X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 23 May 2012 11:17:45 -0400 Message-ID: X-Original-Return-Path: Received: from nm3-vm3.bullet.mail.ne1.yahoo.com ([98.138.91.133] verified) by logan.com (CommuniGate Pro SMTP 5.4.5) with SMTP id 5555304 for lml@lancaironline.net; Wed, 23 May 2012 08:49:29 -0400 Received-SPF: none receiver=logan.com; client-ip=98.138.91.133; envelope-from=casey.gary@yahoo.com Received: from [98.138.90.55] by nm3.bullet.mail.ne1.yahoo.com with NNFMP; 23 May 2012 12:48:55 -0000 Received: from [98.138.89.195] by tm8.bullet.mail.ne1.yahoo.com with NNFMP; 23 May 2012 12:48:54 -0000 Received: from [127.0.0.1] by omp1053.mail.ne1.yahoo.com with NNFMP; 23 May 2012 12:48:54 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 962215.91177.bm@omp1053.mail.ne1.yahoo.com Received: (qmail 93947 invoked by uid 60001); 23 May 2012 12:48:54 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=HGRcS6/jf+ncRIyy7PEBHOQT98Crtz5R+6IgEwgHbqUBsDlPmfNk8NmMEoCFB+E5SgsARa/7VhF5WDGqa7BglmlpLH3AA3BgZf9hzDNAaDTppjn5NlJoAdiu+UFEm3bnOuwWyNz4Pawy0vH/zhEP0BwdApu4IKex5A/Ri/Zkqqg=; X-YMail-OSG: ZwBVRngVM1kxxoSYiMu0fqVXACRAshmn60Fv3KB9YB7T7CK C7Gd_BHtp7rLxYBtQRmIcsMJ8vU2R_KN0VYQBTxD1JPcJRZ_AV6xeJEW8Qo0 wHF_NYEDjEXQ.SezVhv.cJ4Twsje0fLpwkxeYkAs8wkHtZZWoUl_pO3KsORH bH3ef2HIK3a4OYA3GnaK3VtYbp4seCysMWrz4Hf2z93NkXwvm5HADWDEoNid .Y4yC9P4MPEUqBtoA8tsu_uCcQ7axAkzd0YnQqX1pJch1jgqbCrohsz.wxa3 9EH7XBiWtCNpBTYmvxO9DPMswa8KSrIc.yKcOJvKbWW4Tq36ZAgwUakZrm8A 6QG7BDboqr5KtH51XhW9CMX9ueOBM6vrV5bQi13cszXLd1QrmS0ybcomeXK8 RmEaOkVB972EXSiTnwFXq1ClOss8JCJq1OgV1OHfrs57McmeOxYWIVvAUc.k b Received: from [71.218.252.178] by web125603.mail.ne1.yahoo.com via HTTP; Wed, 23 May 2012 05:48:54 PDT X-Mailer: YahooMailWebService/0.8.118.349524 References: X-Original-Message-ID: <1337777334.83742.YahooMailNeo@web125603.mail.ne1.yahoo.com> X-Original-Date: Wed, 23 May 2012 05:48:54 -0700 (PDT) From: Gary Casey Reply-To: Gary Casey Subject: Re: 360 still surging X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="933233344-1630952063-1337777334=:83742" --933233344-1630952063-1337777334=:83742 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Ralf,=0AI've read lots of well-meaning, but not always "on point" suggestio= ns posted:=0A1. =A0I don't see this as a serious safety-of-flight issue, al= though your case seems to be more pronounced than normal. =A0This type of s= urging is common (okay, "common" might be a strong word) with all fuel-inje= cted Lycoming engines. =A0They have no fuel return line, so any fuel vapor = that develops has to go through the system into the engine, causing surging= as each bubble passes. =A0The key condition is that it goes away as soon a= s full power is applied. =A0If it also goes away, as mine does, at runup po= wer (about 1800 rpm) I would call it perfectly normal. =A0However, it is no= t normal to surge during taxi right after landing. =A0So, it would still be= good to find the cause.=0A2. =A0The fuel system is almost totally differen= t (refer to no. 6 below) than on a Continental engine, so most fuel system = problems are different in cause and cure. =A0For example, there is no "low"= and "high" pump speeds and if turning on the pump cures the problem (there= should be no difference in fuel flow with the pump on) the problem is upst= ream of the servo. =A0You said there was no change, so the condition is cau= sed downstream of the servo.=0A3. =A0=A0Sorry you went to the trouble and c= ost to get the servo overhauled - that would be very, very unlikely to be t= he cause. =A0There is nothing in the servo that could cause this particular= symptom.=0A4 =A0An intake air leak in a fuel-injected engine couldn't caus= e this symptom - it would just increase idle speed and lean the idle mixtur= e, and most "normal" leaks wouldn't even cause a detectible change.=0A5. = =A0It looks like you have already insulated all the firewall-forward fuel l= ines. =A0The most important is the line from the servo to the distributor, = but that is the one line I most often see neglected. =A0There is no real re= ason to insulate the actual injector lines - they cool off very quickly fro= m the cooling air flow, so they won't be the cause of surging during taxi a= fter flight.=0A6. =A0A fuel line leak that could be sucking air into the sy= stem will most likely cause surging during flight when the fuel flow is hig= h, not during idle conditions on the ground. =A0So while it is remotely pos= sible that it could be an issue, I very much doubt it.