continuity check on the spark plug wires going to these 2 cylinders (fat chance that 2 spark plug wires were bad at the same time.....right?). All good.

Next I removed the right, forward interior panel to expose the ignition boxes and I had previously labeled each box as RIGHT and LEFT by writing this directly on the boxes with a sharpie. The left side box was the LEFT side box so I removed the right side RIGHT ignition box ignition wires (BNC connectors and on the forward side of the box) and did a continuity check with the positive side of the connector at the coil (blue connnector attached to the center wire of the cable) and the center of the BNC connector and the negative (yellow connector) with the outside of the BNC connector. I really thought I might find the problem here where I had installed the connectors but it was all good.

Next I double checked the mini-sensors I installed at the flywheel to be sure the gap was correct. The tolerance is .030-.060 from the flywheel being sure it stays parallel to the flywheel across the mini-sensor. They tell me that the closer to the minimum gap the better, so I used .032. All good.

Next....... crap.......guess it’s the box and it doesn’t look like fun removing that bracket. Mitch and CC was great and overnighted me another box and instead of actually removing the existing boxes, I just attached the connectors to the new box temporarily to test it. I didn’t bother removing and installing the yellow manifold pressure lines from the existing box to the new box because it wouldn’t affect the engine running.........it only affects the engine timing.NOPE.....not the box!!!! NOW WHAT?

OK....emails out to Klaus who owns Lightspeed. It was amazing.....it was a Saturday and i didn't expect to hear from him at all.....much less on a Saturday.....but within an hour or so he replied and said..... “our boxes and mini-sensors never fail” and he suggested running the tests listed in the Lightspeed manual that comes with the system (and from CC). I looked them up and pulled the INPUT cable from the back of the box and checked the pins listed to see if power was coming into the box from the aircraft wiring harness........... ALL GOOD!

OK....NOW WHAT?

Has to be a mini-sensor right? But Klaus says they never fail. Only problem is I know a guy who did have one bad so I knew they could be bad. If you recall, there are 2 mini-sensors installed 180 degrees apart from each other up behind the flywheel.........1 for each for the LEFT and RIGHT ignition boxes. The sensor on the RIGHT side of the engine is for the RIGHT box (and my problem area). On the aft side of the flywheel there is a plate that is installed that has magnets in it. These magnets are picked up by the min-sensors as the engine rotates and this signal passes from the sensors to the ignition box which decides when to send a signal to the coils to fire.....which then goes through the spark plug wires to the spark plugs ......and the engine fires. This timing of the firing is changed by the ignition boxes and the changes are based on a multitude of data.

Digging into it more, I discover that each “mini-sensor” unit is actually comprised of 2 sensors in the housing.......1 that is for the cylinder 3&4 coil and the other for cylinder 1 & 2 coil. So my 1 & 2 side of the sensor is working but the 3 & 4 side is not???

Once again Cubcrafters comes through and overnights me a new sensor to try (even though they never fail........).I’ve got the new sensor and see that the cable is long enough that I can install it on the right side of the engine and just run the cable on the outside of the plane to the box inside to just test it before actually going though the hassle of getting it thought the firewall clamshell, etc.

So I remove the existing connector from the right sensor where it goes into the ignition box. I’m inspecting the wires going into the connector and see that there are 2 wires coming from the sensor into the connector, no doubt 1 from each side of the mini-sensor so 1 is for that 3 & 4 coil and the other for the 1 & 2. Hmmmmmm.......what if......

Yep.....with my magnifying glass, I look very closely at the solder connections Lightspeed has made where the wires attach to the connector.....the pins are side by side and looking closely, I see a bit of solder has bridged the 2 pins and I’m sure that shouldn’t be. A soldering iron to melt the solder and a small piece of sandpaper between the pins and it’s all back together and working great! What a relief but it has taken me almost a week to get this one sorted out.

SO......... in keeping with my #3 item on the problem solving list above on how to deal with problems..........how can I test this in the future when installing the engine/wiring? Believe me........I DID NOT WANT TO HAVE TO CHANGE OUT AN IGNITION BOX after having looked up there and seeing how hard it was going to be to access the bolts/nuts/clamps. I will also change the way I install the ignition boxes in the future to make it easier if I ever have to (and will discuss that later below).

So from now on, I will test the mini-sensors/ignition boxes, etc. Looking at the Lightspeed manual, there is a test you can do that will show if a signal is passing from the sensors to the box when a magnet passes by it. i think this can be done while wiring the units and before installing the boot cowl. Essentially, you remove the input connector from the box that is coming from the sensor. The manual shows which pins to attach a meter to and when you pass a magnet (maybe a magnetic pickup tool?) by the sensor, you will see voltage show up. CC has the power wires, etc. they have installed into this connector that you have to connect into the wiring harness, so be sure when you test that those wires are connected to the wiring harness and that you have master switch on and battery power of course.

Another test of the system once you have the engine installed (prop can be on or off)......either remove all the spark plugs (especially if no prop on and you want to turn the engine over by hand using the flywheel) or remove the spark plug wires from the spark plugs. Also remove the spark plug wires from the coils. With the master switch ON and the ignition switch on BOTH, turn the flywheel around quickly and you should see the 4 coils “snap” or fire/spark each time the flywheel magnets pass the sensors. All 4 should work.

[cityrancher]

Thanks for a great report of your findings.

[seastar]

I wonder how Gystavo solved his problem and what had failed?
Seastar