What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

My O-320 Won't Start

Towline

Member
Hi folks - first time posting here as I've got a bit of an intermittent problem.

Purchased a 2002 finished RV-6 back in Feb 2018.

  • O-320 D1A
  • LSE Plasma 1 unit on the right (top plugs)
  • Slick Mag with impulse on left (bottom plugs)
  • ACS starter switch

From when we bought the aircraft until about a month ago, the engine would fire within 2 turns of the prop - fantastic. Now up until the time it started misbehaving here in the UK we had crazy hot and dry weather for about 8-10 weeks - so initially we though atmospherics were to blame.

Around the time that the temp dropped back to normal UK summer levels, we noticed the engine becoming harder to start, as well as the odd backfire (afterfire) when doing mag checks at high RPM when turning the Plasma off and checking RPM on magneto only (the LEFT key position).

We're now at the point where the engine can be very hard to start, often kicks back after letting go of the starter and when it finally does start, seems to do so after you've let go of the starter switch and gone to BOTH with the key. There is no sign of combustion most of the time, no popping from exhausts.

When the engine is running, it performs fine and the 'mag' check on both sides is normal.

Things we've checked so far with assistance from an LAA Inspector
  1. Impulse coupling clicks as it should when turning the prop.
  2. Magneto is firing the bottom spark plugs - visual check of each plug when cranking, (so surely the key switch must be fine?).
  3. Fuel is getting into the carb (M4-SPA) from the electric pump and throttle accelerator pump.
  4. Cranking engine with the Plasma unit circuit breaker pulled = no start but no kickback.
  5. Cracking with Plasma live = kicks back 50% of the time.
  6. Installed bigger battery = no improvement.
  7. Injected fuel direct into cylinders with a syringe = no noticeable combustion.

Our next line of enquiry is the carb idle adjust, because the bottom plugs should be igniting the fuel and air. If this proves fruitless we will probably investigate the key switch and maybe contact Klaus about the Plasma - he might know more.

I'd be greatful for anybody who has experience a similar situation. I have seen one other thread about an RV that started after you release the switch, but that was dual mags and obviously switch related.
 
Last edited:
Are you able to start the engine on the mag only? I would try a bit harder to see if you can make it work. This will help in isolating problem areas. Don't forget, every significant drop in temp requires incrementally more primer shot in order to kick over.

The fact that you are getting kickbacks while starting on only the LS, would seem to indicate a problem with it's timing. I have no experience with those ignitions, but several threads here full of info on common failure points. I would definately get a timing gun on the engine to see if the base line timing is correct, as well as checking for blockage in the vacuum line to the control box.

Regular kickbacks during start operations are typically due to an ignition timing that is too advanced.

While it could be other things, the best place to start on addressing your hard start issues would be ignition, given that you are having problems with your LS ign. Mostly likely issues are some failure in the CPU or some issue with the wiring to the crank sensor or the sensor itself.

Larry
 
Last edited:
Our next line of enquiry is the carb idle adjust, because the bottom plugs should be igniting the fuel and air. If this proves fruitless we will probably investigate the key switch and maybe contact Klaus about the Plasma - he might know more.

I'd be greatful for anybody who has experience a similar situation. I have seen one other thread about an RV that started after you release the switch, but that was dual mags and obviously switch related.

If your idle mixture is adequate to run your engine at 700 RPM without roughness, it is good enough to kick over. Initial starting is all about the amount of prime shot you use. Whether it runs after catching is all about the idle mixture.

Larry
 
It's a long shot, but...........

Sometimes after extreme weather conditions, especially high humidity, the mag points can become corroded. Try cleaning the mag points by running a business card through the contacts several times.
 
Last edited:
Sometimes after extreme weather conditions, especially high humidity, the mag points can become corroded. Try cleaning the mag points by running a business card through the contacts several times.

Wow, I haven't heard that one in a long time! Thanks, Mel, for refreshing my memory of some great "field fixes" shared with me by wise old mechanics years ago. I had completely forgotten about the "business card points file". You've put a big grin on my face with that memory!
 
Disconnect the p-lead from the mag, and try to start it on the mag only. That way you can 100% eliminate the switch.
 
Disconnect the p-lead from the mag, and try to start it on the mag only. That way you can 100% eliminate the switch.

^^^^ This^^^^ Does the LSE have the crank/flywheel trigger, or the mag hole Hall effect module?
 
Disconnect the p-lead from the mag, and try to start it on the mag only. That way you can 100% eliminate the switch.

Yes, too many variables. :)

Disregard the LSE and just use the left impulse mag. like most other certified planes on your field.

Is the mag. timed correctly? Let the impulse coupler click and then go back 30 degrees on the prop and come up to the correct timing point, probably 25 degrees. Magneto timing was not mentioned in the OP.

Could you be over-priming? Perhaps a bad magneto?
 
Wow, I haven't heard that one in a long time! Thanks, Mel, for refreshing my memory of some great "field fixes" shared with me by wise old mechanics years ago. I had completely forgotten about the "business card points file". You've put a big grin on my face with that memory!

Oops, Did I just tell my age?
 
starts when keg is at both

my plane was slowly getting harder to start and then it would start when I let go of the key to stop cranking and then it started on both with the last turn off the prop. it was a worn impulse coupling on the left slick mag. I replaced the mag. my mag checks were good when running also
 
Last edited:
Not sure what triggers you have on the Lightspeed but a good check is to remove the plugs, lay them on the top of the engine and pass a screwdriver or magnet, depending on trigger type, over the triggers (with the ignition on). You should see strong white sparks at the plugs. That tells you the system is working, then you just need to confirm the flywheel-to-trigger gap is set correctly.

