This is actually something more for my own reference but when it comes to building, installing and then running a CIS there are a few key things that you need to check to find a problem.

• Blockages:
  
  
  • Cartridge exit port
    
  • Cartridge input port/connector
    
  • Tubing
    
  • Reservoir connector
    
  • Reservoir input port
    
  • Tubing clips? - favourite of mine: leaving the tube clips on the tubing.
  
  
• Leaks:
  
  
  • Cartridge (normal vent open?)
    
  • Cartridge exit port (any chips, dints or damage that would let air in?)
    
  • Printhead/Cartridge seals (to exit port) - especially important on Canon Pixma printers
    
  • Tubing to connectors (cartridge and reservoir ends)
    
  • Connectors to cartridge
    
  • Connectors to reservoir
    
  • Reservoir
    
  • Reservoir dip tubing (has it fallen off in the bottle?)
  
  

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Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680

Having fought with a few things this past 2 weeks I figured it's worth making a note of a few specific symptoms and the possible causes to run down to find the problem:

Symptom:
Print output starts to fade and eventually fades to nothing (ie: no print) for a specific colour

Possible Causes:

• Vent hole missing or blocked at reservoir end
  
• Tubing clamped or kinked (stopping ink flow)
  
• Tape or other obstruction over cartridge exit port (more likely cause if you've just replaced a cartridge and ink output last a few lines only)
  
• Foam build up blocking ink flow through exit port (sponge carts only)
  
• Wrong or poor ink quality causing blockages **
  
• Poor contact between receiver post and cartridge foam (Canon printer only)

** you can confirm this by checking the printhead isn't showing symptoms of blockage.. Also try a clean printhead or one known to work, different batch of ink, etc...


Symptom:
Print output shows strange banding (ie: starts solid then fades to end of left right motion then starts next band as solid and repeats)

Possible Causes:

• Tubing slightly kinked
  
• Printhead to cartridge seal ocluded or poor (ie: printing causes vaccum pressure that pulls air for part of print instead of ink)
  
• Tubing too thin for ink to flow sufficiently quickly to replace ink used in printing process
  
• ... basically anything that could reduce ink flow effectiveness

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Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680