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914 partial power failure

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john firth

Joined: 29 Jan 2011
Posts: 11
Location: Yorkshire England

Posted: Sun Jan 30, 2011 9:48 pm Post subject: 914 partial power failure

Hello all, I have a 914 fitted to a mono wheel Europa. a couple of weeks ago I suffered a partial power failure on take off and had to land immediately. After changing the fuel filters and cleaning out the carbs she ran fine for three hours and five take offs and then failed again and now has symptom's on ground runs which are:-

starts well and runs smooth till 2800ish rpm

can be made to go to 5000plus but runs rough and mag drops 600

I have checked the following:-

Replaced the whole fuel system except pumps, selector valve and tank fittings but removed and checked them all.

Done Rotax fuel flow check at plus 0.5 bar simulated air box pressure giving 10psi fuel pressure and delivering 70litres/hour on each pump.

Checked airbox pressure v fuel pressure when engine running 4psi

Checked float bowls for dirt, blown out jets, checked needle valves and float level- all appear ok.

Checked slide and diaphragm for leaks and smooth operation.

Checked all small air pipes for leaks and blockage and carb mounting rubbers for splits.

Checked plugs- all look OK with light brown deposits slightly white but am running Avgas at the moment. (she runs the same on Mogas) and swopped the top two plugs with each other at both sides.

When run to 5000rpm, airbox pressure rises to 1.1b and fuel increases to 1,4b.

TCU lights normal on power up and servo can be heard operating.I will check waste gate arm moving tomorrow.

I could use some ideas from the wealth of experience out there.

Regards, john.

gpabruce(at)gmail.com
Guest

Posted: Mon Jan 31, 2011 12:10 am Post subject: 914 partial power failure

It may very well be in ignition this time, wires mags breaking down, moisture in mags, and even mechanical issues valves floating, sticking etc . . yes I know you had fuel issues too and you looked at the plugs but you may have multiple intermittent problems on multiple systems that are more difficult to isolate. Don't get hungup on any one idea. Keep an open mind and try to force a failure and then isolate that failure. Fix it and then see if there is another problem . . could be. As I said you may have multiple things failing under temp and pressure and then they heal up when the stress is relieved. Make sense? The difficult porblems are also the fun ones. 

   

 Also don't forget to check carb heat . . . carb icing can cause you to pull your hair out plus it can be damned dangerous. Yeh I know it ain't sposed to happen on take off . . . shit happens though. 

  

 Do you have the same mag drop on both mags or more on just one mag? Mag drops don't indicate a fuel problem but more of Ignition and or mechanical. Roughness can be fuel, ignition, air or mechanical or worse case . . all of the above.  Try to isolate with mag check first as much as possible then use compression test and temperature stress test. By doing these tests, you may see a pattern or a common cylinder that is losing power (loss of power is indicated by a lower temperature hence the CHT temp test or EGT test or both) If you have quad temp like I do, you can analyze it from the cockpit in flight or on the ground . . . what's four temps among friends, right?  

   

 Don't let multiple intermittent problems confuse you like it does a lot of people. Just because you had a fuel issue doesn't mean you don't still have problems in other systems. Have you had a lot of weather? This is what separates the men from the boys in trouble shooting. You will need to make the culpret(s) break down if possible by putting the engine under stress (load) and temperature. Better on the ground than in the air.  You may need to do a compression test after the engine is warmed. Do you know how to do that?  Do a comp test early on before getting too deep. A comp test will show valve and ring problems usually unless valves are floating, it won't show that.

   

 Is malfunction on same cyls all the time? Run engine up with cowling off under load and high RPM to achieve maximum roughness and then monitor temps of each cylinder as follows. Let engine heat up and then check differential cyl temperature or if you have four egt's record them, is it aircooled? If yes use a temp wand to immediately check temp on all four cyls after shut down or have someone check cyl temps while running under load . . . caution about spinning prop. I don't know if a 914 is aircooled or watercooled. Watercooled is more difficult to trouble shoot by temp. Use temp wand or photopyrometer on individual exhaust pipes if water cooled. You may be able to detect a difference in temp right on the sparkplug. Compare apples to apples, check all top and compare or all bottom and compare.  

   

 Good luck and let me know . . . 

