GPR will not disengage

[Gixxer]

I haven’t had this truck very long (1995 7.3 F350) and the first thing I had to do under the hood was replace the fuel / water separator. The old one had pin holes in the bottom and the water drain valve was leaking. I bought the complete assembly which included all attached sensors, wiring and a new pressure regulator. I also replaced all fuel hoses, rebuilt the IPR and installed a new fuel pump since they were accessible...and the truck had ~164k showing. Also the original owner said that the fuel pump was original and the IPR had never been touched. Checking the glow plugs, I found 5 of 8 were bad as well as the GPR. So I replace all 8 glow plugs and installed a new GPR. Now the engine starts with no smoke and runs great. Also no more fuel leaks.

Now the next problem, I‘m seeing a good bit of battery drain and I’ve discovered that the GPR will not disengage regardless of how long I run the truck. With the engine off I can cause the GPR to pick by touching a hot wire to it. Using the multimeter I can see that it works correctly and the glow plugs are being energized.

…any ideas regarding troubleshooting?