I removed the coal load from the tender to clean the dust off the coal load and without replacing it I decided to clean the wheels.  When I fired the loco up, no sound!  I then discovered when I replaced the coal load, the sound returned.  Is a circuit completed when the coal load is in place?

Hi Everybody,
I have this Spectrum 2-8-0 that came in a nice black box that says 'DCC sound on board'.  This loco came installed with a Tsunami 16 bit sound decoder. I've had it for awhile and just last week decided to take it out of the box and test it out.  Called it up on address 3, checked the functions and started running it.  It began to stop and start randomly at any speed.  I'm using CVP's EasyDCC system.  Next, I decided to check out the CV's with Decoder Pro with my computer and using my Sprog II decoder programmer.  I tried tweaking some settings, testing it again, and found that it runs fine with Sprog II decoder programmer system.  When I move the loco over to the layout, using EasyDCC, it starts this random stop and start motion again as it rolls down the track.  The track is clean too. I've taken the locomotive apart, lubed it, checked the decoder in the tender and cannot see anything obvious to fix.  The other posts I've looked at appear to be referring to the earlier models that were made with capacitors you could clip, but this unit does not have those capacitors.
Suggestions?

Thanks, Ted