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Changing fuel restrictors - am I missing anything?

jcarne

Well Known Member
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Hello, I am getting ready to swap out some fuel restrictors that Don sent me and wondering if my procedure is correct/ missing anything.

1. Loosen the nut and bend/swing the injector line enough out of the way to fish the current restrictor out.

2. Clean the new restrictor in a bit of MEK and dry then put in the injector.

3. Reinstall the line and tighten nut to 20-25 in-lbs. Correct torque?


I got that torque off of VAF somewhere and can't for the life of me find a torque value anywhere. Am I missing anything? Thanks everyone!
 
I don't use a torque wrench for those. However, those nuts aren't supposed to be that tight like a nut on a bolt, as you can damage the brass ball / socket fittings inside.

Pretty sure that AFP gives warnings about not over-tightening those nuts, so proceed with caution. Hopefully someone can give you a recommended torque.

Larry
 
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I don't use a torque wrench for those. However, those nuts aren't supposed to be that tight like a nut on a bolt, as you can damage the brass ball socket fittings inside.

Pretty sure that AFP gives warnings about not over-tightening those nuts.

Larry

Larry, do you just go by feel or do you have an idea on flat movement?
 
Larry, do you just go by feel or do you have an idea on flat movement?

I just go by feel. However, that may not be a good recommendation for someone without a lot of years of wrenching to develop that feel.

You need to go beyond snug, but remember that you are not dealing with nuts and bolts that support much greater torque than a fitting like this.

Larry
 
Well alby I think I just found it on AFPs website.
 

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Your instinct/recollection was correct. From the AFP site:

INSTALLING THE NOZZLE LINE
Torque the nozzle line B-nut to 20-25 inch pounds or seat the B-nut finger tight then
tighten the B-nut an additional one-half flat
 
torque values

Here's the page from the SilverHawk servo manual and the Lycoming Service table of limits
 

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One last question that just came to mind. Are injector bodies and restrictors the same between manufacturers? I have an AVStar injection system but purchased the restrictors from API. I'm assuming they are interchangeable and that I don't need API nozzle bodies first. But we all know what assuming means...

Just want to make sure my ducks are in a row before I start messing with any part of the fuel system!
 
injector body

It used to be that all were the same, but recently I saw an Avstar system that came with pressed in restrictors. See attached photos. Don knew and sent the injector body with the restrictors.

Lenny
 

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It used to be that all were the same, but recently I saw an Avstar system that came with pressed in restrictors. See attached photos. Don knew and sent the injector body with the restrictors.

Lenny

Also, the old injectors were single components without a separate restrictor.
 
Ok thanks guys. These are only about 2 years old. Sounds like I will know when I pull one of the lines off.
 
Thanks again for the help guys. I changed out the restrictors today while doing an oil change and did a test flight. It was pretty dang bumpy up there so I didn't spend too much time doing the tests but it appears from my data that I may very well be at 0 or 0.1 gph spread after only one iteration of swapping. :)
 
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