I've seen that symptom described a few times, and in all cases, the final diagnosis was a bad EEC. Now, I
don't recommend that you jump to that conclusion without thorough diagnosis, but don't be surprised if that's what you find.
My first recommendation is to cut off the EEC PWR & FP relays, and install Bosch/ISO-style relays, as shown in this & the NEXT few pics:
It probably won't fix your symptom, but it needs to be done.
For actual diagnosis, run a 12V test light from a 12V source to the FP relay trigger (ground) wire in the DLC under the L hood hinge near those relays. When the pump stays on (engine NOT turning), observe the light. If it stays on, then the EEC is incorrectly holding the relay on.
