Delphi printing to Zebra printer

Delphi printing to Zebra printer

I have written a function that prints out ZPLII data to a Zebra printer as
shown below
StartDocument(DocName);
StartPage;
Try
For I:=0 to DataToPrint.Count-1 do
Begin
St:=FormatPrintLine(I);
Try
Escape(PrinterHandle,PASSTHROUGH,Length(St),PAnsiChar(St),Nil);
Except on E:Exception do
begin
GetWin32ApiErrorMessage(FErrorCode,FErrorText);
Raise EPrinter.CreateFmt('Printer Write Error %d'+#13+
'While Printing To '+PrinterName+#13+
ErrorText,[ErrorCode]);
end;
End;
end;
Finally
EndPage;
EndDocument;
I have tested the label data by using the command prompt to print it from
a text file and the label prints out correctly but i cannot print it from
my application. If i pause the printer i can see the job gets sent to the
printer and the size of the job is 2.12Kb, roughly the size the label
should be, but nothing prints out. The light on the Zebra printer for data
lights up but nothing will print. I have tried this with two of the Zebra
printers we own, so it is not a printer issue. My guess at this point is
that maybe the program isn't sending the entire label data to the printer
and the end is never received but when i trace through the send request,
everthing is sent properly. the printer also shows the job has 0/0 pages
for the label but i cannot understand why it is not sending the label. Is
there something special that needs to go at the end of the label data
besides the ^XZ termination character? I am also using Delphi XE3 if that
helps.