 Bruce

 On Sun, Jan 30, 2011 at 9:48 PM, john firth <firth942(at)btinternet.com (firth942(at)btinternet.com)> wrote:

 [quote]--> RotaxEngines-List message posted by: "john firth" <firth942(at)btinternet.com (firth942(at)btinternet.com)>

 

Hello all, I have a 914 fitted to a mono wheel Europa. a couple of weeks ago I suffered a partial power failure on take off and had to land immediately. After changing the fuel filters and cleaning out the carbs she ran fine for three hours and five take offs and then failed again and now has symptom's on ground runs which are:-

 starts well and runs smooth till 2800ish rpm

can be made to go to 5000plus but runs rough and mag drops 600

I have checked the following:-

Replaced the whole fuel system except pumps, selector valve and tank fittings but removed and checked them all.

 Done Rotax fuel flow check at plus 0.5 bar simulated air box pressure giving 10psi fuel pressure and delivering 70litres/hour on each pump.

Checked airbox pressure v fuel pressure when engine running 4psi

Checked float bowls for dirt, blown out jets, checked needle valves and float level- all appear ok.

 Checked slide and diaphragm for leaks and smooth operation.

Checked all small air pipes for leaks and blockage and carb mounting rubbers for splits.

Checked plugs- all look OK with light brown deposits slightly white but am running Avgas at the moment. (she runs the same on Mogas) and swopped the top two plugs with each other at both sides.

 When run to 5000rpm, airbox pressure rises to 1.1b and fuel increases to 1,4b.

TCU lights normal on power up and servo can be heard operating.I will check waste gate arm moving tomorrow.

I could use some ideas from the wealth of experience out there.

 Regards, john.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=329052#329052



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grahamsingleton(at)btinte
Guest

Posted: Mon Jan 31, 2011 12:42 am Post subject: 914 partial power failure

John

Do you have a radiation pyrometer? I have one but maybe a bit far away in Derbyshire. Quick way to check EGT/CHT

Graham

From: john firth <firth942(at)btinternet.com>

To: rotaxengines-list(at)matronics.com

Sent: Monday, 31 January, 2011 5:48:56

Subject: 914 partial power failure

--> RotaxEngines-List message posted by: "john firth" <firth942(at)btinternet.com (firth942(at)btinternet.com)>

Hello all, I have a 914 fitted to a mono wheel Europa. a couple of weeks ago I suffered a partial power failure on take off and had to land immediately. After changing the fuel filters and cleaning out the carbs she ran fine for three hours and five take offs and then failed again and now has symptom's on ground runs which are:-

starts well and runs smooth till 2800ish rpm

can be made to go to 5000plus but runs rough and mag drops 600

I have checked the following:-

Replaced the whole fuel system except pumps, selector valve and tank fittings but removed and checked them all.

Done Rotax fuel flow check at plus 0.5 bar simulated air box pressure giving 10psi fuel pressure and delivering 70litres/hour on each pump.

Checked airbox pressure v fuel pressure when engine running 4psi

Checked float bowls for dirt, blown out  jets, checked needle valves and float level- all appear ok.

Checked slide and diaphragm for leaks and smooth operation.

Checked all small air pipes for leaks and blockage and carb mounting rubbers for splits.

Checked plugs- all look OK with light brown deposits slightly white but am running Avgas at the moment. (she runs the same on Mogas) and swopped the top two plugs with each other at both sides.

When run to 5000rpm, airbox pressure rises to 1.1b and fuel increases to 1,4b.

TCU lights normal on power up and servo can be heard operating.I will check waste gate arm moving tomorrow.

I could use some ideas from the wealth of experience out there.

Regards, john.

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=329052#329========================http://www.matronics.com/N=   -->

john firth

Joined: 29 Jan 2011
Posts: 11
Location: Yorkshire England

Posted: Mon Jan 31, 2011 2:21 am Post subject: Re: 914 partial power failure

Thanks Bruce, I did compression check and got just one cylinder down by 5psi, others at 130psi engine was warm.

looks like i need some temp measuring devices but panel on my plane is very full.

Cheers, john.

ptag.dev(at)tiscali.co.uk
Guest

Posted: Mon Jan 31, 2011 2:53 am Post subject: 914 partial power failure

Hi! John

Have you checked that :-

 

a)Â  The choke cable is allowing both levers to return to disused position?

b) The ignition grounding hasnâ€™t any glitches anywhere (intermittent short out through the odd single strand of wire)

c) Did you check the electric pump thimble filters for crud.(be very carefull when getting them out to inspect and returning them after since it is impossible to get replacements without buying a new pump!)