If you have a mag-hole trigger, remove it and twist the gear. Should fire the plugs.
 
Does the magneto have an impulse coupler? If not is the mag switch configured to prevent the mag from firing during cranking?
Tim Andres
 
Thanks all!

So on investigation of the switch, the Plasma is connected to R terminal on the ACS and is therefore grounded on start, so we are trying to start on the Mag alone. The mag does have an impulse coupler so it stands to reason that this mag needs looking into as it is approaching 500 hours. We have reassessed the ACS Service Bulletin and the Inspector is signing that off again.

Next question is whether we swap wires on the switch so that the Mag is grounded on start and we start with the Plasma box, at least to fly her to a workshop and get the mag overhauled.

If you had a 1x mag and 1x Plasma system, which would you start on?
 
Last edited:
my plane was slowly getting harder to start and then it would start when I let go of the key to stop cranking and then it started on both with the last turn off the prop. it was a worn impulse coupling on the left slick mag. I replaced the mag. my mag checks were good when running also

Did the impulse still sound okay (click) when you pass the prop through TDC?
 
Boy , talk about great memory?s, business card or matchbook run thru points brings me back to 50s-60s working on VW Bugs !
 
Thanks all!

So on investigation of the switch, the Plasma is connected to R terminal on the ACS and is therefore grounded on start, so we are trying to start on the Mag alone. The mag does have an impulse coupler so it stands to reason that this mag needs looking into as it is approaching 500 hours. We have reassessed the ACS Service Bulletin and the Inspector is signing that off again.

Next question is whether we swap wires on the switch so that the Mag is grounded on start and we start with the Plasma box, at least to fly her to a workshop and get the mag overhauled.

If you had a 1x mag and 1x Plasma system, which would you start on?

In your initial post, you indicate that you validated each plug on the mag was firing while cranking. You also indicated that the engine only kicks back when starting on the plasma.

Basic troubleshooting: Fuel / Air / Ignition. You confirmed that you get spark on the mag plugs during the starting phase. You also confirmed that the plasma is problematic during start (kicks back - pointing to timing issues), therefore eliminate the plasma during troubleshooting and move on the next two elements - Fuel and Air. Not much sense continuing to troubleshoot the mag, when you have confirmed that it is sparking.

Not saying that the mag isn't your problem, but it seems low on the probability list for the "no start" condition," given the details provided in the first post.

Larry
 
Last edited:
If you had a 1x mag and 1x Plasma system, which would you start on?

I have exactly this with the Bendix version of the ACS switch. I start with both the impulse coupled mag on the "Left", LSE on the "Right". There's a jumper to install/remove on the back of the Bendix switch that either enables/defeats the right side when in "Start" switch position. It's easy to wring out the wiring/jumper if you remove the switch and play with it and a VOM.
 
Young man.

Oops, Did I just tell my age?

No, your still very young. I still have a points file in one tool box that's about 50 years old. I think you can still order them from Snap-On. I liked to use 600-800 wet dry sand paper and then clean up with note-book paper, so you can see the carbon clean a way on the white paper. Then re-set the air gap.
Your just a young guy, "wipper-snapper". Yours, R.E.A. III # 80888
 
So - last night we wired the Plasma unit to the LEFT key position and she started straight away.

Mag drops are fine on both sides, but I did note that the engine skipped a beat when turning the key from the Mag (R) to Plasma (L). It felt almost as though the key was grounding both R and L for a fraction of a second. The Mag is connected to the R terminal with the jumper still in place. If we remove the jumper will that mean that L and R both participate in the start?

My theory is we have a little key issue to sort out and the impulse coupling and mag need a check, as the magneto works when the engine fires but the magneto will not start the engine on its own.

Anyway - I've clearly put this thread in the wrong forum as the Plasma box is fine :D Thank goodness I didn't ring Klaus and have a moan..
 
No, your still very young. I still have a points file in one tool box that's about 50 years old. I think you can still order them from Snap-On. I liked to use 600-800 wet dry sand paper and then clean up with note-book paper, so you can see the carbon clean a way on the white paper. Then re-set the air gap.
Your just a young guy, "wipper-snapper". Yours, R.E.A. III # 80888

Are you saying that everyone doesn't have a points file? My points file is laying in the drawer right next to my dwell meter.
 
So - last night we wired the Plasma unit to the LEFT key position and she started straight away.

Mag drops are fine on both sides, but I did note that the engine skipped a beat when turning the key from the Mag (R) to Plasma (L). It felt almost as though the key was grounding both R and L for a fraction of a second. The Mag is connected to the R terminal with the jumper still in place. If we remove the jumper will that mean that L and R both participate in the start?

My theory is we have a little key issue to sort out and the impulse coupling and mag need a check, as the magneto works when the engine fires but the magneto will not start the engine on its own.

Anyway - I've clearly put this thread in the wrong forum as the Plasma box is fine :D Thank goodness I didn't ring Klaus and have a moan..

I too had the "quick skip" when I had the ACS version of the switch. I kept the ACS terminal back, and just mounted it to the guts and front end of a Bendix switch - voila, problem gone! Good you didn't have to listen to Klaus tell you to get rid of the key switch and use toggles :)
 
Well, we finally fixed the starting.

The mag came up to inspection time (500hr) and... the impulse coupling wasn't engaging.

New springs, capacitor and a few other items and she's running sweet now.

Next to fit a new switch.

:D
 
Back
Top