securing auto-style plug harness

A question I hadn't really thought about was raised in a thread in another forum section and I think it's a good question to post here as I'm interested in the experience of others that are using automotive spark plugs/harnesses with electronic ignitions.

Other thread was:http://www.vansairforce.com/community/showthread.php?t=33402

Question was regarding how to secure the spark plug wires at the spark plug when using automotive style ignition harnesses with electronic ignitions. The concern expressed was, what prevents engine vibration from disconnecting one or more spark plug leads.

I installed mine without any additional safetying method over the standard "snap-in" clip that connects to the plug and have not heard of others flying similar setups having issues with plug leads coming off. My installation looks like:




For those with electronic ignitions using auto plugs, what method did you use to secure the plug leads, and has anyone experienced problems in an RV installation with plug wires vibrating off?

Chris
RV-6A, almost ready for inspection & flirst flight
http://rv6aproject.ckhand.com

I have dual Lightspeed Ign. and did have a plug wire come off. The plug wires also are Lightspeeds. I think it came off because it was not pushed onto the plug far enough it must be pushed in until you hear it click into position and then I don't think it is possible to virbrate off. If one does come off it is hard to tell until you do an ignition check and then you will get some roughness. Most likely you will also have a coil go bad if a wire comes off. My coils fire two plugs each and I didn't know I had a problem until I checked the ignition on runup.

Tie wraps

We used to put a tie wrap around the boot to tighten the friction on high vibration race engines.

Works great as long as the boot and spark plug have no oil on them. Add oil and it's kinda like a wet watermelon seed.

Ted

I've had a couple customers that have the wires come off. Haven't burned out a coil yet. New plug wires and fresh Autoite 386's with the caps crimped on have stopped the occasions of wires falling off so far.

Hi temp adel clamps work very well.

Here's a picture of my installation:

Does anyone ahve any photos of how they secured the top four wires?

Two years ago I replaced the ignition harness on an airplane that had flown 27 years with unshielded ignition. The ends of the unshielded wires feature a special brass (?) clip which folds over the spark plug contact, effectively clamping it in place. This was very old, low tech solution. If anybody's having continuing problems with the molded rubber boot and spring clip style contacts on auto plugs it might be worthwhile to hunt up a set of old unshielded plug wires and see if their terminations would help resolve the problem.

N941WR said:

Hi temp adel clamps work very well.

Here's a picture of my installation:

Click to expand...

Hi Bill.

I might run that by the guys at EMagair. It may have changed, but my install manual specified that a space was to be maintained between the wires, contrary to typical aircraft practice. These are automotive type ignitions, and I think the separation is probably prudent.

I used these wire separators which you can buy at almost any auto store. The hole in the middle takes a #6 or #8 countersunk screw (I don't recall which right now) which makes it very easy to secure to a baffle or standoff bracket if needed. Most of mine are supported only by the wires themselves.

James,

You bring up a good point. I had forgotten about that but did think about the routing when I installed them. My thinking was that if I had a problem, I would change it. So far, so good.