Index: leahi_dialin/dd/modules/piston_pump.py
===================================================================
diff -u -rf9dd375900151a5daafe3b687187187645d5f1ab -r4e60dc04a4526be59962b3be2cb149b9bf536623
--- leahi_dialin/dd/modules/piston_pump.py	(.../piston_pump.py)	(revision f9dd375900151a5daafe3b687187187645d5f1ab)
+++ leahi_dialin/dd/modules/piston_pump.py	(.../piston_pump.py)	(revision 4e60dc04a4526be59962b3be2cb149b9bf536623)
@@ -144,7 +144,7 @@
         cyc = integer_to_bytearray(count)
         spd = float_to_bytearray(speed)
         vlm = float_to_bytearray(volume)
-        payload = pmp + cmd + cyc + spd + vlm
+        payload = pmp + cmd + cyc + vlm + spd
 
         message = DenaliMessage.build_message(channel_id=DenaliChannels.dialin_to_dd_ch_id,
                                               message_id=MsgIds.MSG_ID_DD_PISTON_PUMP_START_STOP_OVERRIDE_REQUEST.value,