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bmiles
Joined: 17 Jan 2010
Posts: 12
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 Posted: Tue Apr 13, 2010 1:35 pm Post subject: Magnito Issue Maybe.... |
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When I conduct a runup on my CJ (at) 1860 Man Press and check the Mags, the engine makes a popping sound and Man Pres Bounces up and down on both Mags until it's about to die. If i leave it on both mags and advance the throttle, the engine just about dies and then seconds later does what it's suppose to do.
After completing a flight, I performed a runup and when the throttle was advanced the engine quit. My friend thinks it might be Mag Timing.......
Any ideas? Carb?
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dsavarese0812(at)bellsout
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| Posted: Wed Apr 14, 2010 4:34 am Post subject: Magnito Issue Maybe.... |
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I don't believe it to be mag timing. Certainly check it though. Did you try advancing the throttle with it only on one mag at a time? Based on what you described, it sounds more like fuel starvation. Have you replaced any of the fuel hoses recently? Check the fuel screen and also the finger screen in the carburetor. It could also be the diaphragm in the carburetor has fractured.
Dennis
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bmiles
Joined: 17 Jan 2010
Posts: 12
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| Posted: Thu Apr 15, 2010 5:23 am Post subject: Re: Magnito Issue Maybe.... |
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I tried advancing the throttle on each Mag and the engine just about dies. Before it dies it makes a pop popping noise as if (my guess) Sparks are jumping.
My fuel filter is good, diaphragm in the carburetor was checked about a month ago, and I have never changed the fuel lines, maybe Ernie did before I bought the plane.
A friend of mine thinks it's the harness and that we should replace it....
Any thoughts
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dsavarese0812(at)bellsout
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| Posted: Thu Apr 15, 2010 6:22 am Post subject: Magnito Issue Maybe.... |
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Please consider doing the automotive conversion kit. It solves the wiring harness problems that are prevalent in both the Housai and M14 engines. You can read about it and download the instructions from my web site, http://www.yak-52.com/plug_conversion.htm or you can call me to discuss the conversion.
Dennis
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yakplt(at)yahoo.com
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| Posted: Thu Apr 15, 2010 2:07 pm Post subject: Magnito Issue Maybe.... |
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It is hard to believe it is an ignition issue if it is doing it on both mags equally bad. You also mentioned earlier that if you leave it on BOTH mags operating, you can advance the throttle, it pops a lot, and then seems to run better and work correctly.
Is this true? Can you advance the throttle and get PAST this popping and then it runs OK?
Try advancing the throttle very very VERY slowly and see if it impacts how things happen and give a very detailed report of what happens. Step by step. You simply can't say too much, but you can easily say too little and leave out an important detail.
To ME, this sounds like the engine is going lean as you advance the throttle. The POP POP sound is probably the engine going lean and having some kind of backfire, or pop in the exhaust itself. It just FEELS like it is fuel related.
If you can just CREEP the throttle forward a tiny bit at a time and get by this and then when it gets up to a certain RPM it starts running better, it IS a fuel thing almost certainly.
Two things... take a VERY VERY close look at your intake tubes! If you have an intake drain kit, make darn certain that all those lines are good and there are NO LEAKS! When the engine is at idle it is drawing a vacuum and as you advance the throttle, if you have a massive leak, you will draw in fresh air, the engine cylinder will go lean, and it will POP. Once you get past that a bit, you will develop more positive pressure in the tube and it will start to richen up and fire because of the blower.
These are all wild ass guesses based on just my own past experience with intake leaks on a number of different engines. I mean, look CAREFULLY for any kind of intake leak. Flange nuts, joints, big cracks, splits... I mean look CAREFULLY!
Second... it might be something really bad wrong in the carb.
A lot of people are more expert than me on this kind of problem. However, the more details you can give will end up giving you more accurate feedback. They are not there, they can not hear or see what is happening, so it is all on you really.
One clue to me is the manifold pressure bouncing up and down when it starts popping. This is to me an indication of an intake backfire.
But all this could be totally wrong.
Mark Bitterlich
p.s. A very dangerous trick to find this kind of thing is to have the engine idling, and then using very very quick and brief shots, squirt in some starter fluid around intake areas where there may be a leak. If you have it at idle and all of a sudden the sound of the engine changes, you have an intake leak right there. A lot of people use WD-40 instead to do this, which is not quite as dangerous. I am not saying you should do this, as it is possible to cause a disaster in the process. Starting fluid is ether and man oh man... you are literally playing with fire. I have NEVER done this on an aircraft engine. NEVER! I have done it on car racing engines, and they are a lot safer. In any case, I would NEVER use the starter fluid idea on an aircraft engine, just too damn dangerous. WD-40... maybe.
--- On Thu, 4/15/10, bmiles <miles(at)wambua.com> wrote:
| Quote: |
From: bmiles <miles(at)wambua.com>
Subject: Re: Magnito Issue Maybe....
To: yak-list(at)matronics.com
Date: Thursday, April 15, 2010, 9:23 AM
--> Yak-List message posted by: "bmiles" <miles(at)wambua.com (miles(at)wambua.com)>
I tried advancing the throttle on each Mag and the engine just about dies. Before it dies it makes a pop popping noise as if (my guess) Sparks are jumping.
My fuel filter is good, diaphragm in the carburetor was checked about a month ago, and I have never changed the fuel lines, maybe Ernie did before I bought the plane.
A friend of mine thinks it's the harness and that we should replace it....
Any thoughts
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dsavarese0812(at)bellsout
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| Posted: Fri Apr 16, 2010 3:37 am Post subject: Magnito Issue Maybe.... |
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Mark,
Your point about the intake tube gland nut seals is right on the money. We had one CJ that actually had a couple of the seals missing and the owner chased the problem for weeks. Finally the intake tubes were pulled and low and behold.....no rubber seals on the end of a couple of tubes. Pulled all the intake tubes, replace all the seals and bingo....problem solved.
Dennis
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