 

Regards

Bob Harrison G-PTAG

 

 

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of GRAHAM SINGLETON

Sent: 31 January 2011 08:39

To: rotaxengines-list(at)matronics.com

Subject: Re: 914 partial power failure

 

John

Do you have a radiation pyrometer? I have one but maybe a bit far away in Derbyshire. Quick way to check EGT/CHT

Graham



 



From: john firth <firth942(at)btinternet.com>

To: rotaxengines-list(at)matronics.com

Sent: Monday, 31 January, 2011 5:48:56

Subject: 914 partial power failure



--> RotaxEngines-List message posted by: "john firth" <firth942(at)btinternet.com (firth942(at)btinternet.com)>



Hello all, I have a 914 fitted to a mono wheel Europa. a couple of weeks ago I suffered a partial power failure on take off and had to land immediately. After changing the fuel filters and cleaning out the carbs she ran fine for three hours and five take offs and then failed again and now has symptom's on ground runs which are:-

starts well and runs smooth till 2800ish rpm

can be made to go to 5000plus but runs rough and mag drops 600

I have checked the following:-

Replaced the whole fuel system except pumps, selector valve and tank fittings but removed and checked them all.

Done Rotax fuel flow check at plus 0.5 bar simulated air box pressure giving 10psi fuel pressure and delivering 70litres/hour on each pump.

Checked airbox pressure v fuel pressure when engine running 4psi

Checked float bowls for dirt, blown out jets, checked needle valves and float level- all appear ok.

Checked slide and diaphragm for leaks and smooth operation.

Checked all small air pipes for leaks and blockage and carb mounting rubbers for splits.

Checked plugs- all look OK with light brown deposits slightly white but am running Avgas at the moment. (she runs the same on Mogas) and swopped the top two plugs with each other at both sides.

When run to 5000rpm, airbox pressure rises to 1.1b and fuel increases to 1,4b.

TCU lights normal on power up and servo can be heard operating.I will check waste gate arm moving tomorrow.

I could use some ideas from the wealth of experience out there.

Regards, john.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=329052#329======================== href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/contribution =========== 



  [quote][b]

grahamsingleton(at)btinte
Guest

Posted: Mon Jan 31, 2011 3:22 am Post subject: 914 partial power failure

John

4 EGTs would be good, 2 CHT OK. Do you have an engine monitor?

Graham



From: john firth <firth942(at)btinternet.com>

To: rotaxengines-list(at)matronics.com

Sent: Monday, 31 January, 2011 10:21:57

Subject: Re: 914 partial power failure



--> RotaxEngines-List message posted by: "john firth" <firth942(at)btinternet.com (firth942(at)btinternet.com)>



Thanks Bruce, I did compression check and got just one cylinder down by 5psi, others at 130psi engine was warm.

looks like i need some temp measuring devices but panel on my plane is very full.

Cheers, john.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=329060#329060





http://forums.matronics.com

john firth

Joined: 29 Jan 2011
Posts: 11
Location: Yorkshire England

Posted: Mon Jan 31, 2011 9:42 am Post subject: Re: 914 partial power failure

Bob, I have checked the choke levers and they're ok and the thimble filters look clean visually but i could'nt get them out. The pumps are flowing over 100litres an hour each with no back pressure so not too suspicious there and fuel pressure stays good while running up to 5000 rpm 3-4psi above airbox.

I am now starting to delve into the wiring.

Graham, a radiation pyrometer would be very useful, if I cannot source one nearby I will take you up on your kind offer.

Regards, john.

gpabruce(at)gmail.com
Guest

Posted: Mon Jan 31, 2011 12:43 pm Post subject: 914 partial power failure

John, did you get my first response I sent you? I'll resend it to you. 

  They are also called Photopyrometers or infrared temp indicators. You can get them at Harbor Freight and most home suppy stores. You can also find a stick type thermomenter in Martha Stewart ware or your napa auto store. Walmart probably has both types too. It doesn't have to be precise, you are looking for difference as opposed to absolute. 

 

  

 Bruce

  

  

 Here is a copy of my first response to you. I pretty much covered all the bases for you, Fule Air, Ignition, Mechanical, if you are interested, I didn't hear back.   



