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  #1  
Old 04-21-2020, 04:09 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,439
Default Oil from Fuel Pump Overflow

For some time now, I've been parking the airplane and coming back a few days later to find a spot of oil under the aft edge of the cowl. We're talking a half ounce of oil, maybe less - a very small amount. During flight, there are/were no apparent leaks (no oil on the belly) and I haven't had to add oil to the airplane. I've looked for the "after shutdown" leak a couple of times with the cowl off, but didn't identify the source until today.

It looks like the oil is coming out of the overflow line for the mechanical fuel pump. Is there any explanation other than a faulty diaphragm in the fuel pump?
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2001 RV-6 N46KB
2019(?) RV-10
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  #2  
Old 04-21-2020, 04:21 PM
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DanH DanH is online now
 
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Quote:
Originally Posted by Kyle Boatright View Post

It looks like the oil is coming out of the overflow line for the mechanical fuel pump. Is there any explanation other than a faulty diaphragm in the fuel pump?
Nope.

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  #3  
Old 04-21-2020, 08:07 PM
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airguy airguy is offline
 
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The verdict is as good as your diagnosis - if it's really oil coming out of the fuel pump overflow line, then it's really your fuel pump diaphragm.
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Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #4  
Old 04-21-2020, 09:06 PM
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AlexPeterson AlexPeterson is offline
 
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Kyle, out of curiosity, how old is that fuel pump?

There is a lot of evidence in various threads and posts here that they should be preemptively changed every 5-8 years. Dan H. posted detailed observations on the diaphragm breakdown in a startlingly short time.
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  #5  
Old 04-21-2020, 09:14 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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Quote:
Originally Posted by AlexPeterson View Post
Kyle, out of curiosity, how old is that fuel pump?

There is a lot of evidence in various threads and posts here that they should be preemptively changed every 5-8 years. Dan H. posted detailed observations on the diaphragm breakdown in a startlingly short time.
This one is just over 4 years old. My first one lasted about 15 years.
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  #6  
Old 04-22-2020, 05:26 AM
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Vlad Vlad is offline
 
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Quote:
Originally Posted by Kyle Boatright View Post

.....

Is there any explanation other than a faulty diaphragm in the fuel pump?
Yes. At certain flight regimes the oil from breather swirls corkscrew. Couple drops could be trapped in the camloc by the drain. Could even leave a trace after your next flight. The trace would start from the pump drain.
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  #7  
Old 04-22-2020, 01:41 PM
WingsOnWheels WingsOnWheels is offline
 
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Quote:
Originally Posted by Vlad View Post
Yes. At certain flight regimes the oil from breather swirls corkscrew. Couple drops could be trapped in the camloc by the drain. Could even leave a trace after your next flight. The trace would start from the pump drain.
I used a clear line for the vent, makes it obvious, can see the oil in the line.

I have been in this same boat, time to change the pump.
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