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Light Speed Ignition running rough

Stroh21

Well Known Member
Hello VAF!

During my engine run-up this past weekend, I discovered the Light Speed side (Left) of engine was running rough. I noticed a corresponding #1 and #2 cylinder temps started to drop while I was on the left side. I couldn't leave it there long because the RPM was decaying pretty rapidly. On the Right Side, the engine was running smooth and normal. The engine time was just over 1000 hours and I was planning on replacing the plugs anyway, so I went ahead and changed all of the left side plugs. When I ran it tonight to see if it fixed the problem, the engine was actually running worse than before on the left side and still running smooth on the right side. I also noticed the engine ran slightly rough while in both. I'm wondering if I have a timing problem with my light speed ignition? If so, what tools and other parts will I need to trouble shoot? Is there previously posted trouble shooting advice?

The plane was running fine two weeks ago.

Thank you for your help!

Matt
 
Coil?

1 and 2 share a coil. I'd look at that. See if it has a loose wire running to it. Check the coil for resistance. Info on troubleshooting on Lightspeed's website.

Ed Holyoke
 
I echo what Bob says, sounds exactly like bad coil symptoms I have had in the past. It’s a connection or more likely the coil itself.
G
 
Pull the female spade connectors on the coils. Look for evidence of fretting and burning.
 
Coax Connection

I’m with Dan in this one. I’d carefully check the crimp to the shield portion of the coaxial cable into the coil. I really disliked the way this was supposed to be done, gathering the shield into a twisted bundle, then crimping it. Instead I did a clean strip of the insulation, installed a solder sleeve, and ran a short pigtail out and put the spade connector on that crimp. 100 hours later, no issues. I check them during annual condition inspection.
 
Matt,

As others have posted, Lightspeed coils tend to be fragile. The following are causes of coils going bad:
- High resistance plugs. Check them or just replace - but check before installing.
- High resistance plug wires. I suspect this is the reason why Klaus says to replace them periodically.
- Any marginal connection (coil, wire, plug, etc.)
- Some fail just “because”.

As this happened on the plugs on one coil, I’d guess the box is still good. BUT do not overlook a box issue until you rule it out by replacing the coil. I’ve seen a few boxes just go south for no reason.

Carl
 
A friend had the same symptoms on his RV-7 with dual LS Plasma II. Replaced a coil on the affected cylinders, which didn't help. Called Klaus and he said it is likely a problem with the connector in the hall effect unit that is installed in place of a magneto. Cleaned the connector and it was fine for a few flights before doing it again. Klaus also said they were known to have issues internally on the DB-9 connector and could fix it for $150 (each) plus shipping.

Now running P-Mags and very happy.
 
A friend had the same symptoms on his RV-7 with dual LS Plasma II. Replaced a coil on the affected cylinders, which didn't help. Called Klaus and he said it is likely a problem with the connector in the hall effect unit that is installed in place of a magneto. Cleaned the connector and it was fine for a few flights before doing it again. Klaus also said they were known to have issues internally on the DB-9 connector and could fix it for $150 (each) plus shipping.

The message above well describes an issue that I had a year or so ago. When on the electronic ignition, the engine ran awful, and at times, barely ran. After some head scratching, it was the DB-9 connector that had the problem.
 
The message above well describes an issue that I had a year or so ago. When on the electronic ignition, the engine ran awful, and at times, barely ran. After some head scratching, it was the DB-9 connector that had the problem.

Boy, this certainly doesn’t give me a warm fuzzy feeling. I have dual light speeds and so far it seems to be working OK
 
I have found the lightspeeds to be reliable, but as with any system on our aircraft, they need inspection and TLC at regular intervals.

Dan mentioned the wires. I've always replaced those at 5 yrs as spec'd. The coils should be checked for proper resistance, at least once per year. They should normally be around 8.1K to 9.3 K ohms. They tend to get higher than that before they hard fail, so if you are checking them regularly you shouldn't have a hard coil fail.

It's in my book. :)

Vic
 
I bought a bunch of extension screws with knurled knobs (https://www.amazon.com/10-PACK-Screws-Parallel-Serial-Connectors/dp/B016S7OBOE) so I could tighten and verify tightness by touch. I replace them on every connector that relies on those to secure the connection. Inspired by one of the connectors on my dual lightspeed setup getting loose but it was incredibly difficult to get a screwdriver in where it was mounted (20/20 hindsight about mounting location fixed when panel was upgraded). That and one spade connector failed (my fault) on one of the coils which produced the symptoms described by the OP and was easily fixed once spotted. The control boxes seem bulletproof but I worry how long the system will be available. I'm discovering that these kind of systems don't have the lifespan I'd want to count on.
 
The control boxes seem bulletproof but I worry how long the system will be available. I'm discovering that these kind of systems don't have the lifespan I'd want to count on.