  	  Quote: 	
		   b d to rotaxengines-l. 

 show details 12:07 AM (12 hours ago) 

  

 It may very well be in ignition this time, wires mags breaking down, moisture in mags, and even mechanical issues valves floating, sticking etc . . yes I know you had fuel issues too and you looked at the plugs but you may have multiple intermittent problems on multiple systems that are more difficult to isolate. Don't get hungup on any one idea. Keep an open mind and try to force a failure and then isolate that failure. Fix it and then see if there is another problem . . could be. As I said you may have multiple things failing under temp and pressure and then they heal up when the stress is relieved. Make sense? The difficult porblems are also the fun ones. 

    

 Also don't forget to check carb heat . . . carb icing can cause you to pull your hair out plus it can be damned dangerous. Yeh I know it ain't sposed to happen on take off . . . shit happens though. 

   

 Do you have the same mag drop on both mags or more on just one mag? Mag drops don't indicate a fuel problem but more of Ignition and or mechanical. Roughness can be fuel, ignition, air or mechanical or worse case . . all of the above.  Try to isolate with mag check first as much as possible then use compression test and temperature stress test. By doing these tests, you may see a pattern or a common cylinder that is losing power (loss of power is indicated by a lower temperature hence the CHT temp test or EGT test or both) If you have quad temp like I do, you can analyze it from the cockpit in flight or on the ground . . . what's four temps among friends, right?  

    

 Don't let multiple intermittent problems confuse you like it does a lot of people. Just because you had a fuel issue doesn't mean you don't still have problems in other systems. Have you had a lot of weather? This is what separates the men from the boys in trouble shooting. You will need to make the culpret(s) break down if possible by putting the engine under stress (load) and temperature. Better on the ground than in the air.  You may need to do a compression test after the engine is warmed. Do you know how to do that?  Do a comp test early on before getting too deep. A comp test will show valve and ring problems usually unless valves are floating, it won't show that.

    

 Is malfunction on same cyls all the time? Run engine up with cowling off under load and high RPM to achieve maximum roughness and then monitor temps of each cylinder as follows. Let engine heat up and then check differential cyl temperature or if you have four egt's record them, is it aircooled? If yes use a temp wand to immediately check temp on all four cyls after shut down or have someone check cyl temps while running under load . . . caution about spinning prop. I don't know if a 914 is aircooled or watercooled. Watercooled is more difficult to trouble shoot by temp. Use temp wand or photopyrometer on individual exhaust pipes if water cooled. You may be able to detect a difference in temp right on the sparkplug. Compare apples to apples, check all top and compare or all bottom and compare.  

    

 Good luck and let me know . . . 

 Bruce

  

	
 On Mon, Jan 31, 2011 at 9:42 AM, john firth <firth942(at)btinternet.com (firth942(at)btinternet.com)> wrote:

  

  	  Quote: 	
		  --> RotaxEngines-List message posted by: "john firth" <firth942(at)btinternet.com (firth942(at)btinternet.com)>   

 Bob, I have checked the choke levers and they're ok and the thimble filters look clean visually but i could'nt get them out. The pumps are flowing over 100litres an hour each with no back pressure so not too suspicious there and fuel pressure stays good while running up to 5000 rpm 3-4psi above airbox.

  I am now starting to delve into the wiring.

 Graham, a radiation pyrometer would be very useful, if I cannot source one nearby I will take you up on your kind offer.

 Regards, john.

  

  

  

  

 Read this topic online here:

  

 http://forums.matronics.com/viewtopic.php?p=329090#329090

  

  

  

  

  

  

  

 =============

 gines-List" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List

 =============

 lank">http://forums.matronics.com

 =============

  Dralle, List Admin.

 get="_blank">http://www.matronics.com/contribution

 =============

  

  

  

  

	
  

  [quote][b]

john firth

Joined: 29 Jan 2011
Posts: 11
Location: Yorkshire England

Posted: Mon Jan 31, 2011 3:05 pm Post subject: 914 partial power failure

Hello Bruce, I did respond but got a undeliverable mail message from postmaster. anyway here is a copy :-  Thanks Bruce, I did compression check and got just one cylinder down by 5psi, others at 130psi engine was warm.

looks like i need some temp measuring devices but panel on my plane is very full.-: Also Graham Singleton has offered to lend me his.

Regards, john.

