Ignition Harness Fail

[dcastor]

On my last flight I noted elevated EGT on my #4 cylinder (about 100-125 deg)...CHTs were consistent if not lower than the other 3 cylinders.  I hoped this was a clogged injector that would work itself out, but on the next run-up when I did my mag check, #4 EGT and CHT dropped to the bottom of the scale and the engine ran very rough.  After messing with the mixture some (CFI passenger suggested it might be a fouled plug) the roughness went away and I decided to continue.  On take-off roll at full power, EGT for #4 spiked immediately so I aborted.

 

Maintenance shop pulled the magneto which checked ok, but harness appeared to be "deteriorating" and #4 connection was "weak".  So, I've got a new harness on order.

 

Just thought I'd share the story for reference.

 

Dave C

[Rhumbline]

I replaced the harness (appeared to be the original) on my plane when I had the mags gone through a few weeks ago.  Though there was no noted performance degradation before, the radios are now crystal clear! 

[carusoam]

What was the cost of the harness?

I remember changing out the originals in my C, when I found the price was not terribly bad.

Something to think about if yours are terribly old...

Best regards,

-a-

[Guest]

I would hope they checked the spark plugs and then did a high tension test of the harness before they pulled the mag? Seems like the mag was pulled in error?

Clarence

[cliffy]

Clarence   +1

[Rhumbline]

What was the cost of the harness?

I remember changing out the originals in my C, when I found the price was not terribly bad.

Something to think about if yours are terribly old...

Best regards,

-a-

 

Under $400 (Kelly Aerospace) though other brands (and colors) ranged much higher.  I've no idea whether the expensive brands are worth it but I do not plan on getting 46 years out of this harness...