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Date: Sun, 24 Jul 2005 12:55:05 -0500
From: Jim Sower <canarder@frontiernet.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: FUEL FLOW was Re: [FlyRotary] Lycoming debugging
 test - -HELP!
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I changed all my fuel filters.  Water contamination seems impossible 
since the engine feed tube is cheated off the bottom of the sump about 
1/2" and the water drain is flush with the bottom.  My engine was fairly 
stable as far as configuration goes:  Fuel flow installed 6 months prior 
and working well, E-Mag installed more recently (just a few hours) but 
seemed to be working well - mag checks taken on the ground, in flight 
and during the problem indicated all ignition components were normal.

I could entertain the notion that vapor lock or air introduced into the 
system was involved, but I can't come up with a scenario where the 
engine ran great all summer and then acted up on cool days down in the 
fall.  The conditions for vapor lock aren't intermittent to my knowledge 
- not there on a hot day, kicking my ass on a cold day.  My fuel system 
was inspected to a fair-thee-well (except no in-flight fuel pressure).

Kevin - let me know what you find on the Lyc list.  I'm going to call 
Mattituck and talk really extensively to the guru there since mine is a 
Mattituck engine with ~ 600 hrs.

We'll share info and maybe get to the bottom of this quicker ... Jim S.

kevin lane wrote:

> thank you for the reply.  I will start looking into my fuel supply.  I 
> do have a flow meter but haven't been watching it too much since I was 
> so concerned with the very high CHT's that I've been hitting.  the 
> mesh filter in the carb is good, brand new in fact.  I have two auto 
> mesh fuel filters ahead of the facet pump.  they look clean thru the 
> glass, but I will remove them and look more closely.  I have been 
> reluctant to remove the wing tanks in order to check the pick-up tubes 
> since it is so much work, plus my tanks are quite full.  I suppose I 
> could try to back flush them first with an air hose if I am VERY 
> careful.  now that I think about it I don't think I have tried 
> switching tanks yet.  that would certainly be an easy task.
>     I believe that my fuel flow meter was showing 8.5+ gals/hr at full 
> throttle.  now that I think about it that may be low, and 10.5 more 
> typical.
>     thanks for your help.  we are having absolutely beautiful weather 
> here and I was so anxious to do some flying, but....at least I can 
> hang out at the airport some more.  it's nice to find someone who 
> doesn't immediately say "I'd get rid of that electronic ignition to 
> begin with"!
>     to answer Tracy, yes I have EGT's, shows low 1100's since I am 
> running full rich,  I have manifold pressure but never looked at 
> it(I'd make a hell of an experimental test pilot-wait, I am one, 
> oops).  in my defense, I have been nervous running my CHT's up past 
> 400 degrees in order to replicate this problem, since I just had three 
> cylinders welded because of who knows what?  I've been thinking about 
> attaching my leaf blower to my plenum to help cool things on the 
> ground runups.  it produces 220mph wind, or so the box says.
> Kevin Lane  Portland, OR
> e-mail-> n3773@comcast.net <mailto:n3773@comcast.net>
>
>     ----- Original Message -----
>     *From:* Leon Promet <mailto:leonp@pacific.net.au>
>     *To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
>     *Sent:* Saturday, July 23, 2005 2:48 PM
>     *Subject:* [FlyRotary] FUEL FLOW was Re: [FlyRotary] Lycoming
>     debugging test - -HELP!
>
>     Hey Kevin,
>      
>     Check your fuel FLOW RATE,  especially at your normal climb angle 
>     (on the ground).  It sounds like it's losing fuel flow on take-off
>     - the carb is using whatever fuel is in the bowl,  and then
>     running lean. You might have to jack the fuselage to the required
>     angle in case there is something in the tank that is occuding the
>     pick-up(s).  However,  if you can reproduce it on the ground doing
>     a run-up,  it definitely sounds like lack of fuel FLOW (not
>     pressure) to me.  If the engine will maintain 1700 RPM,  then it
>     is getting almost but not quite enough fuel FLOW at WOT.
>      
>     Various things come to mind.  FIrstly,  (and most easily),  a
>     partially blocked fuel filter (just because it's new doesn't mean
>     it'll work!!).  So change that first.  Use a different brand to
>     eliminate faulty batch manufacture. 
>      
>     I once had a mysterious problem with an RX4.  Chased it for
>     weeks.  Turned out to be a bee in the fuel line. (I'm serious -
>     the guy who owned the car used to work for me and is still around
>     and will verify this!!).  Anyway,  Jack's pride & joy would work
>     just fine around town.  But out on the open road,  it would run
>     out of fuel in 3rd gear (usually when overtaking).  Turned out
>     that a bee (very dead at this stage) had got into the fuel
>     tank. (The problem occurred soon after Jack filled up at some
>     outback petrol station when he was on holidays).  The bee
>     immediately got stuck in the fuel supply line.  At normal cruising
>     flow rates,  there was sufficient fuel to run the car. On hard
>     acceleration,  the bee's wings & body would PARTIALLY block the
>     supply line in the tank.  We only found it when we removed the
>     tank,  replaced it with another one,  and cut the old one open. 
>     You just wouldn't read about it in Ripley's or the War Cry!
>      
>     I've also had pieces of fuel gum (and one instance a piece of
>     cardboard) block the fuel pick-up.  When fuel sits a long time at
>     a bowser storage tank,  especially if there is water at the bottom
>     of the tank,  it will form a sheet of gum at the fuel/water
>     interface,  almost like condom latex,  (but nowhere near as
>     strong).  This film of gum gets broken up the next time a tanker
>     does a dump,  and bits of this will very effectively block a fuel
>     pick-up,  or cripple a fuel filter. 
>      
>     I've seen it happen on several occasions over the years.  It was
>     particularly prevalent in the early '70s during the phase out of
>     "standard" petrol before the introduction of unleaded into this
>     country (all rotaries used to run on standard not super - which
>     was heavily leaded back then).  I found out the hard way soon
>     after I had purchsed my RX2 Coupe in 1971. Filled up at an "out of
>     the way" petrol station (where the fuel sales volume on standard
>     was virtually nil),  and immediately had problems.  After
>     eventually getting back to Sydney,  we quickly diagnosed it as a
>     tank problem.  Even steam cleaning the tank didn't fix it.  The
>     tank was replaced,  and we cut open the old one,  and there was
>     all these bits of gum,  just like a thin membrane tyhat had been
>     cut up.
>      
>     So the place I'd be looking is in your fuel SUPPLY system,  as it
>     seems you have done everything else except check fuel FLOW rate. 
>     Can't guarantee that this IS the problem,  but the quick and easy
>     way would be to check your open flow rate at the carb,  and then
>     compare it with somebody else's.  Alternatively,  you can work
>     backwards as you know that the engine requires at least 0.55 Lbs
>     per hour per BHP at WOT. (First convert that to litres or pints or
>     quarts per minute and you can direct measure it,  or run the fuel
>     into a can for 1 minute and then go and weigh it).  Fuel flow rate
>     should be at least 25% more than the max required at WOT so that
>     your carb doesn't run dry.
>      