[quote]John, did you get my first response I sent you? I'll resend it to you.

  They are also called Photopyrometers or infrared temp indicators. You can get them at Harbor Freight and most home suppy stores. You can also find a stick type thermomenter in Martha Stewart ware or your napa auto store. Walmart probably has both types too. It doesn't have to be precise, you are looking for difference as opposed to absolute. 

 

  

 Bruce

  

  

 Here is a copy of my first response to you. I pretty much covered all the bases for you, Fule Air, Ignition, Mechanical, if you are interested, I didn't hear back.   



  	  Quote: 	
		   b d to rotaxengines-l. 

 show details 12:07 AM (12 hours ago) 

  

 It may very well be in ignition this time, wires mags breaking down, moisture in mags, and even mechanical issues valves floating, sticking etc . . yes I know you had fuel issues too and you looked at the plugs but you may have multiple intermittent problems on multiple systems that are more difficult to isolate. Don't get hungup on any one idea. Keep an open mind and try to force a failure and then isolate that failure. Fix it and then see if there is another problem . . could be. As I said you may have multiple things failing under temp and pressure and then they heal up when the stress is relieved. Make sense? The difficult porblems are also the fun ones. 

    

 Also don't forget to check carb heat . . . carb icing can cause you to pull your hair out plus it can be damned dangerous. Yeh I know it ain't sposed to happen on take off . . . shit happens though. 

   

 Do you have the same mag drop on both mags or more on just one mag? Mag drops don't indicate a fuel problem but more of Ignition and or mechanical. Roughness can be fuel, ignition, air or mechanical or worse case . . all of the above.  Try to isolate with mag check first as much as possible then use compression test and temperature stress test. By doing these tests, you may see a pattern or a common cylinder that is losing power (loss of power is indicated by a lower temperature hence the CHT temp test or EGT test or both) If you have quad temp like I do, you can analyze it from the cockpit in flight or on the ground . . . what's four temps among friends, right?  

    

 Don't let multiple intermittent problems confuse you like it does a lot of people. Just because you had a fuel issue doesn't mean you don't still have problems in other systems. Have you had a lot of weather? This is what separates the men from the boys in trouble shooting. You will need to make the culpret(s) break down if possible by putting the engine under stress (load) and temperature. Better on the ground than in the air.  You may need to do a compression test after the engine is warmed. Do you know how to do that?  Do a comp test early on before getting too deep. A comp test will show valve and ring problems usually unless valves are floating, it won't show that.

    

 Is malfunction on same cyls all the time? Run engine up with cowling off under load and high RPM to achieve maximum roughness and then monitor temps of each cylinder as follows. Let engine heat up and then check differential cyl temperature or if you have four egt's record them, is it aircooled? If yes use a temp wand to immediately check temp on all four cyls after shut down or have someone check cyl temps while running under load . . . caution about spinning prop. I don't know if a 914 is aircooled or watercooled. Watercooled is more difficult to trouble shoot by temp. Use temp wand or photopyrometer on individual exhaust pipes if water cooled. You may be able to detect a difference in temp right on the sparkplug. Compare apples to apples, check all top and compare or all bottom and compare.  

    

 Good luck and let me know . . . 

 Bruce

  

	
 On Mon, Jan 31, 2011 at 9:42 AM, john firth <firth942(at)btinternet.com (firth942(at)btinternet.com)> wrote:

  

  	  Quote: 	
		  --> RotaxEngines-List message posted by: "john firth" <firth942(at)btinternet.com (firth942(at)btinternet.com)>   

 Bob, I have checked the choke levers and they're ok and the thimble filters look clean visually but i could'nt get them out. The pumps are flowing over 100litres an hour each with no back pressure so not too suspicious there and fuel pressure stays good while running up to 5000 rpm 3-4psi above airbox.

  I am now starting to delve into the wiring.

 Graham, a radiation pyrometer would be very useful, if I cannot source one nearby I will take you up on your kind offer.

 Regards, john.

  

  

  

  

 Read this topic online here:

  

 http://forums.matronics.com/viewtopic.php?p=329090#329090

  

  

  

  

  

  

  

 ============= gines-List" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List ============= lank">http://forums.matronics.com =============  Dralle, List Admin. get="_blank">http://www.matronics.com/contribution =============  

  

  

  

	
  

   	  Quote: 	
		  

	
[b]

grahamsingleton(at)btinte
Guest

Posted: Mon Jan 31, 2011 3:42 pm Post subject: 914 partial power failure

with the right temptation you might entice me towards Burn airfield, is ot nearer than Sherburn in Elmet?

