"MPI" Fuse blows with key off?

[gvr4]

The MPI fuse in my GVR4 keeps blowing the instant it contacts the blades in the fuse box, even with the key off. I'll do a little more digging on it tomorrow and even bust out the service manual, but I'm hoping someone has run into this sorta thing before and can save me some troubleshooting BS.

Its blown the MPI fuse before, when I turned the key, but it has been as simple as replacing the fuse.

Car ran fine on sunday, but yesterday morning I went to start it and it just cranked, so found the fuse blown, and went to replace it, but it instantly pops, and I haven't even had time in daylight the past couple days to poke around under the hood.

any ideas?