Forced landing 11/06/11

[HighWing]

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

[DesertFox4]

Thanks Zorro for the update on your fuel problem. Sometimes issues like yours take a methodical step by step approach to find.

It makes me wonder about regularly checking the clamps and giving a little twist. I wonder if this is a good idea.

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.

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.

[kitfox2009]

Great advice, Steve.

Cheers
Don

[Zorro]

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.

[szicree]

Perhaps fuel pump is overpowering right side carb float when you're at full throttle.

[jamesmil]

hi guys after looking at the pic,s of plugs i would say that the right side carb is very rich but the left side carb is running extremely lean to the point of fuel starvation. the ground strap is showing signs of discoloration from high heat and the porcelin insulator is clean. not as clean as we would see on a race engin after a clean cut but those plugs tell me to look at the float levels in both carbs.
it looks like the float is to low or there is trash in the needle and seat or trash in the high speed jet of the left carb.
i would also check the float leval on the right carb. hope this helps

[jtpitkin06]

Just a thought... have you tried bypassing the fuel pump and running on gravity feed alone? Without the pump it should run on the ground just fine. Do not fly it this way! This is for a test to see if the fuel pressure is too high and if the carb has any problems such as a float valve problem.
If it runs OK without the pump, look to the float valve.

If it still has a problem, reconnect the fuel pump and swap the carbs left to right to see if the problem follows.

You're going to find the problem, it's just a matter of eliminatiing everything step by step.

JP