Quick and dirty spark plug wires

[tjts1]

My 318i had been running for 158k miles now on the original spark plug wires from 1991. They even had the cosmoline coating to prove it. Something had to be done. Replacement wires cost between $110-$270! depending where you look. Another obvious and ideal choice is COP conversion for about the same price. I was looking for something quicker and cheaper. I noticed my GF's Volvo 850 has much shorter spark plug wires with the same type of connector on the coil end. Then yesterday at the JY I came across an 850 with new looking spark plug wires and so I decided to give it a try for the grand total of $5.

The 850 had 5 cylinders with 5 wires coming off the distributor. The shortest wire (pictured bottom) is just about 1" too short for cyl #1 on the M42. The longest M42 stock ignition wire is (are you ready?) 4 feet long!

I used the 4 longer 850 wires and routed them forward, away from the exhaust.

The tops of a 850 wires at the spark plug end have a large rubber ring that I had to cut away with scissors. Ghetto but effective.


So the result is much smoother idle. I can't believe how nice it runs and a bit better throttle response. I'm going to check it periodically for the next few days to see how its holding up. New 850 wires can be had for about $35-$50.
http://www.fcpgroton.com/category-exec/category_id/226/nm/Ignition_Wire_Sets/sub_top_menu_item/by_make-by_model-by_year/by_make/78/by_model/1136/by_year/46/

"Performance" wires (whatever that means, a spark is a spark is a spark), can be had for $90
http://ipdusa.com/Volvo-850/Filters-&-Tune-Up/Ignition-Tune-Up-Parts/Spark-Plug-Wires/Spark-Plug-Wires-ipd/p-72-167-242-658-647/

[Cobra Jet]

the only problem I see with the "quick fix" is:

1) the top of the spark plug chamber is not 100% sealed as it was when using correct M42 wires

2) due to the sealing issue, if any water or moisture gets into the engine bay, it's going to go right past the top of the "modified" Volvo wires and right into the spark plug chambers.  If there was (or is) enough water/condensation/moisture to do so, you're looking at an engine that could misfire or the possibility of water getting past the spark plug threads into the cylinder.

I'm sure you saved a decent amount of $$$ and it's a "temporary" fix to get you up and running again, but just be careful and keep an eye on the situation as noted above.

[tjts1]

Thats a good point but try pouring a cup of cold water on a hot engine. It will boil off and evaporate long before it has a chance to accumulate in the spark plug wells. I could see this being a problem if I was parking outside in a big rain storm with the hood open. If you've ever has a chance to work on an older engine like a chevy 350 for example, the sparkplug wells are not sealed up because this is a non issue. The seal on the stock wires is there to keep out dust a debris that could fall into the combustion chamber when removing the sparkplug. The solution is a qick burst of compressed air into the well before replacing the plug.
cheer

[D. Clay]

I filled two of mine with water the first time I cleaned the engine after doing the COP conversion. A piece of plastic during motor hose offs solved the problem.

[nomad]

if the rubber boots are on, then it can keep water from leaving. Also, these engines get beastly hot anyhow so yeah, it won't be a problem for long.

Good thinking though, especially for those who just need to get going and have no cash.

[tjts1]

Also keep in mind that the coils sit just 6 inches from the spark plug wells yet the stock wires are between 42-48 inches long. Even the longest volvo wire is just 18 inches long. If I made some custom wires I could reduce that to just 12 inches. The resistance of a spark plug wire increases proportionally its length. COP is ideal in this respect.

[nomad]

I was thinking the exact same thing. Just enough slack for engine movement and you can do a straight shot to the plug holes.

It actually looks like those wires are a better length than the stockers too. I may go this route and eliminate the old stuff. Certainly cheaper than stock replacements.

At Home Depot they have large flat rubber washers too. Maybe 4 of these would be good to slip on the ends as simple water splash/dust guards.

[SnPaC]

This is an attractive option.

Has anyone else tried this?

[melloh]

Would you be able to get pictures if you do get the washers?  I have no idea what the age of my wires are, but I am guessing they are original.  For piece of mind (and maybe fuel economy) I want to change them.  I have been contemplating the COP route, but this seems much similar and cheaper.  In both cases, my main concern is dust/debris.  It's ReALLY friggin dusty where I live.  This is where your solution becomes exponentially more attractive!!!

At Home Depot they have large flat rubber washers too. Maybe 4 of these would be good to slip on the ends as simple water splash/dust guards.

[tjts1]

The stock Volvo 850 spark plug wires have a huge rubber ring molded into the boots.

I cut the whole thing off because it was too bit for the M42 sprark plug wells. If you were careful you could cut them to the exact diameter of the M42 wells.

[nomad]

picked up a set of good looking wires from an 850. Plan on trimming to make a nice "grommet" fit in the spark plug holes.
I'll report back how it goes. Thanks for the DIY!

[mkodama]

Thats a good point but try pouring a cup of cold water on a hot engine. It will boil off and evaporate long before it has a chance to accumulate in the spark plug wells. I could see this being a problem if I was parking outside in a big rain storm with the hood open. If you've ever has a chance to work on an older engine like a chevy 350 for example, the sparkplug wells are not sealed up because this is a non issue. The seal on the stock wires is there to keep out dust a debris that could fall into the combustion chamber when removing the sparkplug. The solution is a qick burst of compressed air into the well before replacing the plug.
cheer

It takes only a drop of water and the spark can short and the cylinder won't fire.  And you say that water will boil off, but that was only partly the case in my situation.  

The spark plug wells were partly sealed which allowed for a small amount of water to get in.  And when the engine was cold, one of the cylinders wouldn't fire.  After it heated up, the water evaporated somewhat and the problem would go away.  But once the engine cooled, the water would condense again and the problem would come back.

This wasn't in my 318 but my Toyota Landcruiser.  And it is a pretty noticeable effect when one of the cylinders doesn't fire.  Other than the engine running really roughly, it would amount to about 30-40 hp being lost.

[nomad]

So I installed these today. Routing is sort of funky but the OEM volvo wire clips were helpful. I cut the entire lip off of each wire as well, they then fit down into the cyl to plug onto the sparkplug. One thing I may do, to solve the above stated problem, is to trim off the M42 plug wire "cup/boot" section and slip it over the spark plug hole. This works as i tried it on one already. You basically end up with a little cup that slides down over everything and the wire comes out of the middle like the M42 ones.

Started the car up and everything seemed as it should be. Didn't notice a "difference" but happy to get (newer) wires.

The only issue I didn't like was that the Volvo boots don't "click" into place like the OEM. Only the wire end on the coils did. It would be nicer to have the feel of a positive "snap" engagement, other than a "slide on". We'll see how it goes. Needless to say I'm keeping my OEMs in case of an emergency.

[tjts1]

Try pressing down the boots harder. It took some pressure to get mine to click but they did eventually. You can't hurt them.

[nomad]

The wires I got had light grey connector tips for the plugs, maybe they are a little bit different. Worked fine though.