Are you following the instructions on page 32 of the instruction manual?
What do you mean by 'bench testing' - not using a PS3 board test assembly I assume?
Are you waiting approximately 30 seconds for the super caps to power up?
Are you using a wrist strap and anti-static mat?
If no response check the individual wiring on the engine tether and connector to the tether.
Do you have another tether you can use?
Disconnect the smoke unit - try again.
If no go, and depending on response from MTH, you may have to send the board to an MTH Certified Tech to test on the PS3 board test assembly.
bruce