Haven't seen any of those people in 20 years!

Graham

From: john firth <firth942(at)btinternet.com>

To: rotaxengines-list(at)matronics.com

Sent: Monday, 31 January, 2011 17:42:38

Subject: Re: 914 partial power failure

--> RotaxEngines-List message posted by: "john firth"  <firth942(at)btinternet.com (firth942(at)btinternet.com)>

Bob, I have checked the choke levers and they're ok and the thimble filters look clean visually but i could'nt get them out. The pumps are flowing over 100litres an hour each with no back pressure so not too suspicious there and fuel pressure stays good while running up to 5000 rpm 3-4psi above airbox.

I am now starting to delve into the wiring.

Graham, a radiation pyrometer would be very useful, if I cannot source one nearby I will take you up on your kind offer.

Regards, john.

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=329090#3290========================http://forums.matronics.com[b]http://ww=======================

 [quote][b]

john firth

Joined: 29 Jan 2011
Posts: 11
Location: Yorkshire England

Posted: Mon Jan 31, 2011 4:04 pm Post subject: 914 partial power failure

Hello Graham, not much difference in distance between Burn and Sherburn from yours. My aircraft is actually at Barnsley at the moment. I will give you a call when I know my movements this next few days but I am working until saturday.Regards, john.

On 31 Jan 2011, at 23:38, GRAHAM SINGLETON wrote:

 	  Quote: 	
		  with the right temptation you might entice me towards Burn airfield, is ot nearer than Sherburn in Elmet?

Haven't seen any of those people in 20 years!

Graham

From: john firth <firth942(at)btinternet.com (firth942(at)btinternet.com)>

To: rotaxengines-list(at)matronics.com (rotaxengines-list(at)matronics.com)

Sent: Monday, 31 January, 2011 17:42:38

Subject: Re: 914 partial power failure



--> RotaxEngines-List message posted by: "john firth" <firth942(at)btinternet.com (firth942(at)btinternet.com)>



Bob, I have checked the choke levers and they're ok and the thimble filters look clean visually but i could'nt get them out. The pumps are flowing over 100litres an hour each with no back pressure so not too suspicious there and fuel pressure stays good while running up to 5000 rpm 3-4psi above airbox.

I am now starting to delve into the wiring.

Graham, a radiation pyrometer would be very useful, if I cannot source one nearby I will take you up on your kind offer.

Regards, john.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=329090#3290========================http://forums.matronics.comhttp://ww=======================









 	  Quote: 	
		  [b]



href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matronics.com/Navigator?RotaxEngines-List

href="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/contribution



	
[/b]

	


 [quote][b]

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Feb 01, 2011 12:54 pm Post subject: 914 partial power failure

I wouldn’t believe the static compression test I’ve seen them lie too many times..  Best to do a differential test.  

Noel

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of john firth

Sent: January 31, 2011 7:28 PM

To: rotaxengines-list(at)matronics.com

Subject: Re: Re: 914 partial power failure

Hello Bruce, I did respond but got a undeliverable mail message from postmaster. anyway here is a copy :-  Thanks Bruce, I did compression check and got just one cylinder down by 5psi, others at 130psi engine was warm.

looks like i need some temp measuring devices but panel on my plane is very full.-: Also Graham Singleton has offered to lend me his.

Regards, john.

John, did you get my first response I sent you? I'll resend it to you.

They are also called Photopyrometers or infrared temp indicators. You can get them at Harbor Freight and most home suppy stores. You can also find a stick type thermomenter in Martha Stewart ware or your napa auto store. Walmart probably has both types too. It doesn't have to be precise, you are looking for difference as opposed to absolute. 

Bruce

Here is a copy of my first response to you. I pretty much covered all the bases for you, Fule Air, Ignition, Mechanical, if you are interested, I didn't hear back. 

