Ok had my direct fire ignition set up last summer and worked great. Msd took a crap so went back to stock. Today I got new msd box so went to hook it back up. Simple enough right? Apparently not.
Have oarange and black out of box to the "-" and "+" of leading coil then jumpers from one leading to other leading coil.
Little red one ran to the old leading "+" for a switched power source.
Big red and black to battery "+" and "-"
Green msd wire to red dizzy wire and purple to the green dizzy wire.
Trailing hooked up stock.
Problem is when I have the trailing hooked up it pops really bad out of the carb. Doesn't make sence to me at all? Unhook trailing and it's ok? But the coil on trailing is getting power to the "-" and "+" sides? And the tach isn't working unless I have the stock leading "-" hooked up to the "-" of the trailing coil. And if I unhook it it will run for 30 seconds then die and not start. But if I leave trailing coil hooked up and pull the wire off it just arcs really bad but car runs perfect. Put it back on and pops bad again when u rev it. I don't know what the hell is going on. I don't understand because I have the trailing coil hooked up stock that worked perfectly before! And should have no affect on the leading that is ran off the msd!

 

Do you have a gutted J-109 or something else to connect to the dizzy?

Probably have a bad connection at the dizzy if you used cut up spade connectors.

Edit: Are you sure you have the leading and trailing hooked up right at the dizzy? Maybe they got swapped.

 

Sounds like T1 and T2 are going to the wrong spark plugs. It's happened to peejay. It happened to me. Probably happened to Karack too. We all do it at some point. Welcome to the club of d'oh!

 

Yes I have the wires spliced straight into the dizzy. Same way I did it before with no problems? I'm pretty positive I have t1 and t2 correct. I never unhooked the plug wires from the stock location I was running early. T1/t2 too the top plugs and other 2 coils from msd to the bottom.
Could it be a bad trailing coil? Wouldn't think so since it worked perfectly earlier that day? But I assume it shouldn't have power to the "-" and "+" sides of coil?

 

Only thing it can think of is the green and purple wire off the msd is backwards at the msd plug in? I'll have to check it out after work. Other than that I have no idea.

 

Triple checked every wire and everything is perfect. This box must be screwed up I don't know!? So I said F this and went back to stock an it runs like a champ again. Just wanted some more hp

 

Are you sure the box was firing the plugs? I usually just take one off while its running and hold it close enough to see the spark jump across the gap from the wire to the plug.

I'd say bad connection at the dizzy, or bad box.

 

lol still playing with the MSD. Try changing how its spliced into the dizzy. If it runs fine stock, it should be picking up correctly for the MSD too. Take the red/green in the dist. and swap it to opposite trigger wires for the MSD (purple/orange iirc)

 

a correct setup would be red to + off the first coil, - off the first coil to + on the second coil, - off second coil to black wire on msd.

it's called waste spark but it delivers a more even charge to each coil.

if it's still having difficulty then reduce the air gap on the pickup, they're a bit lenient with the factory air gap spec.. and leave the tach wire off initially, to be sure it isn't grounding somewhere and killing the ignition.

 

Air gap? This is what I went off. Worked perfect on old box.
http://www.smbaker.com/sand-rail/mazda-rotary-conversion/msd-6a-direct-fire-ignition-for-mazda-rx-7-rotary-engine

 

I'm positive the box was firing the plugs. Could run it with the trailing plugs off.

 

almost no one ever talks about the pickup air gap, the spec is listed in the FSM and rarely causes issues with the stock ignitors but i have seen the MSDs drop RPM signals even with the standard gap setting.

you lose almost nothing by closing the gap so i often do some tweaking to it if the car is being a pita. same goes for fuel injected cars with standalones which are having filtering issues.

 

But if I'm not mistaken I'm not using the igniter for the msd?

 

no, the magnetic pickup is a variable in every single electronic ignition setup though.

 

Rotaryevolution

Could you explain the other way to wire the box?

 

Ok today I decided to give this another go.
Went with two accel super coils instead of stock. Reworded everything and it fired right up and worked fine. I don't know what the hell was going in before?

 

Maybe interference? The MSD triggering wires can "hear" the stock ignitors if the wires are too close and not insulated. Itll make it run kinda funny.

 

I have no idea. I wired everything the same but just used aftermarket coils. Whatever as long as it works!