>     One other area of the problem could be the incorrect needle/seat
>     arrangement on the carb,  or a partially blocked filter at the
>     banjo - I'm not privvy to what carb you are running so this is
>     conjectural as I plead total ignorance of Lycoming carbs. 
>     However,  all stock Mazda carbs have fine brass gauze mesh
>     filters,  both at the banjo,  and on top of the needle& seats.
>      
>     Additionally, in the racing 13Bs,  an IDA Weber would run out of
>     fuel as the float bowl was just way too small for anything over
>     250 BHP.  We used to replace the 2.5 needle/seat assys with 3.0
>     units.  But  we would STILL run out of fuel on long straights. 
>     Extended float bowls were then added,  which did fix the problem, 
>     but welding the Weber material was tricky,  especially if it had
>     been saturated with oil laced fuel for a long time (sometimes the
>     castings were slightly porous)..
>      
>     My final solution was to add an EXTRA float bowl (from an SU
>     carb),  with it's own needle & seat,  and a fuel return.   We
>     could then go back to a 2.5 Weber needle & seat,  as the 3.0 one
>     was prone to flooding at idle and on the over-run. (Nothing good
>     has ever come of fuel dilition of engine oil in a race
>     engine). This fixed all fuel flow issues.  Some time
>     later, affordable aftermarket EFI came along,  and all this passed
>     into history.  But fuel SUPPLY issues are even MORE critical with EFI.
>      
>     So these are just a few areas where you can look.  Be systematic, 
>     and start at the connection between the carb and the supply line. 
>     You will then quickly eliminate either the supply to the carb,  or
>     the carb needle & seat itself.  If the open pipe fuel flow is more
>     than adequate,  then I'd be looking inside the carb for
>     restrictions.  As I have said,  this is only a guide.  Feel free
>     to contact me off line if you feel the need.
>      
>     Cheers,
>      
>     Leon
>      
>      
>     ----- Original Message -----
>
>         *From:* kevin lane <mailto:n3773@comcast.net>
>         *To:* Rotary motors in aircraft
>         <mailto:flyrotary@lancaironline.net>
>         *Sent:* Sunday, July 24, 2005 6:33 AM
>         *Subject:* [FlyRotary] Lycoming debugging test - -HELP!
>
>         I realize that this isn't exactly the right forum, but you
>         guys seem to have excellent debugging skills.  my local RV
>         group is totally worthless ("I find the carnauba wax doesn't
>         show fingerprints as much as the....")(except Mike!)  the
>         on-field mechanics are sick of me coming by.
>             my O-320 RV-6A is having RAG (rpm attention getter)
>         problems.  it runs fine until about 300' on take-off, then the
>         rpm's drop to like 1700 (from 2200).  switching mags to
>         electronic ignition(Rose) makes no difference.  mixture no
>         diff.  pulling the throttle it will seem to run fine at
>         1700rpm.  I have 4 new cyls that I am attempting to break in. 
>         ground run ups can only go like 2 minutes before CHT's exceed
>         400 degrees.  I discovered I can get the rpm drop on the
>         ground if I run it a minute or so full power.  cht's will
>         typically approach 415 degrees when the drop takes place.  I
>         don't know if the temp is significant or not, it does seem
>         that way.  I have a brand new slick left mag.  rose checked
>         the electronic ignition and could find nothing wrong, even put
>         it in an oven to test.  I installed a new carb since the old
>         one showed signs of leakage (and I'm at whits end).  no
>         change.  my fuel pressure has been showing 8psi this last
>         year, up from 6 psi when originally installed.(no idea why)  I
>         installed a pressure regulator in-line which works like a
>         charm.  I can dial whatever pressure I like.  2 psi makes no
>         difference.  I bypassed the mechanical fuel pump and ran it
>         just on the facet electric.  2 psi, no difference. I
>         discovered that you can run the carb for maybe 30 secs with no
>         fuel pressure while it burns off the bowl gas. premier engines
>         suggested induction leak making the engine run lean.  no leaks
>         detected cold or hot engine. (pressurized intake with vacuum,
>         sprayed soapy water)
>             if the engine didn't run right to start with then many
>         explanations would hold.  but it runs fine for several
>         minutes.  it runs the same under mag or electronic ignition
>         both before and after the problem kicks in.  everyone really
>         wants to blame the rose ignition, but I'm not seeing any
>         connection.  with such a quick run-up my oil temp barely
>         registers, so I doubt parts are seizing.  I have new mineral
>         oil in it for breakin right now.  there is a bit of MMO in the
>         fuel too I believe, left over from a mechanics "what the hell"
>         attempt from way back.  my cyls are all new, rebuilts, so no
>         valve problems.  I checked the push rod lengths when I
>         reinstalled them.  the engine isn't missing when the problems
>         occurs, it simply won't run faster and it seems to prefer the
>         throttle pulled back to match the rpm it is putting out.  I
>         can't figure out any more lean mixture scenarios to try.  the
>         new carb runs just like the old one did.  I recently replaced
>         the mag harness with a much newer, used one.  I tested it and
>         it was fine.  the plugs are all new, but again, no diff
>         between mag and elec ignition.  if I flip the ignition to R
>         and shut off the elect ig then the engine quits as would be
>         expected, no wiring problems.
>             fuel, spark, air, timing, that's all there is.  this damn
>         lycoming lawn mower has me stumped.  my engine has been
>         running fine up until this (hey, we all have "cracked"
>         cylinders, get out your microscope and look!).  you guys have
>         any ideas?
>         Kevin Lane  Portland, OR
>         e-mail-> n3773@comcast.net <mailto:n3773@comcast.net>
>
>             ----- Original
>