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  #21  
Old 09-01-2014, 03:18 PM
bjohnson1234 bjohnson1234 is offline
 
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Location: Scottsdale, AZ
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After spending most of the day at the hangar I have come to the following conclusions:

1. The low fuel pressure is most likely not related to the engine stopping. Engine data shows the fuel pressure was normal during the taxi, runup and aborted takeoff. The erratic fuel pressure readings didn't start until I was troubleshooting on the ramp. I think they are most likely the result of the heat of the engine, a 100+ degree day and running on the ramp for extended periods. The electric pump restored normal pressure and I didn't see the problem during any of my tests today.

2. There may or may not be an issue with the servo. I missed a valuable troubleshooting step by cleaning the throttle body a second time before running the engine again, but I have not been unable to replicate any of the problems on the ground that I had yesterday.

3. The most likely cause of the engine stopping was water in the air box from washing the plane. There was a small pool of liquid in the air box when I removed it, but I'm not sure if it was fuel, water or a mix of both. My guess it that it was water because the fuel would probably have evaporated in that time. I have since drilled a small hole in the airbox to prevent anything from pooling in it again.

So, I'm left unsure if there is an issue with the servo. The engine runs perfectly on the ground now and I went through some of the troubleshooting steps, but didn't have the equipment to do others. I think my best bet is to call Don tomorrow and get his input and potentially have someone else do some testing of the servo.
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  #22  
Old 09-01-2014, 09:33 PM
Bevan Bevan is offline
 
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Do you have a drain hole in the lowest part of the airbox?

Bevan
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  #23  
Old 09-02-2014, 02:30 AM
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Arie Arie is offline
 
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In his post he says "I have since drilled a small hole in the airbox to prevent anything from pooling in it again"
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  #24  
Old 09-02-2014, 04:04 AM
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Kevin Horton Kevin Horton is offline
 
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Quote:
Originally Posted by bjohnson1234 View Post
After spending most of the day at the hangar I have come to the following conclusions:

1. The low fuel pressure is most likely not related to the engine stopping. Engine data shows the fuel pressure was normal during the taxi, runup and aborted takeoff. The erratic fuel pressure readings didn't start until I was troubleshooting on the ramp. I think they are most likely the result of the heat of the engine, a 100+ degree day and running on the ramp for extended periods. The electric pump restored normal pressure and I didn't see the problem during any of my tests today.
Where in the fuel system are you measuring the fuel pressure?
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  #25  
Old 09-02-2014, 07:45 AM
bjohnson1234 bjohnson1234 is offline
 
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Quote:
Originally Posted by Kevin Horton View Post
Where in the fuel system are you measuring the fuel pressure?
The output from the mechanical fuel pump splits and one line goes to the fuel pressure sensor and the other to the servo.
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  #26  
Old 09-02-2014, 07:51 AM
bjohnson1234 bjohnson1234 is offline
 
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I'm also planning on making some changes to the fuel line routing. The installation is non-standard and has a lot of potential to pick up heat.
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  #27  
Old 09-02-2014, 08:19 AM
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Kevin Horton Kevin Horton is offline
 
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Quote:
Originally Posted by bjohnson1234 View Post
The output from the mechanical fuel pump splits and one line goes to the fuel pressure sensor and the other to the servo.
The typical poor running at idle power with hot engine on the ground is caused by fuel boiling in the injection lines from the spider to the injectors at each cylinder. But, that has no effect on the fuel pressure between mechanical pump and servo. If you saw low pressure there during your testing, perhaps the fuel pump got hot enough to cause the fuel to start to boil there. The fact that turning the boost pump on caused the engine to run better fits this theory.

Do you have fire sleeve on the fuel lines from firewall to servo? It helps to avoid fuel boiling in those lines, plus provide additional safety in the event of a fire ahead of the firewall.
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  #28  
Old 09-02-2014, 08:47 AM
bjohnson1234 bjohnson1234 is offline
 
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Quote:
Originally Posted by Kevin Horton View Post
The typical poor running at idle power with hot engine on the ground is caused by fuel boiling in the injection lines from the spider to the injectors at each cylinder. But, that has no effect on the fuel pressure between mechanical pump and servo. If you saw low pressure there during your testing, perhaps the fuel pump got hot enough to cause the fuel to start to boil there. The fact that turning the boost pump on caused the engine to run better fits this theory.

Do you have fire sleeve on the fuel lines from firewall to servo? It helps to avoid fuel boiling in those lines, plus provide additional safety in the event of a fire ahead of the firewall.
Yea, that's basically what I was thinking. Fuel boiling in either the gascolator or the fuel pump itself. There is fire sleeve on all the FWF fuel lines. I have a blast tube going to the gascolator, but nothing to the fuel pump. It might get some air from the blast tubes for the LASAR control box.
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  #29  
Old 09-02-2014, 08:57 AM
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Mike S Mike S is offline
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Gascolator with a fuel injection engine??
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  #30  
Old 09-02-2014, 08:58 AM
bjohnson1234 bjohnson1234 is offline
 
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Quote:
Originally Posted by Mike S View Post
Gascolator with a fuel injection engine??
No idea why it was put it in there, but I plan on removing it.
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