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Engine won't air start

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jetfighterrides

Joined: 02 Dec 2009
Posts: 3
Location: Australia

Posted: Fri Dec 04, 2009 3:41 pm Post subject: Engine won't air start

Our Yak-52(year:1985), still fails to kick over(start) once the air start button is pushed. We simply get a hissing from the starter solenoid valve region, and the prop vibrates, and shutters a little. As a result we have been prop starting (hand swinging) the yak. We have conducted the following maintenance in order to rectify the issue:



1) New Vibrator Box;

2) Changed the starter-solenoid;

3) Listened to the starter air distributor spider, for any obvious air leaks;

4) Listened to the lines to and from the spider, for any obvious air leaks;

5) Sprayed WD-40 in the starter solenoid valve, and exercised it;

6) Both the start Voltage and Amps were sufficient;

7) Activated the starter solenoid override valve switch on the inboard

    firewall; 

 Reset the prop to TDC after an attempted start, then reattempted a start;

9) All starts are conducted with system pressure greater than 50kgf/cmÂ²;  



We still have no joy, and we are running out of options. We are considering replacing or overhauling the air distributor spider?



Any thoughts would be greatly appreciated.

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_________________
Regards

Matthew Doherty

Pilot/owner

www.jetfighterrides.com.au

ronwasson

Joined: 05 Sep 2007
Posts: 30

Posted: Fri Dec 04, 2009 3:56 pm Post subject: Engine won't air start

Stuck valve maybe. Prop it thru once to get it off the bad cylinder. If the starter works for 2 or 3 blades than stops that is a sign . It stops on the bad cylinder and hisses out he exhaust with a hung valve.  Getting the motor running and warmed up with break the valve loose.  Running the motor once a week will stop it.



On Dec 4, 2009, at 5:41 PM, jetfighterrides wrote:



 	  Quote: 	
		   

 

 Our Yak-52(year:1985), still fails to kick over(start) once the air start button is pushed. We simply get a hissing from the starter solenoid valve region, and the prop vibrates, and shutters a little. As a result we have been prop starting (hand swinging) the yak. We have conducted the following maintenance in order to rectify the issue:

 

 1) New Vibrator Box;

 2) Changed the starter-solenoid;

 3) Listened to the starter air distributor spider, for any obvious air leaks;

 4) Listened to the lines to and from the spider, for any obvious air leaks;

 5) Sprayed WD-40 in the starter solenoid valve, and exercised it;

 6) Both the start Voltage and Amps were sufficient;

 7) Activated the starter solenoid override valve switch on the inboard

    firewall; 

  Reset the prop to TDC after an attempted start, then reattempted a start;

 9) All starts are conducted with system pressure greater than 50kgf/cmÂ²;  

 

 We still have no joy, and we are running out of options. We are considering replacing or overhauling the air distributor spider?

 

 Any thoughts would be greatly appreciated.

 

 --------

 Regards

 

 Matthew Doherty

 

 Pilot/owner

 

 www.jetfighterrides.com.au

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p 76243#276243

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dsavarese0812(at)bellsout
Guest

Posted: Fri Dec 04, 2009 8:06 pm Post subject: Engine won't air start

Did you check the hose from the firewall to the air start  distributor?  I have seen these hoses split.  The hissing sound sounds  like it is coming from the from the air start solenoid when in fact it is coming  right out of the fractured hose.  If you remove the hose from the firewall  and press the air start button, you should have quite a bit of pressure coming  out of the firewall fitting.  If you do have adequate air pressure, I would  suspect a damaged air start distributor which has an internal spring which keeps  pressure on the internal section. 

 Dennis 

 [quote]   ---

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yakplt(at)yahoo.com
Guest

Posted: Sat Dec 05, 2009 4:18 pm Post subject: Engine won't air start

It does indeed sound like an air distributor problem, God Help You.  I say that because working on that thing is a nightmare.  Before you pull this thing out and start into it, I would be darn sure..  Excuse me.... DAMN sure that it is the problem.  