=0A7. =A0There is one= element in common with the Continental fuel system and there was one previ= ously posted suggestion that makes sense - the fuel distributor valve may b= e sticking open. =A0The round gizmo on top of the engine might look like it= is merely a way to distribute the fuel to the injectors, but it is a rathe= r delicate component with moving parts. =A0There is a rubber diaphragm to w= hich fuel pressure from the servo is applied and a spring on top pushing ag= ainst that pressure. =A0A piston is attached, and as the pressure increases= the piston gradually uncovers slots in the bore. =A0Each slot feeds fuel t= o a single injector. =A0This valve has a purpose: =A0If there is any differ= ence in injectors in length or elevation, the miniscule fuel pressure at id= le could cause some injectors to get no fuel at all. =A0So these slots are = there to equalize fuel flow during ground operations - the injector nozzle = sizes have nothing to do with fuel distribution. =A0As the fuel flow - and pressure - increases the distributor valve opens to the po= int that it goes past the end of the slots so at higher power levels the fu= el flows unimpeded to the nozzles. =A0Thus, during flight the fuel distribu= tion is only dependent on nozzle diameters and the distributor valve has no= effect. =A0A second function of the distributor valve is to maintain a min= imum back pressure in the system upstream and the benefit of this is a redu= ction in fuel vaporization. =A0With it stuck open, there is essentially no = pressure in the line from the servo to the distributor and vaporization is = likely at any hot, low fuel flow condtion, exactly what you describe. =A0Th= is remains true after shutdown, and with a little luck(at tight seal) a wor= king distributor valve will reduce hot start problems.=0A=0AIn conclusion, = it sounds like the most likely cause is a distributor valve that is stuck i= n the open position. =A0This will have no consequences at any high power co= ndition, but will have an effect on hot idle. =A0It will also degrade idle = fuel distribution, but depending on the injectors and injector line routing= , you may not have noticed. =A0A fuel distributor is something you can disa= ssemble yourself, usually without removal from the engine. =A0Remove the sc= rews on top and the cover, diaphragm, spring and valve can be lifted from t= he assembly. =A0The valve should move effortlessly in the bore, and there s= hould be no trace of dirt or contamination. =A0Give it a shot and let us kn= ow the result. =A0And you might find it useful to post the question on the = Lycoming list - there are lots of Lycoming-specific experts monitoring that= list.=0A=0AAn unrelated comment: =A0The vent hole on top of the distributo= r should be periodically inspected for signs of fuel. =A0Any stain should b= e considered serious, as it indicates a diaphragm that is leaking fuel. =A0= If the diaphragm total ruptures fuel will spray out the vent on top of the = engine and the valve could close, interrupting fuel flow to the engine. =A0= All that could cause a power interruption during flight. =A0This potential = problem is common to both Continental and Lycoming engines. =A0However, I h= ave never heard of one failing in that mode. =A0Still, inspect it.=0A=0AAs = usual, all this is just my opinion, be it ever so humble - or not :-)=0AGar= y Casey=0A=0A=0ADear subscribers,=0A>=A0=0A>When my starter died last month= away from home the local aircraft mechanic convinced me to put a sky-tec s= tarter C24ST5 in my 4P. His arguments were availability reduced weight and = state of the art design.=0A>=A0=0A>It had an external solenoid on it which = interfered initially with my AC-compressor. But it has flange that can be r= otated and I was able to fit it in (but it required a longer power cable fr= om my solenoid plate).=0A>=A0=0A>When I put it on the first time the locati= ng diameter fit felt kind of sloppy to me and the sealing O-ring looked ver= y tiny. After I was home I noticed an oil leak (no drops on the ground but = I can see that the engine looked wet on the rear side).=0A>=A0=0A>I pulled = this starter twice now (a lot of fun!) and the last time I even put very th= in film of gasket maker on the sealing diameter and on the flange ( I reall= y made sure that all surfaces are clean and without damage). I still have a= n oil leak!!!=0A>=A0=0A>Question: is anybody using this sky-tec-starter? Wh= at experience do you have with it?=0A>=A0=0A>It seems to me that the locati= ng diameter is a too sloppy fit and this o-ring on the locating diameter lo= oks really tiny. Since the flange can be rotated on the starter the flange = cannot be used as a sealing surface anymore. Once the oil passes the o-ring= there is nothing that stops it.=0A>=A0=0A>I am thinking about buying the o= riginal starter again.=0A>=A0=0A>Thanks for your input=0A>=A0=0A>Ralf --933233344-1630952063-1337777334=:83742 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Ralf,
