Weak spark.
 

87 turbo II has a really weak spark on both coils. Car barely runs. Any ideas?

What is the voltage in the car while the engine is running, and what makes you think you have a weak spark?

change cap, rotor, spark plugs, and spark plug wires

There is no cap or rotor on a 2nd gen US spec RX-7.

Please do not answer if you don't know!

I believe there is a distinct possibilty of either a grounding or alternator issue. If the N/A coil packs will work, I have an extra set if you need them.

I heard that the coils rarely ever go bad, not to mention that they're actually pretty good for performance.

Hey icemark, maybe hes only ever worked on eurospec sevens, HUH? ;)

Yeah living in San Fran I am sure he has....;)

oh i didnt notice i mean spark plugs and spark plug wires :)

All factory grounds are cool. I'm probably going to add more and see if that works.

Grounds will have nothing to do with the spark
again:

I'm at work so no clue on voltage, the spark is very weak on both coils. Barely visible. I checked ona standard style plug with a huge gap.

The next time the engine gets up and running and is warmed up, slowly pull one of the sparkplug wires out of the LEAD coil bore. I mean slowly and judiciously. When the wire is just coming out of the bore.....heck....held a quarter inch out of the bore, you should not be bothered anymore about thoughts of a weak spark.

Like the man said earlier, a weak battery or failing starter motor might very well be dragging down the voltage supplied to the coils which might result in a faint spark at the PLUGS. If you remove the cas and spin its gear, with the wire at the PLUG disconnected and laying on the chassis, I think you'd see a much heartier spark than you are seeing now

Don't pull the cas and do that unless you know how to reinstall a cas.

Could it be the cas itself? I can get a hold of one to swap out. I bought the car with a blown motor, but it ran a bit. The motor has been swapped out and the new engine has great compression. The car runs very similar to how it did before, Everything appears to be correct. The car itself only has 50k on it.

Slim and none that a cas will go bad. You almost have to stick a screwdriver in the guts when its spinning to make it go bad.

Spare cas??? Great. Leave the one you have in place. Take the spare and connecto it to the harness plug the present one is connected to. Turn the key to ON. Pull one of the wires out of the lead coil and let it rest on the lip of the bore where it came out of. Spin the cas gear on the bottom. Now tell me you have a small spark. You won't because it'll be very large. Do the same thing but this time leave the wire in the coil but take the wire off the sparkplug and attach it to a old sparkplug. Lay the sparkplug on or near the left strut towers strut attach nuts/studs or any good ground. Spin the cas with your fingers. I'll bet the spark will be much larger than what you've been writing about in the beginning of your thread.

If it's a lot larger, then most likely the battery voltage is being drawn down when you try to start the engine. Probably drawn down by the starter and or weak battery. When you spin the cas with your fingers as described above, there's no such draw down of power from the battery.

ohh FYI. I added additional grounds to the coils and it runs like a dream.

Where to did you run the grounds? and what gauge wire?

Coils get their ground thru the four studs that attach the coil assy to the chassis. Adding a ground wire is bogus. Period. Unless you have a rubber blanket under the coil assy and wooded studs to mount the coil assy, then a ground wire would help. (not humor)

Yep... and the only other spot they get ground from is the trigger from the ECU.

So if he thinks he has a better spark... well all the power for him. Everyone else that has worked with the system knows better.

Thats what I thought but he made think grounding the coils helped because of what he said and of what I read in the grounding how-to write up.