Strange starting issue

I tried connecting the power for the ECU directly to the battery and the car started right up. With the ECU connected this way the tach responded normally without the jumping around as I slowly rev'ed it up pass 2,ooo RPM. The switched power source I could find close was the blue wire running into the voltage regulator. One concern though is that during cranking it was only registering about 8 volts. I was expecting to see at least 10.5 volts. Any other good places to power the ECU?