EGT Drop to zero

Just got the 10 out of condition inspection and it was running rough with big drop on Main ignition. Shop told me to do a inflight high power ignition check.

When i switch the ignition to auxiliary and cut off the main ignition and run on auxillary, cylinders 5 & 6 both drop EGT off the to nothing and it runs really rough. Back to both or over to main ignition egt comes back up higher than the others with some roughness,

Running dual Lightspeed ignitions. Is it likely the ignition module for 5 and 6 thats gone bad? of course ran fine prior to the inspection.

The key here is 2 cylinders at the same time. My electronic ignition has one coil for each pair of opposed cylinders. Therefore:

Likely a bad coil or broken wire connection to the coil. It has happened to me twice. Both times broken wire at the connector for the coil. Vibration I suspect. Easy fix if that is the case.

I used to drop a cylinder here and there when I had aviation plugs with my dual Pmags.

The issue was the crappy Aviation Plug connectors that screwed onto the Spark plug.

It would cut the wires like a piece of copper plumbing tube.

After dealing with that I swapped over to auto plugs and haven’t had any issues since.

Point being, ohm out you plug wires first to see if you have good wires.

Anyone running Lightspeed ignitions should have a spare coil, set of pre-made wires and a few NGK plugs on the ?ready spare? shelf.

In my experience, these ignitions are sensitive to bad plugs and wires. Check the plugs and wires and swap out the suspect coil and test. If the problem is not resolved, package up the box and ship to Klaus - along with a big check.

Carl

Thanks

Thanks for the replies I am running auto plugs and they are brand new just changed at inspection. since it is 5 and 6 firing off the same coil pack I thought it might be the coil pack. Will check the connectors and the plug wires both.

randy

Checked Connections

Today I checked and replaced both connections test flew and cy;inders 5 and 6 dropped to zero on EGT when i run on the one side. Swapped coil for 3 & 4 with the coil on 5 & 6 flew again with same results.

Ideas?