I've read lots of well-meaning, but not always "on point" suggestions pos= ted:
1.  I don't see this as a serious safety-of-flight issu= e, although your case seems to be more pronounced than normal.  This t= ype of surging is common (okay, "common" might be a strong word) with all f= uel-injected Lycoming engines.  They have no fuel return line, so any = fuel vapor that develops has to go through the system into the engine, caus= ing surging as each bubble passes.  The key condition is that it goes = away as soon as full power is applied.  If it also goes away, as mine = does, at runup power (about 1800 rpm) I would call it perfectly normal. &nb= sp;However, it is not normal to surge during taxi right after landing. &nbs= p;So, it would still be good to find the cause.
2.  The fuel system is almost totally different (refer to no. 6 below) than on a C= ontinental engine, so most fuel system problems are different in cause and = cure.  For example, there is no "low" and "high" pump speeds and if tu= rning on the pump cures the problem (there should be no difference in fuel = flow with the pump on) the problem is upstream of the servo.  You said= there was no change, so the condition is caused downstream of the servo.
3.   Sorry you went to the trouble and cost to get the s= ervo overhauled - that would be very, very unlikely to be the cause.  = There is nothing in the servo that could cause this particular symptom.
4  An intake air leak in a fuel-injected engine couldn't cause = this symptom - it would just increase idle speed and lean the idle mixture,= and most "normal" leaks wouldn't even cause a detectible change.
5.  It looks like you have already insulated all the firewall-forward fuel lines.  The most important is the line from the= servo to the distributor, but that is the one line I most often see neglec= ted.  There is no real reason to insulate the actual injector lines - = they cool off very quickly from the cooling air flow, so they won't be the = cause of surging during taxi after flight.
6.  A fuel line l= eak that could be sucking air into the system will most likely cause surgin= g during flight when the fuel flow is high, not during idle conditions on t= he ground.  So while it is remotely possible that it could be an issue= , I very much doubt it.
7.  There is one element in common w= ith the Continental fuel system and there was one previously posted suggest= ion that makes sense - the fuel distributor valve may be sticking open. &nb= sp;The round gizmo on top of the engine might look like it is merely a way = to distribute the fuel to the injectors, but it is a rather delicate component with moving parts.  There is a rubber diaphragm to which fu= el pressure from the servo is applied and a spring on top pushing against t= hat pressure.  A piston is attached, and as the pressure increases the= piston gradually uncovers slots in the bore.  Each slot feeds fuel to= a single injector.  This valve has a purpose:  If there is any d= ifference in injectors in length or elevation, the miniscule fuel pressure = at idle could cause some injectors to get no fuel at all.  So these sl= ots are there to equalize fuel flow during ground operations - the injector= nozzle sizes have nothing to do with fuel distribution.  As the fuel = flow - and pressure - increases the distributor valve opens to the point th= at it goes past the end of the slots so at higher power levels the fuel flo= ws unimpeded to the nozzles.  Thus, during flight the fuel distributio= n is only dependent on nozzle diameters and the distributor valve has no effect.  A second function of the distributor valve is to main= tain a minimum back pressure in the system upstream and the benefit of this= is a reduction in fuel vaporization.  With it stuck open, there is es= sentially no pressure in the line from the servo to the distributor and vap= orization is likely at any hot, low fuel flow condtion, exactly what you de= scribe.  This remains true after shutdown, and with a little luck(at t= ight seal) a working distributor valve will reduce hot start problems.

