Ignition mystery Lightspeed Plasma ll

Recently started my RV-7A for the first time and experienced a small glitch. Although the aircraft started no problems when I tried switching between right and left ignitions I noticed a problem, the left ignition, a magneto ran fine however when I switched over to the right side (lightspeed plasma ll) the engine started to quit . On (both) the engine ran fine but did not show any RPM drop from the left setting. Did some trouble shooting and tested the ignition with the engine stopped and manually turning the prop and checking for sparks from the right ignition (Lightspeed) and guess what! sparks were visible in both (right) and (both) settings on my Spruce ignition switch. What the heck, with the engine shut down my Lightspeed works but with the engine running apparently no joy. One note is that my EIS4000 displays RPM on the tach indicator only on the both setting and I get my tach signal from the Lightspeed unit! Anyone had anything similiar or have suggestions what to track down first? All suggestions welcome.

Mark Mercier
RV-7A C-GQRV reserved
Vancouver BC
ECI O-360

My bet is that the Lightspeed is timed 180 degrees off. It doesn't run very well if you light the plugs BBDC.

You have two coils, one for each opposing cylinder pair. You also have two RG45 leads from the control box, each with two spade connectors. Swap the RG45 leads between coils and give it a try.

By the way, about that RG45. It has a very low temperature limit. The white plastic insulator can get soft and let the center conductor migrate through the insulator at cable bends, which shorts the center conductor to the braid. If Lightspeed still delivers with RG45 cables, make some new ones from RG400 or similar.

Dan

Check your phasing (previous poster mentioned this), and also check your connections at the coils. Early on I had an issue with intermittent ignition on my LSE in flight, but it was fine on the ground, running or not. Strain relief on the coil wires & connections...100% builder error (me).

By and large what I see out there is NOT ENOUGH strain relief on the coil connections. RG400 (or RG58) and crimped fast-on connectors don't really get along all that well imho. There's not enough support of the center conductor's insulator, since it doesn't fully insert into the fast-on connector. That, and many builders I see allow too much strain on these wires anyway (myself included, until I learned better).

I'm not saying this is the cause of your issue, but it's definitely something to check. When I checked mine, a wire all but broke off at the coil connector. It made enough contact to run on the ground, but not so well in flight...

This is such a simple thing to do right (meaning zero strain on those wires, and more robust connections/crimps/strain relief). It's also easy to miss if you "just follow the directions."

As far as I can tell, this is the only "mechanical" weak spot of the LSE ignition system. Once you get this licked, it should be smooth sailing.

I know two people who have been stumped with the gap on the hall effect sensor. Apparently that gap is quite precise...

<<There's not enough support of the center conductor's insulator, since it doesn't fully insert into the fast-on connector.>>

Agree for sure. I'm a big fan of heavy wall adhesive heat shrink over the top of such connections. The combination of heavy wall and thermoset glue really toughens otherwise poorly supported crimp connections.

My only Lightspeed problem was also at those female spade terminals. One of them was not clamping the coil spade as tight as it should. The cable carries HV, not 12V, and the terminal arced and burned slightly at the spade/female terminal interface. Showed as rough running during a "mag" check.

The other TC Dan <g>

DanH said:

By the way, about that RG45. It has a very low temperature limit. The white plastic insulator can get soft and let the center conductor migrate through the insulator at cable bends, which shorts the center conductor to the braid. If Lightspeed still delivers with RG45 cables, make some new ones from RG400 or similar.

Dan

Click to expand...

Something might have changed in the new system, so depending on how old yours is will make a difference. I believe Klaus uses only RG400 now and it uses "telfon" as the dielectric and not just common plastic. That should have a much better heat resistance than plastic.

Lightspeed problem

Recently, I have had an occasional problem with my lightspeed ignition. During cruise flight the lightspeed RPM drops to 1000 rpm and I get engine roughness. When I turn the magneto side off the engine still runs but seems like it maybe running on only a couple cylinders. Has anyone had the same problem? I am thinking it maybe a coil problem.. Maybe a connector at the coil or at the box. Anyone have any ideas?

