MSD 6A question

[ScottNutter]

Well, it's that time of year again to get the race car fired up and start getting it ready for the season. And of course my ITA 1st gen gave me grief starting. What I noticed is that the Leading plugs don't seem to spark. Santa got me a MyChron Gold for Xmas albiet a karting model which has an inductive pickup for RPM. When I connected it to my leading spark plug wire, I got erratic if any reading on the MyChron. The trailing more resembled the stock tach.

So I pulled all 4 plugs and the fuel pump fuse and cranked the engine. Sure enough the trailing sparked the leading did not. I switched the coil wires and the leading sparked and the trailing did not. I checked the ground and both power wires on the MSD and all are good. I then checked for voltage on the + of the coil and nothing. I pulled the coil wire and checked for spark according to the MSD troubleshooting and nothing. The MSD is hooked to a new MSD coil.

Should I have 12v on the orange wire with the ignition on?

Will the multiple sparks from the MSD give my inductive pickup MyChron grief?

Any insight would be appreciated.

BTW I got this car last summer with the MSD already installed.

[lateapex911]

I have an MSD6AL in my 911, and it was a bit of a headache.

Common sense tells me using the output from the MSD will not be the best solution, and my tach on the 911 is driven from the trigger signal. Can you do this??

I had output issues as well. The MSD likes a very good supply signal, so be sure you not only have 12 volts where you need it, but that the quantity is proper. (Wire guage and connector cleanliness). And of course, make sure all grounds are good.

There is a way to test the MSD, (I think tapping the trigger to ground does it but double check that) and I can dig out the instructions if you like. But, I would hit their website firsts, as I remember they had some good diagnostic info there.

Somewhat OT, but, I had originally gotten my MSD for the 7, but as it doesn't do anything over 4K rpm or so, it was never high on my to do list. What do others think of this mod? Any before/after dyno info?

[titanium]

Scott,
You need to hook the MyChron to the tach out on the MSD box.
The MSD 6A send over 300 volts to the coil and can seriously damage any componet expecting a 12 volt signal.
You may have fried your MyChron. It's possible it has a dead short in it now. That would explain why whatever coil you hook it to will not produce a spark.
Does you car starts and runs without the MyChron attached to either coil?
You didn't say if the MSD is connected to just one coil or to both coils?

[lateapex911]

Agreed, the tach out will work on some tachs, not always on 911s though, aso I had forgotten the MSD had a tach out.

He said the MyChron used an inductive pickup, so I read that to mean something like a timing light that clips around a sparkplug wire. I would think that the multiple sparks were causing his weird tach signal, not an overvoltage.

Also, AIM has a great support staff, and they seem VERY sharp. Might want to give them a call about alternatives.

[Scott Nutter]

The MyChron does have an inductive pickup, it is a wire that will get zip tied to a plug wire. The Mychron simply led me to investigating spark on all plugs. The car will start and seems to run normal, I didn't rev it to red line because it was late but it did rev to 3K ok.

The MSD is hooked to only one coil, the one that does not seem to be producing spark.

The MyChron is currently sitting on the shelf in a box.

I was wondering if the orange wire that connects to the + side of the coil should have 12v with the ignition on?

Thanks for the responses

Hmm apears that I have 2 acounts on this board ont at home one at work.