In conclusion, it sounds like the most likely cause is= a distributor valve that is stuck in the open position.  This will ha= ve no consequences at any high power condition, but will have an effect on = hot idle.  It will also degrade idle fuel distribution, but depending = on the injectors and injector line routing, you may not have noticed.  = ;A fuel distributor is something you can disassemble yourself, usually without removal from the engine.  Remove the screws on top an= d the cover, diaphragm, spring and valve can be lifted from the assembly. &= nbsp;The valve should move effortlessly in the bore, and there should be no= trace of dirt or contamination.  Give it a shot and let us know the r= esult.  And you might find it useful to post the question on the Lycom= ing list - there are lots of Lycoming-specific experts monitoring that list= .

An unrelated comment:  The vent hole on top= of the distributor should be periodically inspected for signs of fuel. &nb= sp;Any stain should be considered serious, as it indicates a diaphragm that= is leaking fuel.  If the diaphragm total ruptures fuel will spray out= the vent on top of the engine and the valve could close, interrupting fuel= flow to the engine.  All that could cause a power interruption during= flight.  This potential problem is common to both Continental and Lycoming engines.  However, I have never heard of one failing in = that mode.  Still, inspect it.

As usual, all = this is just my opinion, be it ever so humble - or not :-)
Gary C= asey


=
Dear subscribers,<= /div>
 
When my starter died last month away from= home the local aircraft mechanic convinced me to put a sky-tec starter C24= ST5 in my 4P. His arguments were availability reduced weight and state of t= he art design.
 
It had an extern= al solenoid on it which interfered initially with my AC-compressor. But it = has flange that can be rotated and I was able to fit it in (but it required= a longer power cable from my solenoid plate).
 
When I put it on the first time the locating diameter fit felt= kind of sloppy to me and the sealing O-ring looked very tiny. After I was = home I noticed an oil leak (no drops on the ground but I can see that the engine looked wet on the rear side).
 
I pulled this starter twice now (a lot of fun!) and the last time I eve= n put very thin film of gasket maker on the sealing diameter and on the fla= nge ( I really made sure that all surfaces are clean and without damage). I= still have an oil leak!!!
 
Question: i= s anybody using this sky-tec-starter? What experience do you have with it?<= /div>
 
It seems to me that the locating d= iameter is a too sloppy fit and this o-ring on the locating diameter looks really tiny. Since the flange can be rotated on the starter the flange can= not be used as a sealing surface anymore. Once the oil passes the o-ring th= ere is nothing that stops it.
 
I am= thinking about buying the original starter again.
 
Thanks for your input
 
Ralf
--933233344-1630952063-1337777334=:83742--