 	  Quote: 	

b d to rotaxengines-l. 

show details 12:07 AM (12 hours ago) 

It may very well be in ignition this time, wires mags breaking down, moisture in mags, and even mechanical issues valves floating, sticking etc . . yes I know you had fuel issues too and you looked at the plugs but you may have multiple intermittent problems on multiple systems that are more difficult to isolate. Don't get hungup on any one idea. Keep an open mind and try to force a failure and then isolate that failure. Fix it and then see if there is another problem . . could be. As I said you may have multiple things failing under temp and pressure and then they heal up when the stress is relieved. Make sense? The difficult porblems are also the fun ones. 

Also don't forget to check carb heat . . . carb icing can cause you to pull your hair out plus it can be damned dangerous. Yeh I know it ain't sposed to happen on take off . . . shit happens though. 

Do you have the same mag drop on both mags or more on just one mag? Mag drops don't indicate a fuel problem but more of Ignition and or mechanical. Roughness can be fuel, ignition, air or mechanical or worse case . . all of the above.  Try to isolate with mag check first as much as possible then use compression test and temperature stress test. By doing these tests, you may see a pattern or a common cylinder that is losing power (loss of power is indicated by a lower temperature hence the CHT temp test or EGT test or both) If you have quad temp like I do, you can analyze it from the cockpit in flight or on the ground . . . what's four temps among friends, right?  

Don't let multiple intermittent problems confuse you like it does a lot of people. Just because you had a fuel issue doesn't mean you don't still have problems in other systems. Have you had a lot of weather? This is what separates the men from the boys in trouble shooting. You will need to make the culpret(s) break down if possible by putting the engine under stress (load) and temperature. Better on the ground than in the air.  You may need to do a compression test after the engine is warmed. Do you know how to do that?  Do a comp test early on before getting too deep. A comp test will show valve and ring problems usually unless valves are floating, it won't show that.

Is malfunction on same cyls all the time? Run engine up with cowling off under load and high RPM to achieve maximum roughness and then monitor temps of each cylinder as follows. Let engine heat up and then check differential cyl temperature or if you have four egt's record them, is it aircooled? If yes use a temp wand to immediately check temp on all four cyls after shut down or have someone check cyl temps while running under load . . . caution about spinning prop. I don't know if a 914 is aircooled or watercooled. Watercooled is more difficult to trouble shoot by temp. Use temp wand or photopyrometer on individual exhaust pipes if water cooled. You may be able to detect a difference in temp right on the sparkplug. Compare apples to apples, check all top and compare or all bottom and compare.  

Good luck and let me know . . . 

Bruce

On Mon, Jan 31, 2011 at 9:42 AM, john firth <firth942(at)btinternet.com (firth942(at)btinternet.com)> wrote:

 	  Quote: 	

--> RotaxEngines-List message posted by: "john firth" <firth942(at)btinternet.com (firth942(at)btinternet.com)> 

Bob, I have checked the choke levers and they're ok and the thimble filters look clean visually but i could'nt get them out. The pumps are flowing over 100litres an hour each with no back pressure so not too suspicious there and fuel pressure stays good while running up to 5000 rpm 3-4psi above airbox.

I am now starting to delve into the wiring.

Graham, a radiation pyrometer would be very useful, if I cannot source one nearby I will take you up on your kind offer.

Regards, john.

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Feb 02, 2011 12:55 pm Post subject: Re: 914 partial power failure

I agree with Noel.



A static compression test is fine for an automobile, but not

an aircraft engine. Rotax wants a differential leak test, and that's what

the A&Ps also want to see to help solve your problem.

_________________
Ira N224XS

gpabruce(at)gmail.com
Guest

Posted: Wed Feb 02, 2011 5:44 pm Post subject: 914 partial power failure

Differential are fine, and isolate a problem if there is one but dynamic tests, which are what auto test are, is better than doing nothing and will give one a pass or fail real quick. They work fine and are acceptable for a quick test to see if there is a problem or not. I carry one with me because no compressed air is needed in the boonies. I'm an old A&P. More information is better than less. 

   

 Bruce 

 On Wed, Feb 2, 2011 at 12:55 PM, rampil <ira.rampil(at)gmail.com (ira.rampil(at)gmail.com)> wrote:

 [quote]--> RotaxEngines-List message posted by: "rampil" <ira.rampil(at)gmail.com (ira.rampil(at)gmail.com)>

 

I agree with Noel.



A static compression test is fine for an automobile, but not

an aircraft engine. Rotax wants a differential leak test, and that's what

the A&Ps also want to see to help solve your problem.

 

--------

Ira N224XS





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