Based on the manual 6-12V is acceptable between pins 10 and 11. This is for the rpm signal.

It's the power input to the coil of the relay that's low at pins 9 and 11. Reading should be 11-14 V. Probably you have a poor ground connection or the incoming power is grounded somewhere. Also what's your battery voltage?

Just wondering, are your electrical centers (battery and fuse box areas) dry?