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05-12-2012, 01:43 PM
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Join Date: Mar 2005
Posts: 4
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Difficult cold start on AFP fuel injected engine
I always thought that fuel injected engines had a difficult warm start behavior, but on my engine that is child's play compared to the cold start behavior. So I suspect I have some kind of an engine problem but I don't know what an I need some help.
I've got a rebuilt Barrett IO-540 with AFP fuel injection, 9:1 pistons, left Bendix magneto and right Electroair electronic ignition. I've studied and used AFP's recommended start procedure. It will not ignite. After a while (about three times ten seconds) I normally get anxious that I have flooded the engine and do an "flooded engine start" with full throttle. In this mode I've managed to get it started every time.
When it is finally started, the warm up RPM is not stable (at 1200 rpm and below). At mag check RPM (1800) it is fairly stable and in flight i notice no issues. The unstable RPM may be worse when returning from a flight when the engine is hot.
The RPM is unstable on both ignitions alone as well as both together. So it seems not to be related to ignition problems.
After start (cold engine) I see a fuel flow of about 6 gph and a fuel pressure of 20 psi (at 1000 rpm). Is that OK?
Also worth mentioning is that I have not installed the AFP purge valve, or to be precise, it is installed but plugged and inoperable - and leak free.
Any advise what to check for is greatly appreciated.
Lorenz.
RV-10 #40280
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05-12-2012, 02:42 PM
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Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,393
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engine
How much time on the engine? They tend to run a bit ragged the first few hours.
Has the idle mixture been properly adjusted?
I ALWAYS leaned immediately after start on the injected engines, whether an Aztec, Pitts or whatever.
A stable mid gage fuel flow reading for cold start is more reliable than timing. You just have to experiment and find what your engine likes.
What is the ambient temp. my experience is that all these engines run a little ragged at low r/m
. They are worse in hot weather and the straight exhaust is rougher than the crossover.
If none of this works check the induction tubes including removing the induction elbows-check for flatness and install new gaskets.
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05-12-2012, 04:01 PM
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Join Date: Nov 2007
Location: Mississippi
Posts: 282
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So,.. exactly what are you doing.... and what have you tried?
Have you tried less time on the booster before cranking? Changed any setting on the throttle or mixture?
I found I really needed less time on booster than recommended. (have a different system than you do)
p.s. might check the recommendations on the starter,... believe most recommend you not run them 10sec at a time
__________________
Wallace & Marietta Goodloe
9A -QB
N211LV
Phase 2 has started! 
Thanksgiving time, is dues time for us
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05-12-2012, 04:12 PM
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Join Date: Nov 2005
Posts: 121
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Rich?
In the airplane that I fly, I usually only see 2-3 GPH at 1000 RPM. This is a 300 hp Continental... but 6gph sounds high. Perhaps your to rich, which would cause rough idling and hard starting. That would explain why the flooded starting technique works for you.
-David
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05-12-2012, 04:34 PM
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Join Date: May 2010
Location: Denver
Posts: 564
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[quote=
I've got a rebuilt Barrett IO-540 with AFP fuel injection, 9:1 pistons, left Bendix magneto and right Electroair electronic ignition. I've studied and used AFP's recommended start procedure. It will not ignite. After a while (about three times ten seconds) I normally get anxious that I have flooded the engine and do an "flooded engine start" with full throttle. In this mode I've managed to get it started every time.
When it is finally started, the warm up RPM is not stable (at 1200 rpm and below). At mag check RPM (1800) it is fairly stable and in flight i notice no issues. The unstable RPM may be worse when returning from a flight when the engine is hot.
The RPM is unstable on both ignitions alone as well as both together. So it seems not to be related to ignition problems.
Lorenz.
RV-10 #40280[/QUOTE]
Lorenz,
I have the same Barrett engine with AFP injection and 9.0 pistons, with 2 Bendix Mags and purge valve. After 30 secs. purge, my cold start procedure is mixture full rich, throttle 1/2, fuel boost 5 secs. then ignition. Always starts within 2-3 blades and runs smooth immediately. In 2 years I have never had to do a flooded start. Hot starts are a non-issue with the purge valve. I recommend you hook it up; although it will not help your current issue. I will check my fuel flow & pressure at idle when I fly tomorrow.
I will leave it to the engine gurus to offer solutions, but will tell you that it is not normal/usual for this engine to run ragged/rough when new or cold.
Jim Berry
RV-10
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05-12-2012, 05:22 PM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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The RV-8 I fly requires no more than 1 second (yes, one second) of prime or it is too fat at start. My Hiperbipe needs the "logical" 3-5 seconds. Same injection system, but different boost pumps.
Forget the books and figure out what your system needs. If you are too fat, reduce the prime - if too lean... well, you know.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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05-12-2012, 10:53 PM
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Join Date: Oct 2005
Posts: 1,516
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Cold start is a none issue
Jim Berry is right on.
My set up is the same as yours, although 8:1 compression.
Cold starts are a one revolution event and have been on this engine, 75hrs since new and 450 hours on the same set up in an RV8 IO-360.
There is no need to purge a cold engine and my throttle is barely cracked open so as not to exceed 1000 RPMs on start up. A few seconds of running and I lean the mixture to the max and the engine runs smooth as a sewing machine. I give it a few seconds (3to5) of boost (prime) for cold start.
I don't know the history of your plane or engine installation but the fact that your purge valve is not hooked up tells me someone was in a hurry to finish
the installation. This leads me to believe that certain final adjustments to the
idle mixture control and perhaps even magneto and electronic ignition timing adjustments have not been made.
Give us a little more info an someone will be able to pin point your starting problem. You can expect your set up to be absolutely trouble free when all adjustments are done correctly.
__________________
Ernst Freitag
RV-8 finished (sold)
RV-10 Flyer 600 plus hours
Running on E10 mogas
Don't believe everything you know.
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05-13-2012, 03:48 AM
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Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,271
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With ernst on this.
This is THE cold start procedure for an IO540
WOT, FULL RICH
Boost pump, on and as soon as the pressure gets to 20PSI or more count "One Thousand Two Thousand" and pump off.
Mixture ICO.
Throttle cracked enough to give you 1200 RPM.
Crank!
Hot start, Do nothing! Crack throttle the same, crank, as soon as it coughs, run the mixture up.
AFTER START - BOTH CASES
Lean until the RPM peaks, then ever so slightly starts to fall again. Taxi like this.
Runups done same setting at 1700 or so RPM, and richen ONLY enough to keep it smooth, no more. Watch EGT's all rise on each mag, if they dont, and one falls, you will know which plug! Cycle the prop ONCE!!
Return mixture to the leanest possible again before lining up.
Line up procedure....Pump on, Mixture rich......ROLL!
If your procedures are not like this, change!
This does EVERYTHING it should.....And NOTHING it shouldn't! 
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05-13-2012, 07:10 AM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
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Just to add my 2c -
I have found that with the idle mixture properly adjusted, on a properly operating FI system, that leaning at low RPM/taxi/run-up is not required.
I agree with leaning on the ground with a carb, that's a different animal.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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05-13-2012, 09:45 AM
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Join Date: Feb 2008
Location: Largo, FL
Posts: 1,029
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Just something I found
When our IO540 would not start easily, hot or cold, we found we had a retard breaker magneto on the left (starting) side (no impulse coupling). It did not have a "shower of sparks" box hooked to it, therefore, not giving the necessary spark for easy starting. We hooked a Slickstart to it and the problem went away.
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