koupster
Well Known Member
Yesterday, my left Slick mag failed an inflight mag check forcing a turnback on a Pilots N Paws mission. This is an impulse coupled mag.
Runup at 1800 rpm on the ground showed no problems.
During an inflight mag check, the engine would "hiccup" every so often. At first, I thought it was a jolt from turbulence, but the frequency increased to more than once a minute. It seemed to be a split second complete interruption of power, rather that a misfire on one or more cylinders. The power interruption was so brief that no change in EGT or airspeed was noticed. Changes of the mixture lever position, switching tanks, and turning on the boost pump had no effect.
Plugs are nice and clean (properly gapped, also) and resistances check OK (two around 1300 ohms and two around 1900 ohms). The ignition cable tester showed a spark in the window, but every so often, the spark skipped a beat and then returned. Same result on all four plug leads. This is my first time using a cable tester which was bought new. I only have a half page of instructions that I downloaded. If anyone has experience with cable testers, please chime in or contact me via email.
Am borrowing a set of plugs to test with today. It's a very long shot, and I expect no change, but it's way easier than pulling the mag. After that, I'll try disconnecting the p-lead to investigate a possible switch (standard keyed Off, L, R, Start switch) problem. I'll be careful with the hot mag.
If no solution after this, I'll be pulling the mag, and trying to find someone local that can test the mag at high rpm. If that fails,I'll be sending it out.
Any hints, advice, personal experience, or suggestions will be welcomed. I'd rather not pull the mag if it's not necessary.
Thanks.
Runup at 1800 rpm on the ground showed no problems.
During an inflight mag check, the engine would "hiccup" every so often. At first, I thought it was a jolt from turbulence, but the frequency increased to more than once a minute. It seemed to be a split second complete interruption of power, rather that a misfire on one or more cylinders. The power interruption was so brief that no change in EGT or airspeed was noticed. Changes of the mixture lever position, switching tanks, and turning on the boost pump had no effect.
Plugs are nice and clean (properly gapped, also) and resistances check OK (two around 1300 ohms and two around 1900 ohms). The ignition cable tester showed a spark in the window, but every so often, the spark skipped a beat and then returned. Same result on all four plug leads. This is my first time using a cable tester which was bought new. I only have a half page of instructions that I downloaded. If anyone has experience with cable testers, please chime in or contact me via email.
Am borrowing a set of plugs to test with today. It's a very long shot, and I expect no change, but it's way easier than pulling the mag. After that, I'll try disconnecting the p-lead to investigate a possible switch (standard keyed Off, L, R, Start switch) problem. I'll be careful with the hot mag.
If no solution after this, I'll be pulling the mag, and trying to find someone local that can test the mag at high rpm. If that fails,I'll be sending it out.
Any hints, advice, personal experience, or suggestions will be welcomed. I'd rather not pull the mag if it's not necessary.
Thanks.