Hello Dave,
You find the solution to this problem? Well I have the same problem right now.
I've having this issue too, mostly because I zip tied a piece of cloth on the filament to avoid dust get into the nozzle and some of the parts I print involves a high frequency of retraction (gear moving back and forward constantly). But what directly cause the problem is the extruder gear has too much small filament particles on it and the gear won't work anymore. Check this post: http://forum.zortrax.com/index.php?/topic/2053-filament-not-loading/?hl=%2Bfilament+%2Bstop#entry24232
I've having this issue too, mostly because I zip tied a piece of cloth on the filament to avoid dust get into the nozzle and some of the parts I print involves a high frequency of retraction (gear moving back and forward constantly). But what directly cause the problem is the extruder gear has too much small filament particles on it and the gear won't work anymore. Check this post: http://forum.zortrax.com/index.php?/topic/2053-filament-not-loading/?hl=%2Bfilament+%2Bstop#entry24232
If its really it you can try cleaning:
I've found black Z-ABS (that was the color you had the issue with?) to be very troublesome.
Even though I have a z-temp fitted to my machines, I really see better prints with genuine Z-ABS and try to use it if possible.
Black is the exception...it will block nozzles regularly.
I've found turning the temp down 10 deg for black helps a bit, but it still doesn't print as well as the other Z-ABS colors.
I keep one machine loaded with black, and just change the nozzle regularly, much more often than my other machines.
I used to use a few other brand ABS's, especially blue and black, but I went back to Z-ABS because it worked best.
But I think I'll try some other blacks because I'm sick of seeing the bad prints I'm getting with that particular color.
I had clogging, too. Just leaving the nozzle in acetone didn't remove the residue in the nozzle. The burned ABS seems very resilient to acetone. Try using the needles (the steel wires inside the plastic cylinder) that came with the starter kit. I think if there is residue left inside the nozzle, it prints well initially, but new residue will cling more easily to the stuff already inside the nozzle.
I have an ultrasonic cleaner in my shop, but haven`t tried it yet for the nozzle. To clean with acetone in the ultrasonic cleaner you just put a floating metallic cup with acetone in the bath, and put the nozzle in the cup. The ultrasonic waves will transfer through the cup and clean the nozzle.
Best of luck!
Edit: I see now you did put in a new nozzle, so it can't be a clogged nozzle. You could try to rerun "insert new filament" to see if you notice anything different. The thread coming out of the extruder should be a fine "straight" thread, not curling up
Try heating the nozzle over a gas stove flame until quite hot, then dropping it in white alcohol (NOT ACETONE!).
This will burn off the carbon deposits, and the sudden cooling will release any last little bits.
Push a wire cleaner through, and repeat if necessary.
This will give you a nice clean nozzle.
What is white alcohol - methanol, ethanol, isopropanol, or something else?
I know sometimes I will soak my nozzle in acetone and clean then soak in MEK and clean just in case some Zhips has taken root inside the nozzle and that method cleans out the nozzle perfectly.
not sure if you had used Zhips at all but worth a try.
Cheers