Did you do a cold cylinder test?
Start the cold engine and switch immediately to the rough mag. Let it run for 30 seconds or so and shut down. spit on your finger and check each exhaust pipe right near the cylinder. (like youi check for a hot iron) If one cylinder doesn't "sizzle" you have isolated the problem to the cylinder, plug, wire or mag internal "distributor cap" (could be cracked or carbon tracking on that cylinder) If all cylinders are equal in temp its the mag. Could be coil, condenser or points. Did the mechanic set the internal timing on the mag? Bill ----- Original Message ----- From: Bill BIGGS To: [email protected] Sent: Monday, October 12, 2009 8:47 PM Subject: RE: [ercoupe-tech] Running rough on Right Mag Just a suggestion. First thing, be sure you are looking at the correct mag. Have many times seen the P-Leads crossed and guy was working on the wrong mag. Like a dog chasing it's tail. Run a tempory wire (with an alligator clip is best) from the left mag into the cockpit. Start engine and switch to RIGHT mag. Ground the wire running to left mag to the fuselage. If engine dies, your P-Leads are crossed. Bill To: [email protected] From: [email protected] Date: Mon, 12 Oct 2009 23:32:17 +0000 Subject: [ercoupe-tech] Running rough on Right Mag Folks, Back at the end of August, I flew down to Houston and Alan Fairclough and I fixed an oil leak from my #2 pushrod tubes. On the way back, I noticed an intermittent miss. The miss was not present the next time I went to fly and my mag drop was normal on both mags at run-up. We landed and went to take off again while the engine was still warm, and I had a large mag drop and rough performance on the right mag so I was able to narrow it down to a problem on the right ignition. I saw that the upper magneto harness had missing insulation and braided wire showing, so I replaced both mag harnesses and thought I had fixed the problem. Next flight, same problem-- minimal mag drop during the ground run-up on both L&R, then an intermittent miss on the right after about 15 minutes of flying. Selecting the right mag when the engine was fully warmed up led to running rough and a large mag drop. (Somewhere in here we also found the problem with the alternator and voltage regulator having been wired incorrectly and installed a new Plane Power STC'ed alternator and regulator). First, my A&P swapped upper and lower plugs and the problem stayed on the right mag. Then he did a rebuild on the Bendix mag, we re-timed everything and checked it with a mag timing box twice. The next time we went to fly, the engine ran rough on the right mag when cold, and the problem cleared up when the engine was warmed up; just the opposite of the original problem. We swapped plugs again, and the problem stayed on the right ignition. Now we're thinking it's the coil on the right mag because that's the only thing left. Any other ideas? Just to recap-- originally OK cold and running rough hot; after the mag rebuild, rough cold and OK hot. Thanks, Dave Hotmail: Powerful Free email with security by Microsoft. Get it now. _________________________________________________________________ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. http://clk.atdmt.com/GBL/go/171222985/direct/01/
