REFLECTOR: Engine backfiring

Wed Aug 16 12:21:19 CDT 2006

I thought it was called a sniffle valve.  Mine is homemade from an AN 
fitting.

Dave Scharfenberg

On Aug 16, 2006, at 9:42 AM, Scott Derrick wrote:

>  I thought it was called a whiffle valve?
>
>  Dave Dent wrote:Your right I have seen this before.  Some call it the 
> riffle valve. Manifold
>> drain valve.  I have encountered this valve missing and one time 
>> causing a
>> fire.  The fuel didn't drain out and it back fired and lit off.
>> Good Call Andy
>> Dave
>> ----- Original Message -----
>> From: "Andrew Ellzey" <ajlz72756 at yahoo.com>
>> To: <velocity at davebiz.com>; "Velocity Aircraft Owners and Builders 
>> list"
>> <reflector at tvbf.org>
>> Sent: Tuesday, August 15, 2006 9:44 PM
>> Subject: Re: REFLECTOR: Engine backfiring
>>
>>
>>
>>> Dave,
>>>
>>> I had a Mooney M20E that had this engine and flew it for 15 years and
>>> about
>>> 600 hours. This engine is known for this problem. The first thing I 
>>> would
>>> look at is; there is a 45 degree AN fitting on the bottom of your 
>>> engine
>>> that is supposed to be your airbox drain. This 45 degree fitting is
>>> supposed
>>> to have a check valve internal to this fitting. You would never know 
>>> it is
>>> installed unless you know that it is there. This is the problem, most
>>> people
>>> think it is a standard AN fitting and will install a new fitting 
>>> without
>>> the
>>> check valve at overhaul. With the check valve missing your engine 
>>> sees
>>> this
>>> as an air induction leak and will idle rough and make the backfiring
>>> worse.
>>> A easy way to tell if your valve is working properly is to put your 
>>> finger
>>> over the drain line with the engine running and see if you engine 
>>> lowers
>>> its
>>> idle speed. I have also seen these check valves stuck open and just 
>>> needs
>>> cleaning. I tried to order a new check valve when I found that mine 
>>> had
>>> been
>>> changed out to a standard fitting after fighting this problem for 8 
>>> years.
>>> I
>>> never could get a good part number to order one and had to make my 
>>> own. If
>>> yours is missing or gone bad I can tell you how to make one. Or you 
>>> can
>>> install a PVC valve inline with your drain and it will work just as 
>>> well.
>>> The PVC valve should close as your engine sucks air out of your 
>>> airbox.
>>> This
>>> valve was supposed to drain the excess fuel that drains out of you
>>> injectors
>>> and into your airbox when you shut down your engine and suck closed 
>>> when
>>> you
>>> start your engine.
>>>
>>> Andy Ellzey
>>>
>>>
>>> ----- Original Message -----
>>> From: "Dave Philipsen" <velocity at davebiz.com>
>>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>>> Sent: Tuesday, August 15, 2006 10:38 PM
>>> Subject: REFLECTOR: Engine backfiring
>>>
>>>
>>>
>>>> Here's a question perhaps for some of the engine experts:  I've got 
>>>> a
>>>> STD FG with IO360-A1A engine.
>>>> It has one standard magneto and one Jeff Rose electronic ignition.  
>>>> The
>>>> engine and oil cooling are not a
>>>> problem even with OATs in the low 90s. But, I have a problem (it's 
>>>> not a
>>>> huge problem) with backfiring
>>>> during taxi *after* I land.  Taxiing before takeoff seems to be ok. 
>>>>  The
>>>> backfiring happens maybe once
>>>> every 30 seconds or so.  The engine also seems to run a little 
>>>> rough at
>>>> this time.  I've tried running lean,
>>>> running rich, running on just the magneto, running on just the
>>>> electronic ignition.  None of these seems to
>>>> prevent the backfiring during taxi.  The engine never seems to have
>>>> problems before or during takeoff or
>>>> during cruise or descent...just taxiing back after landing.
>>>>
>>>> I'm starting to think it's a vapor lock problem or something since 
>>>> the
>>>> fuel flow is way down and the fuel is
>>>> sitting in the lines longer and heating up.  I had the cowling off 
>>>> the
>>>> other day and was checking the routing
>>>> of the fuel injector lines and they don't appear to be routed near 
>>>> the
>>>> exhaust manifolds or anything like that.
>>>> I was thinking of maybe experimenting with some insulating material
>>>> around the individual injector lines as
>>>> well as the main fuel line.  Any ideas?
>>>>
>>>> -- 
>>>> Dave Philipsen
>>>> STDFG
>>>> N171SP
>>>>
>>>>
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>>
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>>
>
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>
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