Blinking alternator light, no spark, electrical gremlins

[MichiganMat]

I'd hoped I wouldn't have gremlins in my project but here I am. Here are the basics:

- 1975 911S chassis + harness + panel
- 1983 3.0SC engine
- no lambda brain
- fuses are all good
- new hi-torque starter
- wires are new magnecore
- jumping from my truck battery until I can use my lightweight batt.

Turn on the ignition and I get:
- fuel pump running whirring, lots of gas
- whinning from the CDI
- the coil is sending out a death-spark to ground

Turn the key:
- engine turns over, new hi-torque starter motor
- spark from the coil wire goes dead
- voltage at panel goes wayy down
- engine no start

It looks like the starter, or something else, is pulling so much energy from the battery that there isn't enough voltage to run the CDI box. I've brushed the heck out of all the grounds and connections, checked the ground strap, etc, but its not kicking over. I've tried 2 different CDI boxes and 2 coils now. I've searched around Pelican but no one seems to have had this issue:

"no spark when trying to start, plenty of spark when sitting idle"

[MikeBogue]

I think that the blinking alternator light is a parking brake indicator. Have you checked the signal from the distributer to make sure that you have a good signal to the coil? Did the 3.0 run well before it was installed?

[MichiganMat]

I could use some suggestions if anyone has any!

[Staylo]

checked the green wire?

[Jagshund]

Are the fuel pump and CDI still active when you turn the key?

[MichiganMat]

I put a light on the power to the CDI and it dims significantly when I try to start the car. I cleaned up the grounds to the panel but it didn't improve. Could it be a fuse? Maybe the connection at the ignition is bad? What would cause a huge loss of power on start?

The starter is a brand-new hi-torque starter

[HawgRyder]

Sounds like the main ground from the engine to the body is not connected.
Also....check the ground to frame connection at the battery.
Bob

[MichiganMat]

So I checked the voltage and current draw on the CDI, both are going down significantly when trying to start.

The voltage across the battery goes down to about 6v during starting which is (Im betting) too low for the CDI to generate a spark.

this. sucks.

[JP911]

Matt-
What was the solution to this problem? I recently created a similar situation with my car and I can't figure it out.
-Jon

[MichiganMat]

Yeah, I figured it out.

With the ignition on, the CDI box was fully operational and spitting out hellfire at the sparkplugs, but during cranking (trying to start) the box would go dead and would not provide spark.

I found it by unplugging the signal line from the CDI to the tach. Strangely then the car started right up.

Solution: The wiring of the engine harness (the 14pin plug) was incorrect and was feeding god-knows-what from the CDI to the rest of the car. Rearranged a few pins to their correct positions and she fired right up.

[JP911]

Interesting. I think my issue is similar, but not exactly the same. Thanks for the info!