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  #1  
Old 05-19-2018, 02:28 PM
ArlingtonRV ArlingtonRV is offline
 
Join Date: Feb 2005
Location: Marysville, WA
Posts: 574
Default Think I Got a Bad Fuel Pump - Nope I was Wrong

I bought a new mechanical fuel pump (new Lycoming part, hi pressure for injected engine) from Aircraft Spruce last week. While swapping the fittings with the old pump I found that the actuating arm doesn?t move, at all. I know it isn?t supposed to move much, but I would think that some movement is necessary. The old one moves maybe a little more than a quarter inch or so, but the new one, nothing.

Naturally, I will be on the phone with Aircraft Spruce Monday morning, but I was wondering if anyone else has ever seen this. I?ve been in the aircraft repair business (military and commercial) long enough to know that just because a part is new doesn?t mean it isn?t bad but, you know, why me?

Thanks
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Last edited by ArlingtonRV : 05-21-2018 at 11:34 AM.
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  #2  
Old 05-19-2018, 05:29 PM
tim2542 tim2542 is offline
 
Join Date: Aug 2009
Location: Redding,Ca
Posts: 633
Default

I doubt you could move that arm by hand, the spring is pretty stiff.
Tim Andres
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  #3  
Old 05-19-2018, 06:12 PM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
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Default

Good video on aircraft fuel pumps at:

https://www.youtube.com/watch?v=_BfwuUjh_lA

Spring is very stiff, doesn't move much and is hard to move manually.
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  #4  
Old 05-19-2018, 07:37 PM
ArlingtonRV ArlingtonRV is offline
 
Join Date: Feb 2005
Location: Marysville, WA
Posts: 574
Default

I know it doesn't move very much and I would be willing to accept that it can't be moved by hand, except that the one I removed can be. It was working just fine, the only problem appears to be a deteriorating fuel side diaphragm that spits fuel overboard when the boost pump is on.

On the other hand, if the new pump is the way it is supposed to be, I'm good with that too.
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ArlingtonRV on YouTube
RV-8 (Bought Flying)
Glasair Sportsman (Sold)
RV-8 Tail, QB Fuselage (Sold)
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  #5  
Old 05-21-2018, 11:37 AM
ArlingtonRV ArlingtonRV is offline
 
Join Date: Feb 2005
Location: Marysville, WA
Posts: 574
Default Just Like It Is Supposed to Be

I went straight to the top and sent a message to Lycoming Tech. Support and got a response pretty quickly. The tech guy assured me that it was supposed to be this way. Good to know.

I just keep getting hung by the difference between the old one and the new one. I suppose that small amount of play in the old one is attributable to wear, though it was only on the engine for 12 years and about 1,500 hours.

Now all that is left to do is install it.
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Arlington, WA
ArlingtonRV on YouTube
RV-8 (Bought Flying)
Glasair Sportsman (Sold)
RV-8 Tail, QB Fuselage (Sold)
RV-4 (Bought Flying) (Sold)
RV-9 Tail
RV-12 120018 Flying (Sold)
RV-7 Tail, Wings, Started Fuse (Sold)
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  #6  
Old 05-30-2018, 12:30 AM
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RV7A Flyer RV7A Flyer is offline
 
Join Date: Jul 2013
Location: US
Posts: 2,528
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So I just read your blog on the supposed fuel pump issue, and the other threads about it. If I'm reading your blog correctly, the fuel pump was NOT failing.

You should have posted the *real* reason for the fuel leak/blue stain that started you on this venture...per your blog, it was a maintenance-induced failure of the *gascolator* (cut o-ring during cleaning/reassembly), and not the fuel pump at all.

I'm not bashing you, but several threads about the fuel pump supposedly failing might lead others to a similar faulty conclusion, rather than the actual cause...an expensive and time-consuming non-solution to the problem (along with the potential for further maintenance-induced failures during removal and replacement of a perfectly good pump).
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