Thanks,

Patrick
RV8, O-320

Patrick...read my last reply. You probably have a bum connection at one of the coils.

Another possability

teaguy said:

Did some trouble shooting and tested the ignition with the engine stopped and manually turning the prop and checking for sparks from the right ignition (Lightspeed) and guess what! sparks were visible in both (right) and (both) settings on my Spruce ignition switch.
Mark Mercier
RV-7A C-GQRV reserved
Vancouver BC
ECI O-360

Click to expand...

In one of the wiring choices------using a standard mag switch to control the Light speed------you are told to hook up a pair of wires ---I think it was 7 &9 from the output plug, to the "R" mag, and ground at the switch.

There are a couple of lugs on the switch labeled ground, check with a ohm meter to see which is always ground, use it not the one that switches the ground on and off.

As an aside, when you are phasing the coils, when you are told to "rock" the prop, you MUST do this rapidly----the magnet is passing two sensors and must do so in less than 1/2 second.

Mike

LS Readout problem

I have a LightSpeed Plasma III on my RV-10, and it has performed flawlessly for 340 hours. In the last 25 or so hours I noticed that the Digital RPM dispaly is slow to read, and it usually reads low, by as much as 300 RPM and sometimes by half. After a while it catches up and seems to read OK. Has anyone else ever seen this? By the way, I'm comparing it to the Grand rapids RPM which is picked up off of one magneto, and I checked it using a digital tach, even though at ground idle I could tell it was off. It's easy to hear the difference between 1100 and 700 RPM's.

Vic

I had the same issue.

I recently had this exact same issue. I'm sure you are not out 180 degrees but check to be sure. The spec calls for a 0.030" - 0.060" gap between the magnets and the pickup. When I checked mine they worked great but when the engine was running the engine would quit. Well, when you rotate the prop you are typically pushing on the prop. There is about 0.009" - 0.010" play in the crank and for me that was enough to pull it out of its range. When I measured with gauges I had a gap of 0.056" with the crank pushed in and 0.065" with it out. Well I brought the gap to 0.035" in and 0.045" out and it now works perfect!!!! Just tested it last night and had a big smile on my face. Now I just have to figure out why it is not generating a field voltage on my alternator and I will be ready to fly.

Another test is to turn the Lightspeed off in flight. I put 5 bucks on the fact that two EGTs will rise, and the other two will stay put. The ones that rise when you turn the EI off are the ones that are firing. The ones that don't rise aren't firing on the EI...and there's the coil to check (or both).

Trust me, rule out the simple stuff first -- the coil connections -- before you plunge into the more complex stuff like the sensor gap.

Lightspeed problem

I don't know if you have a crank sensor or a hall effect sensor. But if you have the crank sensor the space between the small pick up magnets on the and the flywheel and the sensors on the fixed plate cran sensor could be the problem. if the gap is slightly too large it is possible to get a spark when turning over the prop by hand. However when the engine starts and the flywheel moves ever so slightly forward as the prop pulls, you may be just out of range of the pickups on the crank sensor. If that is the case just shimming the crank sensor our a bit more will fix the problem.

Lightspeed, hall effect or magnets?

joehart said:

I don't know if you have a crank sensor or a hall effect sensor. But if you have the crank sensor the space between the small pick up magnets on the and the flywheel and the sensors on the fixed plate crank sensor could be the problem. if the gap is slightly too large it is possible to get a spark when turning over the prop by hand. However when the engine starts and the flywheel moves ever so slightly forward as the prop pulls, you may be just out of range of the pickups on the crank sensor. If that is the case just shimming the crank sensor our a bit more will fix the problem.

Click to expand...

