What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Spark Plug wires way too long

A

Airhead

Active Member
My problem was obvious as soon as I began to route the plug wires. I have a newly purchased Vans IO 360 M1B installed on my 7A. The top plug wires are 24" and 19" too long on the left and right sides, (top only) respectively. After rounds of communication with Vans and Lycoming, I have been to told they are spec'd that way to provide for different engine configurations. Really, what configuration is so different from the standard baffling shown in the plans as to require an additional 24 inches of plug wire? Color me very skeptical. Anyway I was told to just "make it work". Sound familiar?

Well, although extremely disappointed after paying close to 30 grand for an engine, I might as well get on to the "making it work" part. I have spent several hours on a method of tying up the excess wire but am not happy with any of my solutions so far. Has anyone who has encountered this problem arrrived at a method you can share?

BTW, has anyone else encountered this problem?

33uwx3t.jpg


Thanks
 
Last edited:
Yep. Same problem with the same engine. I ended up with a reasonable, although not totally elegant, routing. I'll take a pic tonight and post it.

Figured I'd live with it until time for overhauling the mags, then I'd have the harnesses made to the correct length. Not worth changing at this point.
 
Thanks Steve, I'd appreciate that. Do you think we're the only ones with this issue or have you heard of others?
 
Wires

They're probably all shipped that way. I bought my engine from a production Mooney and the wires were bundled and zip tied behind the rear engine baffle.

I just left them that way till I installed Robert Paisley's EFII dual electronic ignition system.
 
I, too, think they're all that way, but for the life of me I couldn't figure out *why*. Who on earth would have any sort of baffling/routing that would need wires *that freaking long*?

It was, frankly, a pain in the butt to deal with and made for a less attractive (albeit perfectly functional) installation of the harness.

I'm quite certain that this thread will now start to include all sorts of suggestions about making your own wires, changing to some sort of electronic ignition, etc., etc. LOL!

In the end, it worked out okay, but they'll get changed out at 500 hours.
 
Here is one solution I'm trying on for size. This clearly shows just how much too long these suckers really are. Come on, lets see some photos of these "other configuations" that Vans is refering to that use this wire length.

vmsnc3.jpg
 
Last edited:
My O320 RV-6 has been flying for 15-years. My spark plug wires run under the oil filter then up to the feed through. Yours is the first one that I have seen that have the wires above the oil filter.

My cowl is off for the installation of a Dynon EMS D10. I will take a photo of my routing on Thursday and post it.
 
Last edited:
Aw, man...I'm sorry...I totally forgot to take a picture last night for you. Will try to remember this evening, I promise.

Basically, I ran them along the top of the motor mount quite a ways out, doubled them back and then ran them into the cylinders. From there, a little routing with Adel clamps along the pushrod tubes to the plugs.

Will post something tonight, promise.
 
Airhead said:
My problem was obvious as soon as I began to route the plug wires. I have a newly purchased Vans IO 360 M1B installed on my 7A. The top plug wires are 24" and 19" too long on the left and right sides, (top only) respectively. After rounds of communication with Vans and Lycoming, I have been to told they are spec'd that way to provide for different engine configurations.

When I installed my M1B last year, I noticed the same issue. I called Lycoming Tech Support, and they said not to shorten the wires. They recommended doubling them back and forth at convenient locations (I used the engine mount) and secure with adel clamps. 100 hours later, that solution seems to be working well.

-John
Click to expand...
 
I just wonder why on earth they made them that long in the first place...you could practically run them to another engine on the front of the engine given how long they are!
 
harness

Years ago when Bendix was manufactured in Sidney NY, I had the tools to form the mag ends. I customised the harness to eliminate the exess wire. The tools are long gone and would only work on the Bendix harness. This is not rocket science if one wanted to build the proper tools to shorten the wires. It should definitely be done on the mag end.
 
elegant solution?

Bob,
it's quite evident that Van's has shipped the wrong engine mount.
You'll want to start over with the one that's 3' longer, or those wires are gonna get all chewed up in the prop!!! :)

( sorry, someone had to say it!)

Hey, while I'm here being a jerk!......anyone able to tell us where NOT to route them? with 50 zillion volts going thru, I'd think you should not run them along the engine mount, but keep them stood off an inch from each other, accessory wiring and such? I gotta say that keeping them high, clear and clean can't be a bad thing!
 
They make them all for our -540's. I had no excess to front cylinders.

I definitely would not put the excess over cylinders, creating a restriction to airflow.

The wires are insulated and if protected from chaffing/abrasion will not short to your engine mount.
 
Ideally, you should treat your ignition leads just like control cables and exhausts. In other words, they should only be attached to the engine and not to motor mounts or structures. Every time you anchor something off-engine you create a node. You'll have resulting vibrations of varying amplitude and frequency on each side. Electrical wires and stuff have to anchor somewhere and those are frequent problem areas. Very common on production planes to have over length harnesses and usually they are bundled between the mags and ty-rapped. I see a lot of guys on the homebuilts who try to route by the shortest distance. Many hang their leads off adels dangling from the rocker cover. I hate that for a couple reasons. When I've got enough length I prefer to route the bottom leads from above the rockers and pick up the baffle bolts in the cylinder head. I try to leave the rocker covers "unadorned". If you do it right, you're minimizing vibrations, chafing, exhaust cooking, and also avoiding oil soakage.
 
My routing was according to the Lycoming Harness Attach Dwg No. LD-4313-9 (see below), which came with the engine, but also was the first item Lycoming sent me after I contacted them with my complaint. I assured them I had used their drawing. Vans also includes a harness wiring diagram in the FWF plans. Virtually no significant difference, especially for the top plugs.

