Digital BW, The Print

I've given this digital black and white printing a shot but so far have failed dismally.

I have an Epson 2000P, which was quite nice in its day and even now produces good colour prints.
I decided to convert it to black and white. I purchased the 6 bottles of ink, a couple of spongeless empty cartridges, filling accessories etc. I filled the carts according to the instructions and fitted them into the printer.

There were only a few nozzles printing, and unreliably at that. There was a lot of ink on the cleaning sponge, and ink was pooling under the head and leaving big blobs along the print head path and soiling the paper. I abandoned that attempt and cleaned up the printer up and refitted the colour carts.

A cleaning cycle later and all was working properly in colour. I repeated the whole procedure again and when I fitted the colour carts back it worked fine again after a couple of cleaning cycles.

After comparing the two carts it appeared that the refillable cart was 1mm or so shorter than the original. Maybe the carts were not seating properly. I removed the close down lids, fitted the black carts, pushing them down firmly and secured them with a cable tie and some foam. The results were much better, the 4 lighter greys were printing ok, but not the black and not the medium black. Thats a bit odd as the black is a single cartridge and the medium black is one compartment in the 5 colour cart.

The end result was much better, but I couldn't get the black and med black to print without banding. There was still a lot of ink on the cleaning sponge and still pooling under the print head and dropping ink onto the printhead path.

What do I do now? If it was the print head then it wouldn't print properly in colour. Are these empty and refilled carts prone to failure.
I ordered carts for an Epson 2000P but recieved carts for a 1280/1290. Does anyone know if they are interchangeable.

Any help and advice would be welcome.

Cheers
Greg