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  #1  
Old 05-19-2022, 05:28 PM
Atanyspeed Atanyspeed is offline
 
Join Date: Mar 2009
Location: San Diego, CA
Posts: 71
Default Fuel pressure numbers

Just wondering what other IO-390 builds are getting for fuel pressure in cruise. Iím seeing 18-19 psi. An other aircraft with a 390 was showing 29-30 psi non thunderbolt Engine is running fine with good fuel flow. The engine manuals Iíve read are not clear on the psi coming out of the fuel pump as is set up by Vanís.
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  #2  
Old 05-19-2022, 05:52 PM
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Av8rRob Av8rRob is offline
 
Join Date: May 2005
Location: Rescue, CA. KROB
Posts: 450
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Quote:
Originally Posted by Atanyspeed View Post
Just wondering what other IO-390 builds are getting for fuel pressure in cruise. Iím seeing 18-19 psi. An other aircraft with a 390 was showing 29-30 psi non thunderbolt Engine is running fine with good fuel flow. The engine manuals Iíve read are not clear on the psi coming out of the fuel pump as is set up by Vanís.

Yeah thatís low. You should be getting 25-30 or so. I had to get a warranty replacement of my fuel pump at around 200 hours, so it does happen.
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  #3  
Old 05-20-2022, 04:05 AM
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Jetmart Jetmart is offline
 
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Location: Windsor, Ontario
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I am getting 26 - 28 PSI in a Thunderbolt 390 at 75% power.
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1941 Tiger Moth
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  #4  
Old 05-20-2022, 12:31 PM
Navy76 Navy76 is offline
 
Join Date: Apr 2018
Location: Corvallis, OR
Posts: 45
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Your pressure seems low to me. I typically see 28-30 psi in cruise and around 32 with the boost pump on. FWIW, Iím running an Airflow Performance boost pump and the Aircraft Specialty filters in the wing roots and no filter in the center console.
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  #5  
Old 05-20-2022, 04:13 PM
Atanyspeed Atanyspeed is offline
 
Join Date: Mar 2009
Location: San Diego, CA
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Thanks for the inputs. Iíll be contacting Lycoming on Monday.
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  #6  
Old 05-22-2022, 07:04 AM
AlexC AlexC is offline
 
Join Date: May 2018
Location: Oviedo, FL
Posts: 124
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Quote:
Originally Posted by Atanyspeed View Post
Just wondering what other IO-390 builds are getting for fuel pressure in cruise. I’m seeing 18-19 psi. An other aircraft with a 390 was showing 29-30 psi non thunderbolt Engine is running fine with good fuel flow. The engine manuals I’ve read are not clear on the psi coming out of the fuel pump as is set up by Van’s.
Also make sure your G3X (or other EFIS) is configured for the correct pressure sensor, and that the sensor's pressure range matches what is configured on the G3X (e.g. if the sensor's pressure range is 0-50psi, and the G3X is setup to use a 0-75psi sensor, your pressure would be off by 1.5x). I had that problem with one of my sensors, and a config change solved my problem.

_Alex
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  #7  
Old 05-22-2022, 03:26 PM
N49ex N49ex is offline
 
Join Date: Apr 2015
Location: Wheaton, Illinois
Posts: 162
Default Fuel pressure

Agree with other's numbers - I see 26 to 28 PSI. And agree, should check sensor/G3X correct data. BUT - my brand new Lycoming I/O-390's fuel pump leaked oil from the get go, and subsequently the replacement at 350 hours failed on take-off: watched the pressure drop and engine start to stumble, saved by the electric boost pump! So, yes these do fail, and sometimes at a remarkably young age!

Finally, you might also want to check your fuel routing and vulnerability to heat related vapor locking, as that can cause pressure drops as well.

Reinhard
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  #8  
Old 05-22-2022, 06:00 PM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,900
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Plus 1 for the configuration check, I had misconfigured mine and I was getting 18-19 PSI, changed the type of probe in the engine page and now the reading is correct.
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