I've had Klaus' Plasma II system on one of my planes (same box) for 31 years.
 
Thank you to everyone for the replies. The support here is what makes this community great! I began tracing wires and found one that had become disconnected in the forward baggage compartment. In the end, totally my fault and felt pretty silly after finding it. Fortunately, now I have new spark plugs on top and everything else is running great again! Also learned a lot, which is also a bonus! “Thank you“ to everyone again.
 
I have found the lightspeeds to be reliable, but as with any system on our aircraft, they need inspection and TLC at regular intervals.

Dan mentioned the wires. I've always replaced those at 5 yrs as spec'd. The coils should be checked for proper resistance, at least once per year. They should normally be around 8.1K to 9.3 K ohms. They tend to get higher than that before they hard fail, so if you are checking them regularly you shouldn't have a hard coil fail.

It's in my book. :)

Vic
 
My Lightspeed data point

I hope I don't jinx myself. Here's another positive data point for Lightspeed. I've been running one crank triggered Lightspeed Plasma II and one Slick 4371 for 12 years and almost 900 hours. For comparison, I've complied with one Slick AD and 1 or 2 Slick service bulletins during that time. I rebuilt (IRAN) the Slick myself about 9 months ago.

The Lightspeed has been rock solid to this point. It is installed with the brain box not on the firewall but under the panel on a rib to help with cooling. Extra care for the trigger wire routing and extra support at the coil connectors was taken. No parts or wires have ever been replaced, other than spark plugs. I did purchase a spare coil recently just in case. My biggest concern would be a manifold pressure sensor failure which I understand can advance the timing too far in flight.

I believe any of these systems can have issues. If it has moving parts it will have wear at some point. I've had some recent experience helping a friend with P mags and they certainly have their own idiosyncrasies to watch for. Although I'm watching the Sure-Fly with interest for a possible future Slick replacement it would require electrical system surgery to add another battery or alternator for redundancy and I'm not ready to go there on a VFR airplane. I like simple and light. :)
 
Thank you to everyone for the replies. The support here is what makes this community great! I began tracing wires and found one that had become disconnected in the forward baggage compartment. In the end, totally my fault and felt pretty silly after finding it. Fortunately, now I have new spark plugs on top and everything else is running great again! Also learned a lot, which is also a bonus! “Thank you“ to everyone again.

Matt,

Glad you found the problem. Out of curiosity, what wire was disconnected?
 
I've had lightspeed on my IO-540 for 14 years, and on my IO-390 for 4 now. I wouldn't be without it. I do tend to agree with the comments about not knowing how long vendors will be around, so I solved that problem for myself by buying a spare control box for both planes. They're light enough that I even carry it along on my RV-10. But, with that, I have no worry about if the vendor disappears. I can run it for as many years as I want. I keep spare coils, plug wire, and plugs around and carry a spare coil as well. I hope to be running them at 31 years like another posted mentioned.

I will also add this: If you're running a hall effect sensor or the old "around the crank" sensor, they do have a better sensor now called the "mini sensor" that might be worth the hassle. When I recently swapped engines on the RV-10, I switched to the mini sensor. I believe those will be more durable long term, although I had no issues with mine and it was an old generation pickup around the crank.

One last tip. If you do switch to the mini sensor, there is a bracket that you need to mount it with. I did not use that bracket on my RV-10 install, but a friend created a much easier an less intrusive bracket. If someone is ever interested in that, I could share the design so you could have it CNC machined. It's super durable and solid. I have pics but haven't done a write-up yet on the swap so nothing I can link to today.
 
I guess I should mention the Lightspeed's I've installed on 5 homebuilts with an aggregate 7,000+ hours are all direct crank trigger. I would not fly with one of the Hall effect (mag hole) modules and agree the new mini-senosr is an improvement of over the large diameter variants Klaus has produced over the years - but all direct crank have been trouble free if care is taken on routing the wires.

I've had one coil soft failure, and carry a spare.
 
I guess I should mention the Lightspeed's I've installed on 5 homebuilts with an aggregate 7,000+ hours are all direct crank trigger. I would not fly with one of the Hall effect (mag hole) modules and agree the new mini-senosr is an improvement of over the large diameter variants Klaus has produced over the years - but all direct crank have been trouble free if care is taken on routing the wires.

I've had one coil soft failure, and carry a spare.

I have dual lightspeed with dual hall effect mag hole modules. 600 hours and all is well
 
It was one of the twist-off coax cable on the box mounted in my forward baggage compartment. It must have gotten knocked loose while loading gear.

I have a Lightspeed box mounted there as well; been thinking about adding a shield to prevent contact with baggage...
 
recently went dual lightspeed, runs smoother and picked up both speed and fuel economy. made a shelf to be able to still use the fwd baggage.
 

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