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fuel pressure tap fitting

C

cguarino

Well Known Member
I just swapped out my RSA-5 fuel servo and the fuel pressure tap hole is different. My original servo had a 1/8 pipe thread hole with a AN3 elbow in it. The new servo has a a plug that looks like 7/16-20 straight thread (I'm just guessing about this thread size). The plug that is currently in the tap has an o-ring. So how do I go from the straight thread to AN3. It needs to be an elbow fitting. Looking for the nomenclature and source. I don't want to reroute my fuel pressure line. Thanks in advance.
 
Last edited:
cguarino said:
I just swapped out my RSA-5 fuel servo and the fuel pressure tap hole is different. My original servo had a 1/8 pipe thread hole with a AN3 elbow in it. The new servo has a a plug that looks like 7/16-20 straight thread (I'm just guessing about this thread size). The plug that is currently in the tap has an o-ring. So how do I go from the straight thread to AN3. It needs to be an elbow fitting. Looking for the nomenclature and source. I don't want to reroute my fuel pressure line. Thanks in advance.
Click to expand...

O-ring boss fitting...?
 
Not that easy

I don't think the pump fittings will work. I don't know what thread they are but I think they are way too big on the AN flare side. I need an AN3. There must be a fitting for this. The bendix manual labels the port as "fuel pressure tap". Is anyone pulling their fuel pressure from this port? Thanks.
 
I'm confused...you're taking fuel pressure off of the FI servo? I thought that came off of the engine-driven fuel pump, not the servo???

Am I mis-remembering something?
 
either will work

The Bendix fuel servo has a port right above the fuel inlet. It is open to the cavity that houses the inlet screen. Bendix calls it the fuel pressure tap. The builder of my airplane used it instead of tapping the pressure at the pump. You could even argue it is the best place because it measures the fuel inlet pressure in the servo. Take a look a bendix cutaway and it will be obvious. Thanks.
 
Aha...I was looking at the Precision Airmotive manual, and it's there, but not labeled (and I think that's what they refer to in the text as the Alternate Fuel Outlet). I found the Bendix document which does label it Inlet Fuel Pressure Tap.

Learn something new every day! :) Thanks!
 
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