Troubleshooting a LSE Plasma I EI

[rvmills]

I've been going through a troubleshooting process to determine the cause and then try to fix a large RPM drop when running on only my LSE Plasma I EI (ie, when turning off the mag during run-up checks).

This thread http://www.vansairforce.com/communit...ad.php?t=44564 caught my eye, and is about a very similar drop with a Plasma III, but discusses PII vs. PIII performance, so thought I would post this separately so as not to clutter that thread. It may help others (like Bruce, the OP in that thread) with the troubleshooting process, though I will have to say, I'm not sure I've found the smoking gun yet (though it's working as of today...fingers conservatively crossed).

A little background: RV-6, IO-540, bought flying with 1 mag and 1 Plasma I. TT at purchase 455 (with a trouble-free LSE EI), TT now, 580. Last year at about 520 hrs I had a coil go bad, which manifested itself in a 200 RPM mag drop. Turned out the coil actually went "half bad", which Klaus told me could happen given the symtoms (only one spark plug in a pair not sparking). So I replaced the coil, and all was well. Klaus recommended I replace all three coils, given the age and time in service, but I opted to hold out, as I was buying avionics for a panel upgrade.

Last fall, after the panel upgrade and 5 months hangar queen time, I started experiencing a similar drop. First thought was, "well dummy, you should have listened to Klaus and should have replaced all three coils". Easy fix though, right...two more new coils, and voila...nope, ooops, same problem, and the beginning of my lessons in really troubleshooting a Plasma LSE. (And FWIW, I've found that if you do your homework and the recommended troubleshooting, Klaus is great to work with and very helpful. If you call up uninformed & looking to be schooled, he's a bit more...well, direct...AMHIK ).

So after replacing the coils, I then replaced the old hi-tension spark plug leads with new leads...no change. Replaced all the spark plugs with iridium plugs...no change. Tested the the old RG-58 cables from the brain box to the coils (should show open when disconnected at both ends, and did). But I went ahead and replaced them with RG-400 (as recommended) with new BNC's (brain-box end) and spade fittings (coil end)...no change. Tested the resistance between the appropriate DB-25 pins and the trigger coils. All checked good for the recommended 500+/- ohms, even when wiggling the wires and the coils. Didn't change the trigger coils, as it's a prop removal with my old-style trigger coils, and they checked out OK.

Next I went out and picked up a timing light and set out to check the timing and then take EGT readings to help diagnose. Timing seemed all over the place, so I sent the box back to Klaus for a bench check. Bench check went fine, but Klaus updated some of the internal components for me while it was in, just to have the latest and greatest innards. Box back and installed, and geez, no change! Arrrg.

Went back to taking EGT readings, and during that process, the mysterious RPM drop went away. Talked to Klaus, and it was possible that a plug had become "wet" during all the run-ups and drop-checks, and then dried out during the extended EGT-reading run. Checked the plugs, all good. Did some test flying, with consistently good run-up mag checks before and after flying.

Lasted that way till last week (about 60 hours of flying), and the bad drop came back, but on an intermittant basis (my favorite kind of glitch). It would drop sometimes, and then "right" itself during the run-up. Sometimes back and forth. So no flying, and back to the troubleshooting routine. Swapped coils, swapped wires, swapped plugs...still intermittent, and still in the same pair of cylinders (3/4). Thought it might be heat (seemed better when hot), thought it might be RPM (seemed better when higher), but no rhyme or reason appeared, and those ideas failed to be repeatable.

Re-checked the firing coil wires and the trigger coil wires, all checked good, and then cleaned and re-set all the connections, but no change. Even re-secured the spark plug wires, making sure they weren't laying on each other anywhere along the runs. Basically, I've changed everything in the system except the trigger coils and the brain box. To change both is about an $1100 fix (to upgrade to a II or III box and the new-style crank sensor). Not much different than a new pair of mags and harnesses...hmmm.

One of the things I noted in the troubleshooting guide was to ensure that the three low voltage trigger coil wires were routed away from all high voltage wires. Mine were bundled with the EGT and CHT probe wires (also low-v), as well as the wires to the alternator. So I separated them, and wrapped the coil wires separately, tidied up all the wire bundles and made sure all the connections were clean and solid (again). Expected it to remain the same, and figured if it did, I'd send the box back, and if it checked good again, it's off with the prop and replace the trigger coils.

Then, as I re-mounted the box under the panel today, I noticed some drops of hydraulic fluid on a nearby fitting. Just before this LSE issue (re)started, I replaced the brake fittings on the cylinders, and had one line pop out of it's fitting on test. Thought I had cleaned up all the mess, but obviously missed the spots that required getting upside down under the panel to see. Just above where I saw the drops was the brain box, and with the BNC's off, I could see a small ring of hydraulic fluid around the base of the male BNC of, you guessed it, the connector for the channel to #3/4 cylinders. The inside of both connectors looked good, but I cleaned them carefully and blew them out with air, just in case, and reconnected all.

Still not too hopeful, and ready to pack up the box, I went out and ran it up. No drop...nada...standard LSE-only purrr with the mag off. Ran it for a while, cycling through the EGTs on my VM-1000 and taking several readings, while checking several times for a drop that never happened. Couldn't make it happen if I tried.

Pylon Racing School here at Stead, and then wx prevented me from local test-flying, but that is to follow, before I claim victory. Could be the hyd fluid. Could be the wire reroute. Could be the take it all apart and put it back together carefully factor, or a combination of the above; Could also be a gremlin just waiting to come back (not so naive as to ignore that!) but I'll be watching it closely, as I don't like "too good to be true" fixes, and really dislike intermittent and "could not duplicate" gripes.

Will post if it comes back and I either find a fix or get a new box or a pair of mags, but if this helps someone troubleshoot an LSE issue, all the better. Klaus' TS guide on his site is pretty good, and he spent some good time on the phone with me as I ran through it. Bruce (from that other thread), I hope your #3/4 drop is just a coil, but if not, maybe some of the above troubleshooting steps may help you find the bogey!

Oh yeah, and if you blow a brake line, look for that nasty stuff everywhere!

Cheers,
Bob

[rvmills]

Well, as it turned out, the gremlin came back quickly, and remains intermittent.

So the prop came off today to inspect the trigger coils, and though they seem to be working, they show that the studs that are attached to the timing wheel and pass by the coils have come in slight contact with the coils (grazing marks), so replacements are on the way. They're the last components that I can replace, other than the brain box itself, for which there are no replacements (unless I upgrade to a II or III, which requires a change to the new-style crank sensor).

While the prop is off, the box is going in for another bench check, so I can rule out all bogeys. When all parts are back, this last section of the system will get a careful install (solid clean connections, a solid mounting of the trigger coil bracket, and all trigger coil gaps checked and set to spec. Checking those gaps had shown too close on one coil, and too wide on another (by .002 or so, whch Klaus says should not cause the issues at hand), while the third was unreachable when installed. That third coil showed the most grazing, but its channel had been trouble free, as had the coil with too small a gap.

So if this round of repairs doesn't fix it, it's decision time (II, III or mags).

If anyone has any thoughts or ideas, I'm all ears...and though there may not be many Plasma I systems out there, hope this will be a ref for others if the need arises.

Cheers,
Bob

[Geico266]

I vote for Dual Slick Mags.

With an IO-540, you certainly have enough power if you get a reliable spark to the cylinders. What are you trying to gain? How much of your time have you spent grounded and working on a faulty ignition system? Replace it and get back in the air!

Have you taken a look at the wire coming off position sensor? It's building plenum (speaker) wire, certainly not fit for an engine compartment. Take a look at that wire I took off my IO-540 after I ran an EGT balancing (high temps for 5 mins) test.

http://geicodevelopment.com/light_speed_engineering

JMHO

[bcondrey]

Larry,

You make comments about this a lot - in the interest of full disclosure you might also mention that yours was a victim of improper installation (wire routing). I'm running dual LSEs, have the wiring properly routed, have run the same EGT test and haven't had any issues at all.

Bob
RV-10 N442PM

[rvmills]

Originally Posted by Geico266

I vote for Dual Slick Mags.

With an IO-540, you certainly have enough power if you get a reliable spark to the cylinders. What are you trying to gain? How much of your time have you spent grounded and working on a faulty ignition system? Replace it and get back in the air!

Have you taken a look at the wire coming off position sensor? It's building plenum (speaker) wire, certainly not fit for an engine compartment. Take a look at that wire I took off my IO-540 after I ran an EGT balancing (high temps for 5 mins) test.

http://geicodevelopment.com/light_speed_engineering

JMHO

Larry,

Not sure if you had the newer crank sensor plate in your previous LSE install, but I have the pre-2001 trigger coil set-up. The wires I have running from the DB-25 connector on the brain box to the three trigger coils that are mounted to a bracket on the front of the crankcase (and just behind the timing wheel) are quite different than the wire in your picture. They are shielded wire with a silver (almost white) shield/jacket. They are the ones I just separated from the rest of the wires running past the engine (EGT/CHT/Alternator) and then spiral-wrapped separately. However, they are in great shape, no signs of heat damage, and they checked OK for correct resistance.

That wire in your picture truly did look aweful, and I've taken a close look at all my wires for similar damage (and will again!).

With regards to time spent, and what I'm trying to gain (and your comments do not fall on deaf ears)...

The system was installed and working really well when I bought the airplane. The first coil replacement took me just a little time to troubleshoot and replace, but not that bad. However, when this intermittent problem cropped up, it has kept me down (and busy) far more than I'd like (about a week the first time it popped up), and now it'll be a couple weeks for this round of troubleshooting. Quite frustrating.

On the issue of what's to gain, it's really a matter of trying to re-gain what I had, which is a nice running engine and a very smooth EI (and when it works, it really works great...but that when is becoming "the rub"). I've invested a lot of sweat equity, but not nearly the cost of a pair of mags or a new EI. I'm dealing with a bit of a legacy system, but I figure I'll give it my best shot. Replacing the trigger coils is likely the last in my Quihotiesque dashes at this windmill. I haven't given up yet, as there are a lot of aircraft running similar EIs with great success, and this aircraft was one of them till now.

If I'm successful in bringing the system back to it's original great performance for a fraction of the cost of new mags or a new EI, and feel I can trust it, then I'll call it perseverence and a bit of a victory. If it doesn't work out, I've chased a worm down a hole a bit, but have learned a lot. So then it'll be decision time between an upgrade to a II or III, or a pair of mags.

Either of those options, of course, have pros and cons. Rather than kick off the EI/mag debate (for which I can offer arguments on both sides), I'll just cross that bridge if I get to it. But believe me, it's been on my mind, and a topic of discussion with my airport buds.

Cheers,
Bob

[master pilot]

I am also chasing an intermittent misfiring # 3 cylinder. Klaus now thinks I should replace the RG58 wiring between the brain, on the firewall, and the two coils with newer more temp stable wire. Tis is a 2002 installation and better wiring is now available. Hope this helps as it is very frustrating.

[Geico266]

Originally Posted by bcondrey

Larry,

You make comments about this a lot - in the interest of full disclosure you might also mention that yours was a victim of improper installation (wire routing). I'm running dual LSEs, have the wiring properly routed, have run the same EGT test and haven't had any issues at all.

Bob
RV-10 N442PM

You are correct Bob, the installation of the wires near the alternator wires was incorrect (I bought the plane flying), but I was not referring to the LSE Plasma II box failing and bringing me out of the air, I was referring to the use of wire that is not rated for aircraft. No matter how it is installed, IMHO, it should not be used in any firewall forward application. It is "plenum wire", building speaker wire, and I believe it contributed to my "situation". I bring this up from time to time so that builders are aware of the problem and can choose to use the LSE supplied wire or substitute the correct wire for this firewall forward application. I hope you can see the difference in my comments.

