Hi,
I assume there is some buffer that contains printing data.
Is there a data interface cable?
If so, then disconnect the data cable and start the printer.
If it still starts printing, then it may be
* an internal buffer containing data (read the datasheet on how to empty this buffer)
* or the printer is defective
If it does not print.... then connect the data cable.
If it now starts to print: there will be somewhere else a data buffer (print server?) --> it's not a problem of the printer...
Klaus