I suspect that you have two wires reversed. You can read the installation instructions on the http://www.cranecams.com web site or check the full link:
http://64.90.9.168/cranecams/pdf/90002000a.pdf

It says that the black lead goes to ground, yellow to coil ground and read to coil positive. I suspect that your purple is the same as their yellow.

You can test it by turning the key on and rotating the distributor (with the cap off so you can see the slots) and the coil high voltage wire connected to a grounded spark plug (use a plug wire from the coil to the plug). Hard to describe but easy to do.

Good luck.

__________________
Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"