service mongod start command not working

Server is 3.0.3
OS : CentOS 6.x
The "service mongd start" command is not working.
"service mongod stop" command works fine.

Here is the conf file

processManagement:
fork: true
pidFilePath: /var/run/mongodb/mongod.pid
systemLog:
path: /var/log/mongodb/mongod.log
logAppend: true
destination: file
net:
port: 27017
storage:
journal:
enabled: true
dbPath: /mongodb_data
security:
keyFile: /var/lib/mongo/rskey
replication:
replSetName: RS-xxxxMongo-0