  

 First, make sure you do not have an exhaust or intake valve stuck open.  If you happened to have something like that happen, and the air distributor happened to be feeding air into that cylinder, it would stop dead.  Try moving the prop to different positions and then try to start it.  Don't always go to TDC on number 4, move it all over the place and see if you get the exact same results.  

  

 If you do.....

  

 I would obtain a source of 730 PSI air, or nitrogen... (NOT PURE OXYGEN of course) and connect it through an adapter to go  DIRECTLY to the line going right into the air distributor on the engine.  I mean bypass EVERYTHING and feed the air directly to the air distributor through a manually controlled valve on an external bottle.  Basically bypass the whole freaking airplane system and run air from an external bottle right to the engine air distributor and then see if the engine cranks.  You're not trying to start it here, just to crank it.  No ignition required.  

  

 If the engine does not turn at this point, you can be pretty darn sure you have nailed the problem down.  If it DOES crank, then you have missed something.  Possibly a clogged line, or stuck check valve, any number of things... but man oh man, be SURE before you mess with that air-distributor! !! !!!!!!!!!!!!!!!!   

  

 Some notes:  The air distributor is connected to a reduction gearing arrangement located behind the cover for the tach drive generator.  By chance... has anyone been messing around in the tach drive generator area or maybe had the cover off messing around?  If so, then that would be the problem.  Once the air distributor gets "out of time" it will do pretty much exactly what you are talking about.  You will have to re-time the thing and that is a real pain in the tail.  The procedure to do it is in the Russian maint. manuals, but again a big warning, make darn sure this is the issue before pulling the cover on the air distributor.  

  

 Anyway, that's a start.  Possibly Dennis has the text to align that thing handy.  I do not right now, but you are going to need it if that is indeed the problem.  Hopefully it is NOT, and honestly the odds are fair to good that it isn't.  

  

 Good Luck, 

  

 Mark Bitterlich

  

 



--- On Fri, 12/4/09, jetfighterrides <jetfighterrides(at)gmail.com> wrote:



  	  Quote: 	
		  

From: jetfighterrides <jetfighterrides(at)gmail.com>

Subject: Engine won't air start

To: yak-list(at)matronics.com

Date: Friday, December 4, 2009, 6:41 PM



 --> Yak-List message posted by: "jetfighterrides" <jetfighterrides(at)gmail.com (jetfighterrides(at)gmail.com)>



Our Yak-52(year:1985), still fails to kick over(start) once the air start button is pushed. We simply get a hissing from the starter solenoid valve region, and the prop vibrates, and shutters a little. As a result we have been prop starting (hand swinging) the yak. We have conducted the following maintenance in order to rectify the issue:



1) New Vibrator Box;

2) Changed the starter-solenoid;

3) Listened to the starter air distributor spider, for any obvious air leaks;

4) Listened to the lines to and from the spider, for any obvious air leaks;

5) Sprayed WD-40 in the starter solenoid valve, and exercised it;

6) Both the start Voltage and Amps were sufficient;

7) Activated the starter solenoid  override valve switch on the inboard

    firewall; 

 Reset the prop to TDC after an attempted start, then reattempted a start;

9) All starts are conducted with system pressure greater than 50kgf/cmÂ²;  



We still have no joy, and we are running out of options. We are considering replacing or overhauling the air distributor spider?



Any thoughts would be greatly appreciated.



--------

Regards



Matthew Doherty



Pilot/owner



www.jetfighterrides.com.au





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=276243#276243





   --> 



	
 [quote][b]

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Mozam

Joined: 24 Nov 2006
Posts: 85

Posted: Sun Dec 06, 2009 6:14 am Post subject: Re: Engine won't air start

I experienced the exact same symptoms several years ago.



I had taken my tach generator unit (a UMA tach generator) off the air start assembly to repair it. When I removed it I failed to notice that a washer (spacer) had fallen out that was under the tach generator screw on cap.



I reinstalled the tach generator without this washer and then had the same problem you have. Air would get to the air start assembly, but not to the cylinders.



After a LONG period of head scratching, and after finding the washer on the hanger floor, I finally solved the problem by replacing the washer.



Following this episode I experimented with different thickness spacers and found what seemed to work best.



I hope your problem is as easy to fix.  Best of luck,

Steve Dalton

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