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Before the fuel pump exchange - one last question
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philperry9



Joined: 23 Nov 2011
Posts: 379

PostPosted: Mon Aug 14, 2017 11:22 am    Post subject: Before the fuel pump exchange - one last question Reply with quote

Couple of small items to report, but no smoking guns yet.  Just a couple of small items.  But for the benefit of the group or those coming after me in the archives...

1) The system from the left tank to the firewall is tight.
2) I learned that it doesn't take much vacuum (5 inches is enough) to leak fuel from the right side of the Andair fuel valve to the left.   Not surprising as the valve is designed to operate near-zero pressures and just provide the path of least resistance.   So the valve is a bit difficult to test if you're looking at doing it with vacuum.  Lessons learned.
3) I did replace the line from the fuel valve to the filter.  It passed the leak test, but did show signs of stress on the flares.  So I went ahead and replaced it.
4) The thing I did find that could potentially be a clue came when checking the fuel strainer on the right tank.  The strainer was clean and I was getting ready to re-install it when I noticed this nick where the flare fitting would seat.  It looks more like an abrasion with a file than a nick.  Photos attached.  If you look closely, you can see where the flare would seat on the fitting and a small portion of the abrasion intersects that "ring".   This fitting hasn't leaked fuel, so there's no promises here.  But it's marginal enough in quality that I want to replace it so I don't have to worry about it being a cause going forward.  It's possible that it was leaking just enough air to put a bubble up at the sensor.
Who knows....  But I called Vans and ordered a replacement overnight.    
I'm done until it shows up.   I've got things torn down enough at this point that I don't want to complicate things any more by proceeding to check other items.  Just want to finish up what I've started, get it back to a known state, then proceed from there with further inspections.

But thats the info at this point.

Phil
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On Sun, Aug 13, 2017 at 10:36 AM, Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)> wrote:
Quote:
Thanks for all the ideas.   I'm willing to entertain all of them.

I am working through the stuff under the seats right now, just to 100% rule it out and drive a stake any issues or doubt lingering under there.

Aside from checking screens and strainers, I'm pulling a vacuum on each segment of the fuel system and watching for a leak down on the gauge to be 100% confident there are absolutely no air leaks.  At that point I can feel 100% certain all my efforts need to be focused forward if the firewall.

I hate breaking apart the system to investigate because it introduces more variables.   But systematically going through the thing and putting and eyeball and wrench on everything is the only way to clear them 100%.

What I can tell you definitively right now.

1) There is no air leak in the fuel line segment between the boost pump and engine drive pump inlet.

2) The fuel filter is clear, minus a couple of small little fibers tucked into the bottom corner of one pleat.   It's was good.

3) The finger strainer in the left tank is clear as the day it was installed.

Everything beyond that is speculation right now.   I will continue to run out the lines on the left side after church.  Then I'll move on to the right.

After vacuum testing is competed to prove no-air, I will flow test with fuel from both tanks going forward.

Then, once that's done, I'm 100% focused forward of the firewall.

At this point, the only way to get hard answers is systematically work through it piece by piece.

I'll keep you posted.

Phil







Sent from my iPhone

> On Aug 13, 2017, at 10:00 AM, Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:
>
> --> RV10-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>
>
> IMHO, doing anything with the injectors at this point would be a waste of time and wear an tear on the injector lines. Anything in an injector will cause a steady state lean condition, easily observable on EGT as higher than normal. Roughness indicates a variable condition, such as inconsistent spark, air/water in fuel, etc. Roughness after a hot start is normal for a few minutes, due to vaporized fuel in lines.
> I suppose a small item in an injector could move around, but not too common. Also, since I know Phil has quick build wings, any debris left in tanks would be minimal, should be caught by screens and filter in system.
> Kelly
>
>> On 8/13/2017 7:49 AM, bill.peyton wrote:
>> --> RV10-List message posted by: "bill.peyton" <peyton.b(at)sbcglobal.net (peyton.b(at)sbcglobal.net)>
>> Just an observation after reading this thread.  I am not convinced that the pressure fluctuation and the engine stumble are related.  It would seem that your pressure would have to drop below 15 psi for the engine to react.  With your new pump, you are never seeing pressure that falls below an acceptable pressure for normal ops.  Also, have you checked your fuel vents? Also, pull all your injector restrictions and do a clean and check.  Purge the lines prior to reinstallation
>> Have you looked at your egts? Could it be a shorted or open plug?  Have you done a lean mag test on the ground and does either mag exhibit and stumble more so than the other?
>>  It seems to early for a sticking valve, but could be something has gotten under the seat of an intake valve which might account for the stain in the fab
>> --------
>> Bill
>> WA0SYV
>> Aviation Partners, LLC
>> Read this topic online here:
>> http://forums.matronics.com/viewtopic.php?p=471816#471816
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