Reduction in Power - why?

BloomerJohn · Post by **BloomerJohn** » Mon Apr 05, 2004 3:37 pm

I should say the problem on the left side continued for the entire duration of the 2.5 hr flight. Mag check was just a bit rough 5 hrs later when the engine was cold, then went bad again once in the air and continued 2.5 hrs back home.
What is this lead tester you spoke of?

mrpibb · Post by **mrpibb** » Mon Apr 05, 2004 4:22 pm

What would be done is to remove the leads to the plugs that you want to check, and the harness block on the back of the mag side of question. The tester hooks up to the battery and to the center conductor of the lead you want to check. With the tester turned on there is a vibrator and coil inside the creates a high voltage, also there is a window on the face of the tester that will light up if the lead is not shorted, if there is no light then the voltage supplied to the lead is shorting thru the shield of the lead. the tester looks like this
http://www.aircraft-tool.com/shop/detai ... ?PageNo=15

A lot of places sell this tester, and somtimes find them used too.
Vic

Post by **GAHorn** » Mon Apr 05, 2004 8:02 pm

John this is beginning to sound more like a condenser that is breaking down as it heats up, or possibly the coil. The condenser is less expensive, so you might try replacing the condenser or swapping them L/R if labor is free.
But before you do, I should also mention that this is the same symptoms I had last year when my left mag ran poorly, but only did so occasionally. It turned out to be the magneto oil-seal was leaking oil into the distributor cap. Replacing the seal (only two years old since mag rebuild) took care of the problem. So, when you look inside the mag, look for oil before you arbitrarily just start replacing parts.

Walker · Post by **Walker** » Mon Apr 05, 2004 9:12 pm

With antique mags that are a big pain to take apart to swap condensers, I have hooked up a condenser to the ground post as a test. If you do have a bad condenser, you will almost certainly need to deal with the points too. Heat expands things, and in the case of a mag, the expansion can create shorts. It cools a little and the problem goes away, but always comes back. If somebody has been spinning the mag over with no leads to ground, it creates pathways that help the shorts find their ground.

BloomerJohn · Post by **BloomerJohn** » Thu Apr 15, 2004 4:07 pm

Put new plugs in top (L Mag) Have run for 2.5 hrs...Equal drop on both sides. and smooth!!
Thank you for the tips!!

BloomerJohn · Post by **BloomerJohn** » Fri Apr 16, 2004 10:28 pm

New plugs installed in top (left Mag) test flew for over 2.5 hrs. Equal mag drop , smooth as a turbine now. Thanks to all.
John