However, all that aside, it remains that no matter what your routing, you won't use an additional 2 feet of wire. Why bother sending us two diagrams, neither of which work!:(
34j2n13.jpg
 
Wires

You have plenty of time to mark the wires at the right lenth and send them back to the factory to have the ends shortened and send a note to stop sending out **** like that.
 
You will never see it in flight and what few ounces most of you save will more than make up with in gadgets/fancy interior anyway. Spend money and time replacing that 3003 aluminum fuel and brake lines with 5052.
 
Throw Money at the Problem

I purchased the same YIO-360-M1B from Van?s aircraft for my RV-7A and faced the same problem with the magneto harness. I had excess length in the 20 inch range. I solved the problem by purchasing a new harness from aircraft spruce. The M4001 harness fits correctly right out of the Slick box. In this case throwing money at the problem worked best for me.
 
harness

I took a wire out of a Bendix mag harness at the mag end. Really pretty simple but it appears the crimped on end would be a special item. The old ends could probably be drilled out and the shortened wire soldered in place.
 
Spark ETA ?

Seems like it would take the spark longer time to get to the plugs on those longer leads thus throwing the timing off :D
Sorry, I was just boared:rolleyes:
 
Maybe

the long wires are there to allow jump starting the guy next to you at home built parking at KOSH?? Just remember to stay away from the spinning prop(s)...


btw, my Superior wires were just right (or maybe an inch too short if anything).
 
Harness list

The manual you need to download from Slick is L1318H. It lists the harnesses from Slick and which engine they go to.

IIRC, the M4001 and the M4004 are two of the most common harnesses for Lycomings. You can order the half harness (R side or L side) but it is cheaper to buy the whole harness and then you have parts.

I had the same problem in building up an M1B and I was using a Lightspeed. I talked with a supplier and we finally figured out either the 4001 or 4004 would work, and I chose the 4004. My M1B engine adventure fell apart so I never got to see if it would have worked.

I am not sure why Lycoming said not to shorten the original-style wires because I thought you could and there are people out there who can pretty much assemble them.

I also thought that the factory certified M1B had a Lasar ignition, maybe thats why the harnesses are different???

Also, I haven't compared the routing patterns from the A1A and the M1B but they ought to be about the same. I would stick to the original pattern if you could.

harness.jpg


Dave A.
 
Spark plug leads

Guys I shortened my slick harness. Verify that the fitting that attaches to the plug isn't just pressed together rather than crimped. Mine just pulled apart and I cut to the desired length and re assembled.
 
One reason that there are two harnesses for the Lycoming 4 cylinder engines is that Lycoming has two wire layouts, with one being called an option -

wires.jpg
 
Place in Lancaster TX?

I have the Bendix dual mag system and replaced the harness a couple of years ago. The new harness was way too long even though ordered for the specific engine model I had. Someone told me a shop in Lancaster could shorten the harness for me but I never had it done. I just doubled them up and used adle clamps to secure to the engine mount.

Perhaps Walt, Mel or one of the other DFW guys know what shop I was told about.
 
Lycoming originally told me that the wires could not be "field shortened". However I eventually talked with a Lycoming tech and he send me a pdf of Slicks harness manual L-1499B and said they could be shortened according to instructions in the manual using a tool kit sold by Slick. The manual contains a list and description of the tools involved. After a review I concluded that the tool kit would probably cost more than a new harness. Really meant for a mechanic who could use it more than once. If anyone knows of a shop that can do this work, I will place them high on my "places to fly" list.

Thanks guys for the suggestions and just as important, the humor. We can only smile at the attitude of large corporations which are too busy growing the top line to worry about the bottom line..that is the satisfied customer. Well the good side is that it just makes it easier for small companys to start and flourish. I know this first hand, its paying for my RV.
 
Airhead said:
Lycoming originally told me that the wires could not be "field shortened". However I eventually talked with a Lycoming tech and he send me a pdf of Slicks harness manual L-1499B and said they could be shortened according to instructions in the manual using a tool kit sold by Slick.

--- snip ---
Click to expand...

I looked at L-1499B and it calls out T200 tool kit. Been a while since I purchased a harness but $200 at Aircraft Spruce for a few tools does appear like a lot. (Aircraft Spruce had the lowest price that I could find.)

Following are photos of how my harness is routed. Been that way for 15-years. Only slight change going from Bendix to Slick mags.

C91840FD-47D7-42E1-AA19-7319E99CB36B-220-0000000B4899ADF1.jpg


A38CBA50-3E10-4E9F-8A96-D72AE90427CA-220-0000000B253BB696.jpg


CD03EF01-BCE5-4EDF-B14A-98A4B759E334-220-0000000B02A8A6B7.jpg


3C51625D-80FE-46C4-874A-1B1F34159CBF-220-0000000ACDD62B33.jpg


93A8E064-3C56-4DD0-8EF0-F5ED10ECB6BA-220-0000000A803C243D.jpg


D17CA2BE-20B7-41D2-8E14-E648EF82E307-220-0000000AD2E0DD0A.jpg


444E170B-3319-468B-9EDE-B3F232C28DEB-220-0000000A86682BCC.jpg


8FF2628E-F08D-4FED-B222-0C2539F37F2B-220-0000000A6352B146.jpg


When I was doing the firewall forward, I have a Piper Pawnee a few hangar down undergoing restoration. I was able to go there and copy some items the way it was done for my installation.
 
Last edited:
wires

The mag end on the Bendix is just a short tapered bushing that presses into the cap from the mag side. The end of the shielding is captured between the bushing and the cap. Then a rubber?? bushing slides over the end of the wire and the wire core is crimped with a special end. A piece of steel tubing machined to proper size would be fine for pressing the bushing in place. Not sure about the crimped end.
 
You must log in or register to reply here.
Back
Top