Injectors are fed from the same relay as the ecu, idle valve and boost valve.
See: http://www.siipicossu.com/manuaaleja/engine2.jpg
Could be fuse 3 or fuse 25.
Also see: http://www.siipicossu.com/manuaaleja/engine1.jpg
Inertia switch only blocks the fuel pump as you can see above.

I assume you used a wiring loom from an Escort Cosworth.
If not, please specify which wiring loom is used.