7ECA losing power

R

rgarrett

New member
I have a 7ECA with a O-235C1. I'm having a problem after takeoff with reduced power. Takeoff roll is normal, developing around 2400 rpm. After getting airborne by perhaps 100' the power drops down around 2100 rpms. It will then begin to fluctuate up and down roughly in that range. I had a similar problem a couple months ago and had the carb rebuilt. It didn't fix the problem so the A&P sent the carb back for a 2nd look. They did some further work and it seemed to fix the problem. The current problem however seems to be very similar to the one experienced earlier and while I've flown the airplane a couple times without a problem it is now not clear to be if the initial problem was ever fixed. The engine doesn't seem to run rough. It is more like the throttle is being decreased and then increased again.

The tank vent is clear, another A&P had the carb off yesterday and saw nothing wrong with it. I've spoken with Lycon about flow testing the carb. They will flow test it but they have said that the problem I describe doesn't sound like a problem the the carb. They said the carb is so simple it works, or it doesn't.

Anyone run into this before or have ideas? I'm going to start spending more money next week and I'd like to decide where to spend it first. I've tried to find a replacement carb but that hasn't gone well. Everyone wants to rebuild mine (since that has been done, twice, I'm not sure that would solve the problem even if it is in the carb somewhere). I did find one rebuilt for $1000 plus my core but I'm reluctant to spend that much when it sounds like there is a good chance it isn't the carb.
 
had a similar problem years ago with a j3 cub. went thru the carb a couple of times. changed the air filter,and about drove myself crazy. once i convinced myself it was a fuel flow problem, i started at the tank and went thru the fuel system. i found the problem in the sediment bowl. the filter was partly clogged. allowed fuel to flow enough to do run ups and ground checks, but once asked to perform at take off and climb, it just did not allow enough fuel to get thru all the time. seemed as though some else was controlling my throttle. replaced the filter, and all was well. hard to find, but probably the cheapest fix i've ever had on an airplane, LOL. good luck
 
Thanks. Checked the sediment bowl and screen and all looks okay there. It does seem like a fuel flow issue to me. The tank vent is clear too.
 
I would check and make sure that the carb heat is not on. It soulds like the cable might be letting the carb heat door open and reducing the power. Its something to check at a low cost. I have found this on a few aircraft in the past.

Richard
 
I have an O-235 in my 7AC-CONV Champ and have had a similar problem with two different causes. As someone already suggested....carb heat. The first time, the carb heat flap wasn't all the way closed but the knob was to the panel. It ended up being the cable was flexing enough but not closing the flap (opening actually). I had to rebush the heat box and recut the little notches on the box also. The other time (times in this case) it was the primer. If it isn't seated correstly the carb draws a minor extra amout of fuel and cause the engine to run overly rich causing less RPM. Check all the primer lines for cracks/breaks also.
Good Luck,
WW
 
One other item you might want to check - the muffler(s).

If the internal baffling has come loose, it could back up the exhaust, like the banana-in-the-tailpipe trick. When the airplane is level, it runs fine, but as soon as the nose comes up, some of the junk drops toward the tailpipe and blocks it, resulting in a huge drop in RPM.

Hope this helps,
 
I second checking the muffler. My only forced landing in 40 years of flying was caused by a bad muffler, and before it quit it was causing symptoms like yours.

Bill
 
Well..... maybe it is fixed. The exhaust seems to be okay as does the carb heat. The A&P called this a.m. and found a bug in the fuel line at the fuel cutoff valve. I spoke with the prior owner a few days ago and he said that after he bought it he found a mud dauber at the fuel cutoff. I haven't flown it yet but I think that could explain the power loss.

Thanks to each of your for your comments and suggestions.
 
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