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  #1  
Old 07-25-2021, 11:18 PM
mechmike mechmike is offline
 
Join Date: Feb 2020
Location: Powell River
Posts: 8
Default Iron grit in carb bowl MA-4-5

I felt and heard a faint, intermittent, stumble during my last flight. Came and left every 12 seconds or so and stayed for maybe 4 seconds each time.

Cyl temps all equal, carb heat and mixture didn't fix it, normal mag drops, normal fuel pressure.
I changed tanks and it seemed to go away and then switched back and it was still all good. Landed 10 min later perfectly normal.

Checked the gascolator and the finger screen in the carb both perfectly clean. Tanks sump clean. I drained and flushed out the float bowl and found a fair bit of what looks like black iron grindings (magnetic). Couple particles are larger than the rest and definitely shouldn't have made it through the finger screen.
What's inside these carbs that would make this?

The finger screen had nothing in it and I have no reason to think it wasn't seating in there, it's not collapsed at all. But even if it could have gotten by it, where would this material come from? (post gascolator)

Any thoughts?

Thanks
Mike
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  #2  
Old 07-26-2021, 05:28 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 6,537
Default

Not too much ferrous material in the carb but some. Unlikely it came from outside the carb if material is easily visible. Seems a tear down and cleaning is in order. I believe the casting is zinc and nonferrous, but not sure.
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  #3  
Old 07-26-2021, 06:31 AM
WingsOnWheels WingsOnWheels is offline
 
Join Date: Mar 2009
Location: Plano, TX
Posts: 2,231
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Possibly contaminated fuel from a rusty storage tank. The particles settle in the bowl and collect together. Worth looking in your wing tank as well. Just a thought.
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  #4  
Old 07-26-2021, 10:23 AM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,531
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Check the Lean Mixture valve on the bottom of the float bowl. If the valve base was pressed in slanted, it might cause wear on the rotating valve shaft. (While in there make sure the valve base is well secured to the bowl, this caused a very interesting end of a flight for me once). This is only metal on metal area I can think of other than the accelerator pump plunger.

Is there anything inside a fuel pump that could cause metal?
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Last edited by Ralph Inkster : 07-26-2021 at 10:26 AM.
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  #5  
Old 07-26-2021, 08:48 PM
mechmike mechmike is offline
 
Join Date: Feb 2020
Location: Powell River
Posts: 8
Default

Quote:
Originally Posted by Ralph Inkster View Post
Check the Lean Mixture valve on the bottom of the float bowl. If the valve base was pressed in slanted, it might cause wear on the rotating valve shaft. (While in there make sure the valve base is well secured to the bowl, this caused a very interesting end of a flight for me once). This is only metal on metal area I can think of other than the accelerator pump plunger.

Is there anything inside a fuel pump that could cause metal?
Ralph. That's the thing, why isn't the black iron grit in the finger screen in the carb or the bottom of the gascolator ?..... must have originated in the carb. I'll look at the valve base.

Thanks
Mike
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