I tried everything you suggested and it didn't work. However, I came up with a test of my own and I know why it doesn't work. I created a serial cable of my own that only used pins 2, 3, and 5 and used that cable to connect my laptop to the Earthmate GPS receiver. It did not work. But when I added pins 4 and 9 to the serial cable, the GPS worked with my laptop.

But since the empeg uses those pins for something else, how can I rig something up to send whatever signal the gps needs on those pins?

I am currently running the GPS receiver off of batteries. The page oliver linked to mentions that these pins can somehow be used to power the unit instead of the batteries. Maybe if I power these pins instead of using the battery it will work the empeg? But I am not sure of how to hook it up that way. I assume it wants 6 volts since it uses 4 AAA batteries. But what pin do I connect the negative lead to and what pin the positive? I have a universal car power adapter that is no longer in use, and it can make a 6 volt charge. Does the ignition sense wire that is connected to the empeg carry 12 volts? Can I splice into that with the car adapter so that it only powers the adapter when the car is on?