Desert Rat
Well Known Member
Hey guys- I went up to help my buddy finish changing the engine driven fuel pump on his glass star today. Engine is an O-320.
His purpose in changing the pump was that he'd developed a problem with a high fuel pressure reading. I didn't see how a diaphragm fuel pump going bad could lead to high fuel pressure, but am willing to admit this isn't my area of expertise, so whatever.
During the post maintenance engine run I was standing next to the plane. Everything was fine at startup/idle, but when he did a runup, it started dripping fuel out of the weep hole in the bottom of the airbox. Maybe a drip every 20 seconds or so.
We swapped places and I fired it back up so he could see what I was talking about and it did the same thing again. No drips at startup, run up to about 1700 and it starts dripping, power back to idle and it stops dripping.
What the heck?
Fuel pressure is back down in the green now, otherwise I could see how you could make a case that a new pump was shoving fuel past the needle valve at high power settings, or if it did it all the time I would think that maybe the carb float sunk in the 3 months its been sitting.
I'd like to think that I'm a handy guy, but the last time I actually put a wrench on a Lycoming was back in A&P school about 30 years ago, so I'm open to suggestions.
His purpose in changing the pump was that he'd developed a problem with a high fuel pressure reading. I didn't see how a diaphragm fuel pump going bad could lead to high fuel pressure, but am willing to admit this isn't my area of expertise, so whatever.
During the post maintenance engine run I was standing next to the plane. Everything was fine at startup/idle, but when he did a runup, it started dripping fuel out of the weep hole in the bottom of the airbox. Maybe a drip every 20 seconds or so.
We swapped places and I fired it back up so he could see what I was talking about and it did the same thing again. No drips at startup, run up to about 1700 and it starts dripping, power back to idle and it stops dripping.
What the heck?
Fuel pressure is back down in the green now, otherwise I could see how you could make a case that a new pump was shoving fuel past the needle valve at high power settings, or if it did it all the time I would think that maybe the carb float sunk in the 3 months its been sitting.
I'd like to think that I'm a handy guy, but the last time I actually put a wrench on a Lycoming was back in A&P school about 30 years ago, so I'm open to suggestions.