Command fails to execute in upstart session job

Command fails to execute in upstart session job

This command:
mongod --fork --dbpath ../data --smallfiles --logpath ../data/mongo.log
runs perfectly from terminal, while in directory /mongo/bin/
But, when I use same command and directory for upstart session job file (at $HOME/.config/upstart):
# mongod_service - mongoDB job file
description "MongoDB service"
author "admin"

# When to start the service
start on runlevel [2345]

# When to stop the service
stop on runlevel [016]

# Automatically restart process if crashed
# respawn

# Essentially lets upstart know the process will detach itself to the background
expect fork

# working directory
chdir /mongo/bin/

# log this job
console log

# Start mongod as daemon
exec mongod --fork --dbpath ../data --smallfiles --logpath ../data/mongo.log
On starting via initctl, I get:
>initctl start mongod-service
>initctl: Job failed to start
And no logs of what goes wrong exactly are produced anywhere !!.
Can anyone suggest how to make this work ? or at least see the error ?