REFLECTOR: Fuel Filters / Clogged Injectors

[John Tvedte]

Terry,

I believe you are referring to the filter which is an Airflow Performance supplied product.  The Factory may or may not obtain theirs from Airflow - I am not sure.  The one supplied by Airflow - has a SS screen - and is a lifetime filter.  If you have any questions or concerns, I'm sure Don @ Airflow would be happy to address them.

John
________________________________
From: reflector-bounces at tvbf.org [reflector-bounces at tvbf.org] On Behalf Of Terry Miles [terrence_miles at hotmail.com]
Sent: Friday, August 14, 2009 1:53 PM
To: jerry at jlbent.com; 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Fuel Filters / Clogged Injectors

I just did my annual inspection.  The took the gold (factory engine kit) fuel filter out and just back washed it a little.  It seems completely clean.  Does that filter have a service life?  Or a specific periodic maintenance/inspection procedure?
Thanks,
Terry

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of jerry at jlbent.com
Sent: Friday, August 14, 2009 08:07
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Fuel Filters / Clogged Injectors

It is important to understand that even a 40 micron filter (the one that is part of the factory installation kit) did not prevent the clogging of injectors on an IO540.

This is a bit off the filter thread (but related) and even farther off the original thread so I have started a new and more appropriately titled one.

-----------------------

I have been remiss in documenting this so here goes:

We chased this problem for WAY too long.  The engine had been fine and then it started running rough.  All I can figure is that the finer fiberglass particles get through the "stock" filter and then when the engine is shutdown the fuel evaporates and some resin is deposited and carborizes in the bore of the injector.  A few engine runs later, the injector is either completely blocked or blocked enough to cause the other cylinders to be way rich.  If one injector is blocked then an IO540 will run 16.6% rich and that is just about too rich to run.  This happens due to the way fuel is distributed in the injector system.  For any RPM MP setting, the air intake servo sends to the spyder the amount of fuel appropriate for 6 cylinders.  This fuel is then distributed to the injectors according to the flow characteristics of each line and injector combination (this is where GAMI works to balance flow).  So, when one injector is obstructed, the other 5 cylinders will be sharing what doesn't go through the clogged injector.  This can be countered by leaning but the best you can do is a rough engine with less than 83% power.  If you are in the air, find an airport!  Beli! eve that a 5 cylinder IO 540 is not comfortable!

The general evidence for this is 5 cylinders with "wet" (black/sooty) plugs and one that looks fine.  Since one cylinder is going LOP and the rest are going ROP, the temps are not going to be a good diagnostic.

The fix is very simple.  Remove and clean all the injectors.  You will probably find one that is obviously clogged (magnifying glass is a good idea), any or all may be getting worse.  Be careful when reinstalling.  These injectors to distribution lines connectors are easly stripped.  The directions are to bring them to "Finger Tight" and then 1/4 turn more.  This can be a bit tricky.  The distribution line must be properly straight aligned with the injector.  The only way I know to do this is by feel.  When aligned you can screw the cap nut down until the distribution line won't wiggle easily.  That's the magic "Finger Tight".

Many on this sight already know all of this and can correct and expand on the information provided.  I know that this is an insidious problem and can take months to diagnose on a fresh engine installation.  There are so many variable that will provide the same behaviors and with a good filter that look clean, it does not appear to be the problem.  I provide my experience only as a amateur builder, not as a qualified A&P or especially a fuel system expert.  It's all about the learning


Jerry Brainard
N202VB XLRG Building Slowly


-------Original Message-------
From: Dave Philipsen
Subject: Re: REFLECTOR: Fuel Consumption Performance
Sent: Aug 13 '09 5:48pm

HYTEC45 at aol.com wrote:
> In a message dated 8/13/2009 1:55:48 PM Pacific Daylight Time,
> velocity at davebiz.com<http://mbox.jlbent.com/compose.php?to=velocity@davebiz.com> writes:
>
>     The sump/drain acts as a gascolator itself.
>
> True, however the cascolator has a 74 micron screen just in case any
> "floaters" are lurking.
> TEC
>
Good to know.

--
Dave Philipsen
Velocity STD FG
N83DP

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