philperry9
Joined: 23 Nov 2011
Posts: 381
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 Posted: Thu Sep 07, 2017 7:27 pm Post subject: Fuel PSI Fluctuations - Update |
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For the past few weeks, I haven't had much time to fly. But it's getting better tomorrow I hope to fly some more and hopefully get knocking on the door of retiring Phase 1.
I am not willing to claim 100% victory yet, but I've managed to make some good progress on the fuel pressure fluctuations and the rough engine.
After searching for leaks, contamination, etc. I finally zeroed in on heat forward of the firewall. My tunnel is cool to the touch so it had to be forward.
I had mentioned that I re-routed a fuel line away from exhaust and that helped smooth out the engine quite a bit. But there was still a hint of roughness. Not bad, but enough to make you sit up straight in your seat.
I manufactured some heat shields and clamped them on to the fuel lines coming into and out of the engine driven fuel pump. Protecting from exhaust heat.
That appears to be the secret to the rough engine. Last two flights have been great. The fuel PSI fluctuations were reduced from 4 psi in cruise to about .5 psi. Good progress!
My fuel pump cooling shroud came in, and knowing the heat shields made a difference, I stared down my fuel pump and picked the fight. After a simple 4 hour swap earlier, this time that (at)&$%# beast fought me at every turn. 2 days and 11 hours of shop time later, it was installed and test run. I hate fuel pump replacements now and my hands are chewed up and bruised from this one.
I flew it again tonight and the cooling shroud didn't make any incremental difference.........though I suspect it will still be beneficial once we get back to the hot Texas weather again.
Here is a video from tonight in cruise.
https://youtu.be/x3geLPYmuyU
I was still seeing about 4 psi fluctuations in climb but in cruise it was back in the .5 range.
Engine is running well and .5 doesn't seem that bad once you're stable in cruise. So I'm going to let it go until it becomes a problem or some symptoms begin showing their face. So far it's what you want out of the airplane.
My next thing to try is focusing on the sensor. I'm going to re-crimp the sensor wires to make sure that's not contributing to it. And maybe, someday, I might replace be sensor.
But at least it's safe now and running like you'd expect. Takes a load off and it's nice to be able to relax a bit and not have to sit straight up in the seat the entire time. 
Phil
Sent from my iPhone
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