I was wrestling with going with the hall effect or crank trigger. I think I made my mind up solidly for the hall effect. Since I already have two straight mag drive gears I don't need to by, it seems like a good way to go. No doubt once the flywheel magnet is set up, it works elegantly. You don't have any extra housing, bearings or engine drag. However I hear these magnet problems on occasion and think slipping a hall effect sensor in where the mag was is easier. Besides I have the mag drive hole to cover anyway. What do you all think? (although its related, sorry for hijacking the thread a little )

George, another factor between the gear driven vs direct crank pickup is the Lightspeed recommends:

"The Hall Effect sensor module should be removed every 50 hours and inspected for gear, bearing, and seal wear. After first inspection, inspect as necessary or at least every 100 hours by removing cover plate and checking for bearing and seal wear."

So, there is some history of those gear driven units needing work, whereas the direct system should not need any such service. Clearly, installation of the gear driven units is easier.

Personally, I like the no moving parts (especially no moving parts connected to my engine guts) part of the direct crank pickup system.

BTW, both systems use hall effect sensors.

Engine Woes possibly connected to Lighspeed Ignition

Gentlemen,

Anybody had this issue? Superior IO360 with one mag and one Lightspeed III with crank sensor. Performed initial set up and had to monkey with the crank sensor gap a bit due to slack in the crankshaft fore and aft, but finally got it ironed out. The engine feels and sounds great most of the time, but sometimes during cruise, I can FEEL the engine skipping slightly from time to time. Its very faint and some folks don't even feel it, but it drive me crazy.

To me,,, it feels like an ignition issue. Have any of you guys heard of a similar problem?

Chad
Glasair Super II-S FT
125 hrs.

Speeddog7 said:

Gentlemen,

Anybody had this issue? Superior IO360 with one mag and one Lightspeed III with crank sensor. Performed initial set up and had to monkey with the crank sensor gap a bit due to slack in the crankshaft fore and aft, but finally got it ironed out. The engine feels and sounds great most of the time, but sometimes during cruise, I can FEEL the engine skipping slightly from time to time. Its very faint and some folks don't even feel it, but it drive me crazy.

To me,,, it feels like an ignition issue. Have any of you guys heard of a similar problem?

Chad
Glasair Super II-S FT
125 hrs.

Click to expand...

Yes. When running LOP at fuel flows of >7.5 gph I get this. I get a very faint surge or stumble every minute or so. I remedy it by going higher or pulling power to reduce LOP fuel flow, or by running ROP. I hadn't thought about it being ignition related. I'm all ears.

Guy

How Cool?

Dan H, Dan, Vic and GMCjetpilot with replies all in the same string...

Engine Woes possibly connected to Lighspeed Ignition

Guy Prevost said:

Yes. When running LOP at fuel flows of >7.5 gph I get this. I get a very faint surge or stumble every minute or so. I remedy it by going higher or pulling power to reduce LOP fuel flow, or by running ROP. I hadn't thought about it being ignition related. I'm all ears.

Guy

Click to expand...

Guy,
Mine even does it at 8,500' rich of peak (maybe 9.5- 10gph). I'm thinking I might have a bad coil, or plug wire, or Coax. I'll run the various test that Klaus recommends for troubleshooting in his installation manual. If I find anything interesting, I'll let you know.

Chad

Speeddog7 said:

Guy,
Mine even does it at 8,500' rich of peak (maybe 9.5- 10gph). I'm thinking I might have a bad coil, or plug wire, or Coax. I'll run the various test that Klaus recommends for troubleshooting in his installation manual. If I find anything interesting, I'll let you know.

Chad

Click to expand...

As a follow up on this. I had thought my occasional LOP stumbling was fueling related. This conversation opened up the possibility in my mind that it was ignition related. I spent a day going through the troubleshooting steps in the Lightspeed manual. Everything was in spec EXCEPT: There were a couple of places where my plug wires were touching each other. There were even some wear marks on the insulation where the wires cross the boot coming from the adjacent coil. This wear occurred on the top plug wire in the photo below--right were it is resting on the boot. I will probably replace the wires at annual, but for now I carefully separated all of the Lightspeed plug wires with crossed zip ties. I have flown ~7 flights now and done my best to stress the system, severe LOP at 75% power, LOP at very low fuel flows (at altitude) etc. I have had no more issues whatsoever.

Thanks for the good ideas Chad.

Here's a photo of where most of my plug wire contact was taking place: