Sometimes bad isn't bad - (ETA) Corvair EP/EPX Distributor Service

General
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Friends,

It was a beautiful morning with temps in the upper 60’s. With afternoon temps forecast for the upper 90’s I decided to go early and enjoy the relatively cool summer air that would be smooth before the heat of the day set in.

I was alone at the airport, which is quite usual during the week, as I pulled Myunn out for a short 40 mile jaunt over for some of that 100LL she likes now and again. Runup complete we blasted off into the extremely smooth and clear morning air. It had been a few days since I let Jeeves the A/P fly the plane, so I programmed in my destination and in my best Jean-Luc Picard voice I said “engage” as I pressed the servo button into action.

Nice flight and the fuel there is about the cheapest in the local area. I walked around the vacant offices, went to the restroom, and returned to the plane to get high again. Once more a successful runup and away we went! Turning left at about 700’ I touched the trim and decided that I would hand fly the plane back to the station.

Just then the power went away. No warning the engine just quit making power. I pushed the nose over and looked out of the canopy, quite surprised at how calm I felt as I said to my self, “it’s about to get real.” Quickly I reached over to flip on the back up ignition (Corvairs have dual ignition but generally only one is used at a time).

As I looked over to confirm the switch I noticed the prop still turning. The engine was as smooth as silk but seemed to be at idle power yet all the controls (throttle, mixture, & carb heat) were against the firewall. As quickly as I flipped on the backup ignition it came roaring back to full power with all temps and pressures normal.

I turned back and did a precautionary landing. A full runup again found no indications of a concern so being alone (I would have not taken a passenger in this scenario) I decided to use the backup ignition to launch with and then see if the Primary would work. At just above 2K feet I went from backup to primary and flew all the way back to home base without a hiccup.

I had a very brief indication a few flights ago that hinted that something might be amiss but it was so brief I wondered if I really felt it or maybe it was just the bumpy air.

I tore into it today and have a belief that the electronic ignition module is failing or the coil for that side is bad. So for about $300.00 I have ordered replacement trigger parts and coils for both ignition systems. Small money for piece of mind.

It’s been absolutely rock solid for nearly 400 hours but it seems my plane was whispering that she wanted some new parts and I didn’t hear her until she shouted at me.

Dale
3.0 Corvair/Taildragger

PS: A very special shout out to Dan Weseman of Sport Performance Aviation. He answered my email quickly and gave me some very sound instructions. Thanks Dan!

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How do Sonex aircraft handle mid day /thermic rough air?
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That’s a scary title for a happy ending!

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Wow! very glad nothing more serious happened! this kind of thing worries me to some extent, so I attempt to make everything verrified functional on each flight , just as you did. But, when it does ‘shout’ at you, its best to listen! Good job!!

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Glad to hear you and your Sonex are safe. Thanks for reporting. Not sure I would have stayed so :call_me_hand:

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Point taken .. I did an edit on the title.

Dale

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how about “All’s well that ends well”?
glad to see you.

I’ll make a note for inclusion in my maintenance manual.

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Hey John,

Inspection found that the main ignition coil was leaking (epoxy filled). Something I couldn’t see on preflight. They’ve been on there for nearly 400 hours and 14 years of flying. If AI is accurate the Bosch Blue 00012 coils that I use are “generally speaking” good for about 10 years. Of course that is very subjective to heat and operation cycles. So I think it wise to change out all the ignition parts (XRi trigger, points & condenser, and both coils) at 10 years or less. From the symptoms that occurred I believe the XRi unit is what failed. I haven’t ohm tested the coils yet to see if they are good but either way they are headed to the round file. Not sure how to test the XRi unit but it’s history also.

FWIW … I checked the points and timing at annual and all was well. No way to really test the XRi unit except the full advance timing test with a light.

As I noted above in another post the parts to replace both ignition triggers and coils was 300 bucks. Not much at all in aviation money.

I’m a bit humbled that I didn’t catch this earlier. So that’s the main reason for posting i.e. sometimes when things are going well we get comfortable and let our due diligence slip a little. I thank the Good Lord for helping me catch this before it got ugly.

Dale
3.0 Corvair/Taildragger

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Dale, thanks so much for sharing. Glad to hear you and the plane are alright! Props to you for handling the situation in a calm and professional manner.

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Friends,

I took the liberty of editing the title (again) as I wanted to share more information but didn’t think it necessary to start another thread.

The subject is the distributor used on a William Wynne Corvair conversion. These are known as EP (Electronic -points) units with the X denoting that a weather pack connector was added to aid in removal. The Flycorvair site shows “3300s Distributor service” and it is highly recommended that builders use this service as William has all the parts to repair and tools to test the distributor before it is returned to you. He knows what he’s looking at as he is the designer of this system. Use him if you can.

Having said that, I sent an inquiry about having mine done but it’s Airventure time and not receiving a response wasn’t a surprise. The man is quite busy and I get that.

Being a fair mechanic I felt confident that I could do what needed to be done although I didn’t possess a tool I’d like to have had i.e. a dwell meter. I felt that in order to do this properly the distributor need to be removed (although points. condenser, cap, & rotor are easily done without pulling the unit) so inspection of the drive gear, shaft end play & wobble can be ascertained. I also inspected the mechanical advance weights, springs, and distributor cam lobes.

Once the unit is out, removing the points plate to install a new FAST (Fuel & Spark Technology) XRi module is pretty straight forward. Likewise also the points for the back-up ignition.

Before making any decision to do this you must know how to static time an engine and it is REQUIRED to use a timing light to set the final ignition advance. Mine was set to 28º BTDC and is done so behind a spinning prop. This isn’t something for the faint of heart. If you fly a Corvair, verifying advance timing with a timing light must be performed every year as part of the condition inspection. Not to preach - but don’t skip this part!

There is a whole lot more to doing this than I’ve described in this brief post. I have no idea how many may be running these units but I post this to say that if I can assist anyone in doing this correctly, feel free to send a DM.

Myunn is back together and all testing and settings are as they should be. Waiting on a break in the heat and some calmer air to go for a ride.

Best,

Dale
3.0 Corvair/Taildragger

PS: A photo of the EP plate ready to be reinstalled:

image
image810×1080 127 KB

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Breaker points! That brings me back. We also check the timing behind a spinning prop, but have to adjust with the engine stopped.

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Yep … contact breaker points! I use and recommend Echlin cause they are the best. I was very thankful for those points when the electronic had a hiccup. In service they last a very long time as they are used for starting and back-up and get very little wear. The main ignition is the XRi unit and it needs no adjustment. This one lasted 14 years and I should have changed it sooner.

The ignition advance is mechanical and works much like in the auto although it is recurved to have all the ignition advance in by 2600 or greater. The full advance is observed with a timing light and set at 28º BTDC with the engine at full static RPM and that requires working behind the prop. The good news is the distributor is in the rear, near the firewall, so there is a couple of feet for safety. When making any adjustments I shut the engine down. It was very helpful to have a competent operator in the plane that was locked, chocked, blocked, and bound to the ground!

Flycorvair has designed a new distributor that has two electronic units and no mechanical advance. Much easier to set after install. Great looking units and futuristic. Current (pun not intended) price complete is $1199.00.

DFI Distributor

Dale
3.0 Corvair/Taildragger

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Hi Dale,
In one of the first videos , the new owner stephen indicated hes open to helping people with other engine choices. Maybe their mount vendor could get a mount for corvair for the b models.
WW and spa have fwf for legacy sonex , but i read they werent interested in develop for b model sonex due to limited return.
Glad you got the plane down safely!

best,
michael.

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Hi Michael,

Having a B-model/Highwing Corvair mount would be encouraging. The other encouragement would be some winning lottery numbers …

Good to see Sonex up and running again!

Dale
3.0 Corvair/Taildragger

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Friends,

Excuse me for taking the liberty of quoting myself … “Being a fair mechanic I felt confident that I could do what needed to be done although I didn’t possess a tool I’d like to have had i.e. a dwell meter.”

Well … @Bryan_Cotton says this hobby is all about buying tools so I took his advice and found an older analog dwell meter to add to the tool collection. Now to be sure I’m confident in my ability to set a new set of points with a feeler gauge but there’s a lot of good information to be had from reading dwell. Some of these will also apply to electronic ignitions especially when looking at coil saturation time and/or variations in the system (wobble) that could cause erratic coil charging and weak ignition issues (items # 4 & 6):

With assistance from my AI secretary here is a list for your consideration.

  1. Point gap accuracy & stability — Shows if the gap is set correctly and whether it drifts due to wear/lubrication issues.

  2. Distributor cam condition — Uneven dwell indicates worn or inconsistent cam lobes.

  3. High‑RPM point behavior — Unstable dwell exposes point bounce or float.

  4. Coil charging & spark strength — Dwell directly reflects coil saturation; too much or too little affects spark energy and coil temperature.

  5. Condenser health — A weak condenser causes dwell to wander with RPM or temperature.

  6. System shaft & bushing wear — Variations show radial/axial play or heat‑related movement.

  7. Advance mechanism function — Dwell changes under mechanical advance indicate binding or plate movement issues.

  8. Point contact surface condition — Jumping dwell at steady RPM points to pitted, burned, or misaligned points.

  9. Grounding & electrical noise — Erratic dwell can signal poor distributor grounding or electrical interference.

  10. Overall ignition system health — Stable dwell across RPM and temperature means the entire mechanical ignition system is behaving properly.

FWIW …

Dale
3.0 Corvair/Taildragger

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I still have my old dwell meter from the 80s!

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I’m curious, have you have run this by WW to get his input?

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HI Kevin,

Not sure what question you are asking. I sent a request but got no response as he’s no doubt tied up with getting to Airventure. It’s a simple dual ignition system that is easy enough to repair and parts are readily available . I’m very well versed in setting static timing, point gap, and full advance timing with a light. I did get some valuable input from Dan Weseman.

What I didn’t have was a dwell meter. I can set point gap with a gauge but WW does say that the gap should be set by dwell. I wanted the meter as they are very good for diagnosing other issues also. I found no concerns at all with the distributor. Secondary timing was set behind the primary (as it should be) and full advance was set to 28º BTDC as he shows in the manual (I have four) and in his online YouTube videos.

Testing has shown both systems to be functioning exactly as designed after replacing the triggers and coils.

If your question has to do with perhaps how the part failed … not sure he could help as I have not found anyway to test the module itself. Both coils and the condenser tested good although as I mentioned earlier, one coil was leaking a bit. Of course all of those parts were replaced also.

Dale
3.0 Corvair/Taildragger

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The new distributor is well worth the price of admission.

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Do you have one of these? I’m seriously asking because I’d like to get more info on how they are performing in the field. The price doesn’t scare me as really good aviation stuff is worth the cost. I also like the cap/rotor set up much better.

Having said that … these are not currently available per the FlyCorvair website. I’d also add that the older E/P distributors have a few advantages (at least for me):

  1. I like points. They are “old school” but they work and generally will give some indication when they are misadjusted or failing from old age. Easy to replace.

  2. Replacement parts for the older E/P distributors are available and the cost is reasonable. The best points (Echlin from NAPA) are about twenty five bucks. XRi modules are generally less than a hundred.

  3. The E/P distributor uses a mechanical advance that makes for easy starting and very smooth throttle changes. The MA-3SPA carb (with accelerator pump) helps.

  4. These are well proven and I don’t know of any system failures by using this setup (yes my primary had a hiccup but the back up did its thing so the system worked).

No doubt if I fly this Cleanex long enough I’ll change out to the newer DFI distributor as the one unpleasant part of the E/P distributor is setting full advance behind a prop spinning at 2700 RPM. Other than that … :shushing_face:

Dale
3.0 Corvair/Taildragger

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