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11-25-2011, 03:26 PM
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Join Date: Jun 2006
Location: Ottawa, Ontario, Canada
Posts: 2,116
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engine stoppage after startup
Today a few seconds after starting my plane, the engine mysteriously stopped, for no discernable reason. After turning on the fuel pump (I normally start without the fuel pump on) and restarting, everything was fine. All engine instruments reading normal. I taxied arouund for a while, did a runup, no problems. Flight was uneventful.
What could explain this? With almost 100hrs hobbs time, this has never happened. I have a carbeureted o-320 with one elec ign and one mag. The fuel selector was on (left tank) and both tanks had fuel. As I said, after turning on the fuel pump for the second start, the problem did not recur.
One thing I did notice, is later after the flight I was inspecting my left tank vent line and found wet fuel around a vent line fitting on the right tank. I removed the line from the fitting and inspected the flare, which was fine. I did have some fuel dribble out of the vent line when i removed it from the fitting, however. Not sure how it got in there.
Any theories as to what could cause an engine to spontaneously stop just after startup, and then run fine? It had sat for one week, and it was not very cold out, and I did give it a good dose of priming. I started without the boost pump on, but I routinely do this and have never had a problem.
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Phil
RV9A (SB)
Flying since July 2010!
Ottawa, Canada
Last edited by prkaye : 11-25-2011 at 03:36 PM.
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11-25-2011, 04:10 PM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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You said no boost pump on start, but how about before? Did you run it to at least fill the float bowl?
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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
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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11-25-2011, 04:34 PM
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Join Date: Jun 2006
Location: Ottawa, Ontario, Canada
Posts: 2,116
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yes I ran the boost pump, primed it for 4 or 5 seconds, and then stopped the boost pump and then started.
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Phil
RV9A (SB)
Flying since July 2010!
Ottawa, Canada
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11-25-2011, 04:40 PM
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Join Date: Dec 2005
Location: Andernos les Bains, France
Posts: 244
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Water?
How were your samples from tanks purge?
Might be some water from condensation if your tanks were not full during that last week.
I hate intermittent problems like that. They keep you wondering what happened and if it could happen again.
Good luck in you quest.
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Daniel Mouly
VAF #778 - [2013 payment done]
RV-9A Emp. & Wings 95%, Fuse 70%
Austin Healey 3000 MKIII fully restored
LFCD (Andernos Les Bains), France
Construction Log comments in French (not really up to date, sorry)
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11-25-2011, 04:51 PM
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Join Date: Nov 2006
Location: Boise, ID
Posts: 1,095
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Mine does this in cold weather, and from what I've been told, auto-fuel is the reason. No clue if that's the reason or not...doesn't make sense, but I've read it somewhere, too. I have to let the engine run at idle to warm up for 30 seconds to a minute before I advance the throttle. If I give it more than about 1,000 RPMs prior to that it'll just stop. Is that what you're experiencing?
Edit: Just to clarify, I'm using 93 Octane no-ethanol fuel. My fuel samples are clean and water free, too.
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Sonny W
Boise, Idaho
RV-7A Flying!
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11-25-2011, 04:56 PM
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Join Date: Jun 2006
Location: Ottawa, Ontario, Canada
Posts: 2,116
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Weird... I am using Shell V-Power: 91 Octane no ethanol auto gas. I started using this fuel this summer. Today was probably the coolest day I've run the plane on this fuel, but it was still above freezing.
Interesting... I wonder why the cold weather would cause this on auto fuel? if this turns out to be the cause, I guess I should switch to avgas for the winter.
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Phil
RV9A (SB)
Flying since July 2010!
Ottawa, Canada
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11-25-2011, 05:15 PM
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Join Date: Dec 2008
Location: Big Sandy, WY
Posts: 2,567
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Were you full rich or ICO when you boost primed? Carb bowl was probably not full. The only really bad possibility I can think of would be a needle valve struck momentarily.
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Actual repeat offender.
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11-25-2011, 05:28 PM
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Join Date: Jun 2006
Location: Ottawa, Ontario, Canada
Posts: 2,116
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full rich during priming.
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Phil
RV9A (SB)
Flying since July 2010!
Ottawa, Canada
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11-25-2011, 05:30 PM
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Join Date: Dec 2008
Location: Big Sandy, WY
Posts: 2,567
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Duh...make that float valve, not needle valve. Musta cramped a gray lobe.
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Actual repeat offender.
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11-25-2011, 06:04 PM
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Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,574
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probably just cold engine
It is very likely that the mixture was just not quite rich enough for a cold engine.
Without any kind of choke, running on cold auto gas with a cold engine is difficult - hard to get the fuel to stay suspended and start vaporizing in the intake manifold, rather than condense on the walls.
The switch from summer gas to winter gas changes the low-temperature volatility to try to help this, but you may still have summer gas in your tank.
My bet is that it would have started again and run fine, even without the boost pump on.
Even my F.I. engine will, once in a while on a cold morning, start then die in 10-15 seconds or so if I let the rpm get too low. Then, it starts right up afterward and runs fine.
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Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 625
LS6-15/18W sailplane SOLD
bought my old LS6-A back!! 
VAF donation Jan 2020
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