The box that failed on my plane seemed to be due to overheating which is a common problem on the older units, and it was addressed by LSE adding a cooling port (at my expense). The plane ran fine in cool weather, but failed during hot weather when the plane sat outside in the sun.

I'm glad you are having good results with your application, I was not so fortunate and made the switch back to dual Slicks Mags, not so much as a hickup so far.

[rvmills]

Originally Posted by master pilot

I am also chasing an intermittent misfiring # 3 cylinder. Klaus now thinks I should replace the RG58 wiring between the brain, on the firewall, and the two coils with newer more temp stable wire. Tis is a 2002 installation and better wiring is now available. Hope this helps as it is very frustrating.

MP,

I changed out the original RG-58 cables to RG-400 when the problem first showed up. No change unfortunately.

I'm interested in the indications you are seeing when your cylinder is misfiring. When the system is misbehavin', my #3 and (especially) #4 indicate about 150 or more degrees lower than the other 4 cylinders. Then when I turn off the mag (and get the large RPM drop), the #3 and 4 EGTs rise quickly by 100-200 degrees, while the other 4 show a slow, modest rise (maybe 20 degrees).

If the coil were bad, or that LSE channel had just plain failed, the EGT on #3 and 4 would drop when the mag is turned off (since no spark at all would then be going to those cylinders).

Seems like a spark timing issue, so I checked the timing, and found this:

Cyl / Timing (MP line on) / Timing (MP line off)
1/2 / 37 / 25
3/4 / 35 / 35
5/6 / 37 / 25

The middle channel appears as though is not advancing when the MP line is removed, so it seems like it could be a box issue (and another reason I sent it in). Can't say for sure, but since up to the point where I re-checked that timing, I had not ever touched the timing coils or the timing studs, it would seem to be external to that part of the system. However, I am now changing the coils, to rule them out (or confirm them...or the gaps) as the culprit.

Any chance you have taken EGT readings or checked the timing (to compare results with mine)? Also, are you running a Plasma I, and what type of crank sensor do you have.

Thanks for chiming in...appreaciate the heads-up!

Cheers,
Bob

[Mike S]

Originally Posted by rvmills

Seems like a spark timing issue, so I checked the timing, and found this:

Cyl / Timing (MP line on) / Timing (MP line off)
1/2 / 37 / 25
3/4 / 35 / 35
5/6 / 37 / 25

The middle channel appears as though is not advancing when the MP line is removed, so it seems like it could be a box issue


Bob

Agree, only other reason I can think of is the pickup sensor for cyl 3/4 ---- and only if there are two sensors at each location. I.E., a pickup for standard timing, and one for advance.

Just speculating here, I have no empirical knowledge of these units.

Good Luck.

[rvmills]

Originally Posted by Mike S

Agree, only other reason I can think of is the pickup sensor for cyl 3/4 ---- and only if there are two sensors at each location. I.E., a pickup for standard timing, and one for advance.

Just speculating here, I have no empirical knowledge of these units.

Good Luck.

Mike,

For the Plasma I with the pre-2001 trigger coil arrangement, there's one trigger coil for each channel, located 120 deg apart on a bracket behind the timing wheel. The timing wheel has two studs protruding down from it, placed at TDC (for starting) and 37 degrees BTDC for running (actually the second one can be placed in various positions, depending on the compression ratio of the pistons).

Klaus had me check to see if the coil was firing by checking to see if I had spark when passing a screwdriver quickly by the coil to see if the magnet moved and generated a spark. It did with the screwdriver test, and also by passing the stud over the coil by moving the prop back and forth quickly (plugs out, of course).

So, though my trigger coil to stud gaps are off slightly (well were...its all apart now) it still was sparking as it should have been. Of course, when the engine is running, there may have been some flex or precession that caused the gap to change or the trigger coil to malfunction. So new coils and a fresh mount, and we'll see how the timing and engine runs go.

Thanks for the good wishes!

Cheers,
Bob