I have a e350 ambulance,I am getting 12.2 on the volt meter and its not starting on 1993 Ford E-350

I purchased 2 920 cranking amps batteries and when I tumble the motor it seems to tumble slow

Asked by for the 1993 Ford E-350
diesel i assume. ck starter for amp draw.
Hi,thank you for your to check for amp draw?
3 more answers , 1 more comment
Also, have alternator checked for proper recharge levels.
you could have a bad starter
The starter was just serviced,thank you.
is battery voltage at the starter?