Need Help! Changing dual Lightspeed Plasma II to Slick Mags

Ben R · #1 06-26-2016, 04:48 PM

I am in need of some advice guys.
A friend of mine decided to replace the dual Lightspeed Plasma II ignition system on his RV-8 with two standard Slick mags. We spoke with Joe at Champion/Slick support, who recommended two 4371 Slicks with dual impluse couplings based on the engine/prop combo on the plane (IO-360 A1B6 with a lightweight composite C/S prop). The dual Lightspeed system that was installed required a small battery as a backup power source in the event the aircraft battery/electrical system failed. The entire Lightspeed system was removed, Slicks installed, new P-leads fabricated and wired to the ignition switch, new plugs installed, and the mags were timed.
For some reason, the plane refuses to start. We have removed and re-pinned the mags per the Slick procedure (twice), verified timing (three times) with a timing tool, and verified spark at each plug at the appropriate time in the rotation. We have even disconnected the P-leads and attempted to start with no success. The engine will fire (only run a second or two) but only when the mixture is full lean. Any attempt to richen the mixture will cease all firing. The engine normally starts easily with no issues. We have tried starting multiple times with hours between start attempts (to eliminate the possibility of flooding during prolonged starts). There were no changes made to the fuel system or injectors. Is it possible that the Lightspeed system requires a different fuel adjustment that a standard Slick mag does not?
We are all scratching our heads. The owner is an A&P and replaced the mags on my RV-6 last year in no time and with no issues.
I plan on calling Joe again tomorrow but I'd appreciate any advice...especially if someone has made a similar swap.
Thanks in advance!!
Ben

lr172 · #2 06-26-2016, 05:00 PM

Quote:

Originally Posted by Ben R

verified spark at each plug at the appropriate time in the rotation.
Ben

We you sure they were firing on the compression stroke and not the exhaust stroke? You can confirm either by removing the valve cover. At TDC on compression stroke, you should be able to slightly compress both rockers on the pushrod side. On the exhaust stroke, one or both will be un-compressable. You can also stick your thumb or finger in the sparkplug hole, blocking the air. On the way from BDC (180* from TDC on flywheel) to TDC, compressed air will force your finger out of the hole on the compression stroke and you will feel nothing on the exhaust stroke.

EDIT: sorry, read the second half of your post too quickly. Seems you get initial firing, but then dies after 1-2 seconds. Certainly sounds fuel related. How much are you priming it? If it is kicking over in an ICO position, it had to have gotten fuel before you cranked it. You may just need to re-learn your starting technique. Any EI will fire a wider range of mixtures than a mag will. It will be a bit harder to nail the sweet spot with the mag. It will not be as easy to start as easy as it used to. Do some searches on FI starting techniques. I just converted to FI and am still learning. I still haven't figured it out yet. Lots of cranking as I learn.

Larry

Ben R · #3 06-26-2016, 05:07 PM

Thanks Larry. We did verify that we were on the compression stroke by placing our thumb over the plug hole.

N427EF · #4 06-26-2016, 05:15 PM

After removing your Lightspeed, did you plug the open manifold pressure line?
On a dual Lightspeed you would have 2 disconnected manifold pressure lines.

Ben R · #5 06-26-2016, 05:23 PM

We did plug the manifold pressure line.

Mel · #6 06-26-2016, 05:26 PM

Are you sure that the impulse couplings had "snapped" before timing?
If not ignition timing would be way off.

BobTurner · #7 06-26-2016, 05:47 PM

The new plugs are aviation plugs with a .018" or so gap, not auto plugs with a huge gap, right?
As Mel asked, are you seeing plugs fire close to TDC (since both mags have an impulse coupling)?

Ben R · #8 06-26-2016, 06:49 PM

We did make sure the impluses had snapped before timing and they are firing right at TDC. The plugs are new aviation plugs...all auto plugs removed.

C-FAH Q · #9 06-27-2016, 03:10 AM

Are you using a key switch or push buttons and toggles.? If your using a key switch, make sure it's wired correctly.

vic syracuse · #10 06-27-2016, 04:36 AM

The fact that you disconnected the P-leads takes the switch wiring out of the equation. With you verifying a spark at the correct timing, and you are sure of that, then chances are you have a fuel problem. You may not necessarily have 2 open manifold pressure ports, as common practice is to Tee them, but do check. Air/Fuel/Spark, right? Do check the fuel system and make sure you are getting fuel.

Vic