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  #1  
Old 09-21-2018, 08:10 AM
Towline Towline is offline
 
Join Date: Feb 2018
Location: West Central UK
Posts: 4
Default My O-320 Won't Start

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 by Towline : 09-21-2018 at 08:14 AM.
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  #2  
Old 09-21-2018, 09:18 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 3,117
Default

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
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RV-6A / IO-320, Flying as of 8/2015
RV-10 in progress

Last edited by lr172 : 09-21-2018 at 09:26 AM.
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  #3  
Old 09-21-2018, 09:24 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 3,117
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Quote:
Originally Posted by Towline View Post
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
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RV-10 in progress
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  #4  
Old 09-21-2018, 09:42 AM
Mike S's Avatar
Mike S Mike S is offline
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
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Default Welcome to VAF

Quote:
Originally Posted by Towline View Post
Hi folks - first time posting here
Jon, welcome aboard the good ship VAF
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  #5  
Old 09-21-2018, 09:59 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Read this thread for ideas

http://www.vansairforce.com/communit...d.php?t=163995
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RV-10 in progress
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  #6  
Old 09-21-2018, 10:01 AM
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Mel Mel is online now
 
Join Date: Mar 2005
Location: Dallas area
Posts: 10,081
Default 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.
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North Texas (8TA5)
RV-6 Flying since 1993, 172hp O-320, 3-Blade Catto (since 2003)
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Last edited by Mel : 09-21-2018 at 10:09 AM.
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  #7  
Old 09-21-2018, 11:10 AM
Canadian_JOY Canadian_JOY is offline
 
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 1,748
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Quote:
Originally Posted by Mel View Post
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!
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  #8  
Old 09-21-2018, 11:17 AM
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rocketbob rocketbob is offline
 
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Location: 8I3
Posts: 2,983
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Disconnect the p-lead from the mag, and try to start it on the mag only. That way you can 100% eliminate the switch.
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  #9  
Old 09-22-2018, 05:31 PM
deek deek is offline
 
Join Date: Mar 2013
Location: Flathead Lake Montana - 8S1
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Default

Quote:
Originally Posted by rocketbob View Post
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?
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  #10  
Old 09-22-2018, 05:51 PM
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az_gila az_gila is online now
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
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Quote:
Originally Posted by rocketbob View Post
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?
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