1972 911 No Spark Problem
 

Hello,

I have a 1972 Porsche 911 that's been sitting for a few years and I'm trying to get it back on the road. I changed major fluids and installed some rebuilt Webers. When I went to start the car I had no spark, no headlights, no turn signals (all fuses are good) even though it was running fine when I stopped driving it. The battery is new, a test light attached on the body ground strap and the probe to the battery ground does not light up the probe so I don't think there's a open circuit or short. The MSD 6AL box and MSD Blaster II coil are both good as I can get a spark if I use a test lamp with the clamp on rear fuse box (top fuse) and the probe touching the middle fuse on same block. With the key off and coil center wire with a spark plug attached and close to ground the spark shows every time I touch the probe to the center fuse end. However, I have no spark if I turn the ignition key to run (with the center coil wire attached to a spark plug close to ground) or when I remove the white MSD points wire and tap to ground (should spark every time I tap to ground). I don't know if I'm bypassing the ignition run position by connecting the test light and getting a spark, but my only thought is a bad ignition switch? Any thought before I start changing out relays, switches etc.?

If the fuel pump is running I would think the ignition switch is good. I suggest you get a cheap digital meter and start checking you have 12V where you should with the key on. The fuse mounts and fuses are prone to corrosion so they may look good, but need a clean up. I would be surprised if a test light probe can supply enough current to backfeed the ignition circuit and fire an electronic ignition.