That version of the LM2917 should not be run with a capacitor coupled input, making for a signal going above and below ground at the input pin, as stated in the datasheet for the device. You can do it with the LM2917-8 version of the device though. Simply replacing the LM2917 with a LM2917-8 might do the trick.
Alternatively, you can use the LM2917 version with the following modifications to the circuit:
1. Replace the capacitor, C1, with a 20K resistor.
2. Disconnect the ground connection to pin 11 of the LM2917.
3. Connect a 10K resistor from pin 11 to ground and connect a 20K resistor from pin 11 to +12V.
I am assuming that the tach output swings between +12V and 0V. If that is not the case then the resistor values in the modification may have to be adjusted.
The modifications given by Diver300 are prudent, especially the capacitor across the +12V power supply input, but may not be necessary.
Edit: The -8 version is not pin compatible with the straight LM2917 and other differences prevent the option of direct replacement between the two versions.