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  #1  
Old 10-20-2013, 03:06 PM
rleffler's Avatar
rleffler rleffler is offline
 
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Location: Delaware, OH (KDLZ)
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Default Fuel Pump Issue

As several already are aware, I had some fuel flow issues on my first flight. At the time, in the air, I wasn?t quite sure what the issue may have been. It was initially looking like a blocked fuel line. The symptom was that the fuel pressure dropped significantly, but came back up with the electric fuel pump turned on and switching the tanks. I promptly landed and started looking for the root cause.

1. The left and right tank fuel flow (measured at the firewall, forward of the filter and pump) was 58 gallons/hour. Rules out a blockage aft of the firewall.
2. The fuel vents are not obstructed

I ran the engine in a static test. Was getting about 20psi on the engine fuel pump and about 26psi with the electric fuel pump enabled. Since this is all within specifications, this is the worst of all the scenarios. No root cause and everything seems to be working as designed.

This morning I flew for about an hour on flight #2.

When I turned off the electric fuel pump, fuel pressure started to immediately drop. I let it drop to about 10psi before I re-engaged the electric fuel pump. With the electric fuel pump running, I was getting 26psi. I repeated this scenario multiple times on both fuel tanks during the flight. Results were pretty consistent.

It?s looking like I may have a bad fuel pump on this 1 SNEW YIO-540-D4A5. I plan on giving Lycoming a call in the morning.

My questions is there any other scenarios that I?m overlooking that may yield similar symptoms?

Thanks,

bob

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  #2  
Old 10-20-2013, 03:45 PM
TS Flightlines TS Flightlines is offline
 
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Default

Bob---any evidence of fuel being dumped overboard?
Tom
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  #3  
Old 10-20-2013, 04:36 PM
Pat Stewart Pat Stewart is offline
 
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Location: Granbury Texas
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Default

Sounds like the engine driven pump or an obstruction between it and the firewall however I assume when you checked fuel flow you disconnected at the engine driven fuel pump. if so I would start with changing the engine driven pump.

My fuel pressure readings at cruise (electric pump off) stay around 23 psi. I also assume you made full power on take off and your temps are ok. If there was a flow restriction on take off you would also see it quickly in the CHT temps. If the only time the pressure falls is when you turn off the electric pump then I would again bet on the mechanical engine driven pump.

Hope you all goes well.

Pat
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  #4  
Old 10-20-2013, 04:37 PM
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Quote:
Originally Posted by TS Flightlines View Post
Bob---any evidence of fuel being dumped overboard?
Tom

Good question. I only did the top half the post flight inspection today. I'll take a look at the drain tomorrow night when I crawl underneath to inspect.

bob
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  #5  
Old 10-20-2013, 04:43 PM
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rleffler rleffler is offline
 
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Quote:
Originally Posted by Pat Stewart View Post
Sounds like the engine driven pump or an obstruction between it and the firewall however I assume when you checked fuel flow you disconnected at the engine driven fuel pump. if so I would start with changing the engine driven pump.
I disconnected the fuel line from the fuel pump to conduct the fuel flow tests, which is why I'm not suspecting anything aft of that connection.

Quote:
Originally Posted by Pat Stewart View Post
My fuel pressure readings at cruise (electric pump off) stay around 23 psi. I also assume you made full power on take off and your temps are ok. If there was a flow restriction on take off you would also see it quickly in the CHT temps. If the only time the pressure falls is when you turn off the electric pump then I would again bet on the mechanical engine driven pump.
Yes, that was the excitement I had on the first flight. On the second flight, since I was over the anxiety of the first flight, I spent more time experimenting to identify the root cause. The CHTs settled down pretty quickly.

bob
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  #6  
Old 10-21-2013, 05:47 PM
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Quote:
Originally Posted by TS Flightlines View Post
Bob---any evidence of fuel being dumped overboard?
Tom
Not from the drain line or anywhere else that I can find.

Bob
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  #7  
Old 10-21-2013, 05:52 PM
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After shipping the data logs from my two flights and ground testing to Lycoming, they are recommending replacing my fuel pump. Naturally, I am just outside the warranty period.

They recommended a part #62B26931, which I can find that it is an approved substitute for the installed part, which is a LW15473. Anyone know what the difference may be?

Bob
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  #8  
Old 10-21-2013, 06:52 PM
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9GT 9GT is offline
 
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My buddy had a similar fuel starvation issue on his IO-360 Cozy MKIV after the first condition inspection. Turned out that the AFP fuel filter screen insert we replaced with a new one from Aircraft Spruce had such a fine micron rating, the mechanical pump could not pull enough fuel through it during a full power climb out. It would drop below 9 psi and the engine would sputter until the boost pump was turned on. Superior even went so far as to send him a new mechanical pump under warranty. When that did not help, we pulled the old filter out of the trash and compared it to the replacement. We never noticed the difference in screening as the old filter was pulled out and tossed one day then replaced a couple days later. Cleaned the old one up and used it with no more fuel pressure problems. The electric boost pump had no problems pulling the fuel through the filter but the mechanical pump on its own could not do it on a high OAO full power climb out with the fine mesh filter. I hope the new pump cures your problems.
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  #9  
Old 10-21-2013, 06:54 PM
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Bill.Peyton Bill.Peyton is offline
 
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Bob
The only thing I found was a Lycoming service letter which allows the use of the fuel pump P/N 62B26931. I don't see it anywhere. AERO in stock has the Lycoming LW 15473 Pump as does ACS.

http://www.aeroinstock.com/products/...h=TFcxNTQ3Mw==

http://www.aircraftspruce.com/catalo...elpumpLYC2.php

It's a shame they will not replace the pump with only 1 hour in service. Does not say much about Lycoming customer service.....
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  #10  
Old 10-21-2013, 06:57 PM
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Jesse Jesse is offline
 
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So, your buddy has an extra one that he can send to Bob! I like that customer service from Superior.

Lycoming, on the other hand... Man, bob! that's a bummer. Plus, it's a pain to change on a mounted engine. Sorry you gotta put up with that after just getting flying. Hope you can get it going again quickly.
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