[Shad]

I experienced a problem with my 125 tonight at the flying field. First flight of the year with the plane. Start, idle, take off and climb out were all good. On the second or third decending pass at full throtle the engine dies to a high idle but continues to run. I pull the throtle back and punch it again and it's up to full power until it is in a decending pattern again, then the same thing happens. So far I have bypassed the full filter, richened, and leaned the engine up to 1/2 turn each way, used fresher fuel, checked the clunk, cheched all fuel lines and tank, bypassed the fuel filler valve and still can't see anything wrong with the set up. I went through three tanks of fuel and the problem was consistant the entire time. There is a good smoke trail from the plane as it flies and then no smoke and the engine dies to idle. Pull the stick back and then power up and the smoke reappears and the engine will run fine until sustained full throtle and it starts to rev out a bit. I have had this engine for over 3 seasons and it has certainly broken in. Help!

[williame3590]

glow plug??

Bill

[Cougar429]

Only time I ever had a motor react this way the 138DP PCM Rx was telling me the pack voltage was low. It drops the throttle and will not follow your commands until you lower the throttle stick and then throttle up again. It only allows you full control for another 30 seconds, then repeats this routine.

[Shad]

I thought about the glow plug but wouldn't that mean that the engine would not run or start or fly as consistant as it did? I will certainly give it a try. Any other ideas?

[Cougar429]

Other than what I mentioned and regardless of all your fuel system work, this still seems a fuel delivery problem. The fact your smoke trail decreases sounds like you are leaning out.

The fact this occurs nose down suggests the clunk is physically not following the fuel to the front of the tank. I find this an issue on some tanks due to the silicone line being too stiff.

Is there a way to simulate this on the ground, with the A/C on a table perhaps with the nose protruding off the end? This would definitely be a two person operation.

[dean2287]

Tank height OK?

[flysrcs]

Brad,
Weather looks good for a flying sessiion tonight. bring your RV to the field and sure we can figure it out.
Dave

[Shad]

Thanks Dave.
I have something on the go with my daughter at the school tonight so I can't be at the field. Karl was with me last night and it sure was puzzling.