Looking for a single spark plug cable!

J

JeffFranks

Filing Flight Plan
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Jul 19, 2008
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Jeff F
I have a 172H with a Cont O-300 and Dual Slick 6364 Mags. During run-up last week, we had a hard miss show up on the left mag. After pulling the cowling and doing some troubleshooting, I was able to determine that the problem is with one of the spark plug cables (ignition harness). The threaded end that screws onto the sparkplug is stripped out and hasn't been making good contact. Signs of arc'ing are on the wire and I can't get it to 'grab' the threads to put it back in place. Its noticably stripped (almost smooth) inside the collar where the threads are, so it explains some of the 'missing' I thought I'd felt in cruise over the last few months.

Anyway, the rest of the ignition harness is fine. I'm just wanting to replace ONE cable, not the entire $350 harness. Does anyone know where I could find good used cables like this or even a replaced harness that I can pull one good wire out of?

We have a second used harness (with a different magneto connector, but the correct plug side) and were going to try to replace the stripped out collar, but that's not a great option since the 'stops' are made into the cable and will be a bear to move to the new cable. Not to mention, probably not safe/FAA Appoved :)

Google has failed me for the first time!!!! :)

Thanks for any advice!

jf
 
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You da man! So, what you're saying is that google hasn't failed me....I simply don't know what to call what I'm looking for! :)

Thanks so much. I've learned my 1 item for the day (Spark plug cables are called Ignition Leads :) ).

jf
 
This sounds identical to the failure I experienced in the 182 at North Platte recently.

The mechanic there had no difficulty finding a single plug wire assembly to replace the broken one with at all. I swear he also said something about them being able to be fabricated from parts and he would have just repaired one end of ours if the plug wire hadn't been just a touch too short. Maybe an A&P could elaborate here, on cars I've never used anything but a pre-build plug wire with ends already on it.

Seems like at high voltages, any mistakes made putting on the connector would be trouble. I'd prefer the whole wire assembly get replaced.

Sounds like you've got a line on 'em now anyway... Don't think single wires are all that rare, though.
 
JeffFranks said:
I have a 172H with a Cont O-300 and Dual Slick 6364 Mags. During run-up last week, we had a hard miss show up on the left mag. After pulling the cowling and doing some troubleshooting, I was able to determine that the problem is with one of the spark plug cables (ignition harness). The threaded end that screws onto the sparkplug is stripped out and hasn't been making good contact. Signs of arc'ing are on the wire and I can't get it to 'grab' the threads to put it back in place. Its noticably stripped (almost smooth) inside the collar where the threads are, so it explains some of the 'missing' I thought I'd felt in cruise over the last few months.

Anyway, the rest of the ignition harness is fine. I'm just wanting to replace ONE cable, not the entire $350 harness. Does anyone know where I could find good used cables like this or even a replaced harness that I can pull one good wire out of?

We have a second used harness (with a different magneto connector, but the correct plug side) and were going to try to replace the stripped out collar, but that's not a great option since the 'stops' are made into the cable and will be a bear to move to the new cable. Not to mention, probably not safe/FAA Appoved :)

Google has failed me for the first time!!!! :)

Thanks for any advice!

jf
Click to expand...

If you have a second harness remove the proper length lead and put it in the harness that you want to use. Do you know how to change the lead? the shell of the lead isn't your skip, the arcing is, the whole lead needs to be changed, and it comes out after removing the mag end of the lead.
 
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Directions for removing a bad lead.

the mag cap has the leads installed with a cone driven in from the front side of the cap. remove the rubber insulator and use a end cutter plyers, to remove the cone holding the shielding into the mag cap, and the lead will slide right out.

install by reverse order. slide the end of the lead into the mag cap, slip the cone over the center core wire trapping the shielding between the cone and the cap and smack with a deep socket and a mallot, then replace the rubber insulator and spring.

new leads can be bought from TCM
 
denverpilot said:
This sounds identical to the failure I experienced in the 182 at North Platte recently.

The mechanic there had no difficulty finding a single plug wire assembly to replace the broken one with at all. I swear he also said something about them being able to be fabricated from parts and he would have just repaired one end of ours if the plug wire hadn't been just a touch too short. Maybe an A&P could elaborate here, on cars I've never used anything but a pre-build plug wire with ends already on it.

Seems like at high voltages, any mistakes made putting on the connector would be trouble. I'd prefer the whole wire assembly get replaced.

Sounds like you've got a line on 'em now anyway... Don't think single wires are all that rare, though.
Click to expand...

You can manufacture new leads to "Repair" a harness, by buying all the parts and cable, but you need special tools to do it, most A&Ps don't make them, they use used leads ro buy complete leads from many sources.
 
Tom-D said:
He need not pull a mag to change a lead, just the back cap. 3 screws and the harness is off.
Click to expand...

But you can look for

  • Erosion or burning on towers
  • Color differences in lead contact buttons
  • Carbon dust
 
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