No ink flow on Big BLACK for Canon cartridges

CISS for Canon MX870
I've installed my CISS to find I can not get ink flow for the Black Ink 520 BGBK
I've run over a dozen cleaning cycles with no improvement.

Trying different things, I noticed when I remove the black cartridge and then refit it, I am able to print 1-2 pages fine before it runs dry (same effect when a regular cartridge runs dry)

I've gone a step further and removed all the cartridges, raised the ink reservoir to force ink to flow. All colours flow and leak out of the cartridge, the black does not.

I can not see any kinks, bends or other defects in the feed tubes.
I've double checked the ink flow switch is not compressing any of the ink tubes.
All small plugs have been removed from each ink reservoir.

Hi Sebastian,
I think you have bought your CISS on 10/2012.probably you have not used it until now. if you do not use the CISS for a long time the pigment black ink dries up in the line and it blocks the tubing,
to fix the problem you can put the external tank up side down,pull the pigment black tubing from the bottom of the tank and also pull out the tubing from the black cartridge and cover it with tissue.blow air to the tubing with syringe and needle from the tank side to remove all dried ink.
put the tubing back to the bottom of the tank(with a pointy nose pliers.
open the plug of the tank hold it higher than the cartridge for a short while to re-prime the tubing.when the tubing is full of ink tighten the roller clamp and put the tank on the table and put the tubing elbow back onto the cartridge.
please put on gloves before you start the job.

If you think it is a difficult job you can send the system back to us we will fix it free of charge but you should pay for shipping cost.

Best regards,
Help disk

5/36 O'Riordan Street
NSW 2015
Phone: 02-80655614 / 1300 213 589
Fax: 02-93103375

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Unit 2 / 11 Jullian Close, Banksmeadow, NSW 2019 (Sydney/Australia)
Phone: 1300-213-589, +61 02-8065-5614 Fax: +61 02-93103375