ahhh, I know its pathetic, going to keep going up the line, maybe slyfox will be right and I'll end up with all new fuel lines. BUMMER IT WAS NICE OUT TO. I might have to rent the citabria and do some lops and spins to vent my frustrations.
Thanks for all you input
Just like my experience - enough flow to partially empty the carburetor bowls during run up and refill during taxi to the take off point, then emptying on full throttle climb out and having just enough fuel for rough running - mine ran at about 3500 RPM so easy to do a gentle return to the runway. I wouldn't be surprized if you already found the problem with the shut off valve malfinction. Good work. One more thought I had a Facet pump just down stream from the header tank with the on switch thumb distance away from the throttle. It went on immediately with the rough engine and likely helped a bit with fuel flow.
Lowell
Last edited by HighWing; 11-26-2011 at 10:57 PM.
I found it at last, you folk were right on the track, flow was 8.75 gph at every point except 1, the hose exiting the gascolator, I saw that the hose didn't cover the whole barb, and the hose clamp (recently tightened) It closed over the top of the barb, This also caused the barb to cut into the hose, making a flap like check valve, the more fuel I demanded the harder it closed off the flow! So a 24 inch hose worth 8.50$ could have been a disaster.
Thank you every one I hope this thread contributes the grater good.
Happy Days, glad you found the problem.
Dorsal ~~^~~
Series 7 - Tri-Gear
912 ULS Warp Drive
This is the second report of a "recently tightened" clamp issue. Mine makes three if you want to consider the firesleeve clamp. It makes me wonder about regularly checking the clamps and giving a little twist. It is exactly what happened in the first instance about ten years ago - give a twist every annual. I wonder if this is a good idea.
Lowell
Thanks Zorro for the update on your fuel problem. Sometimes issues like yours take a methodical step by step approach to find.
Lowell, I've done it also and for several years I've had to tell myself every conditional inspection not to mess with any hose clamps. If I'm actually replacing the hose due to a leak or deterioration then new clamps are used and an initial tightening with a follow up check a couple of flights later then I leave it alone if it ain't leaking.It makes me wonder about regularly checking the clamps and giving a little twist. I wonder if this is a good idea.
As for flow testing: A fuel flow test is absolutely critical to execute before first flight. You have to know your engine will be receiving enough fuel to keep it operating at full throttle plus a good safety margin. I tested my system with the tail touching the ground as in a take-off/climb attitude. Mine being a tri-gear makes that fairly steep.
I would think a flow test would be a good practice also if ever you make changes to your fuel delivery system such as adding different type fuel filters , adding or removing components like gascolators or re-routing fuel lines, adding or removing secondary fuel pumps, fuel shutoff valves, changing header tanks ect. Last place you want to learn you have a reduced fuel flow issue is shortly after take off when many of your options have evaporated. Be safe out there guys.
DesertFox4
Admin.
7 Super Sport912 ULS Tri-gear
Great advice, Steve.
Cheers
Don
well after testing the problem is still there. The fuel is flowing great. I had written a test flight plan, and never got past the full power run up.
27 seconds into the full power it did exactly the same thing.
I pulled the plugs the plugs and all 4 plugs on right side are black and carbon covered on the left they are perfect.
Perhaps fuel pump is overpowering right side carb float when you're at full throttle.