PIXMA MP780 - Colors print very light after replacing ink cartridges

[trader_zane]

I have a Canon PIXMA MP780 which I have owned since new (~4-5 years). The last 3 times I have replaced the color ink cartridges, all the colors immediately go from printing perfect to printing very lightly. Whereas the Black 3eBK cartridge prints perfectly after replacing it. Like I said, this has happened 3 times in a row. The first two times I got to the point where I almost bought another printer. But through enough clean cycles, deep cleans, and test pages, the color finally started working. It wastes a lot of the brand new ink doing this. This 3rd time around, the excessive cleaning hasn't done the trick. I'm still able to print the black just fine, but the colors are still exceptionally light in color (maybe 20% of the normal saturation).

Does anyone have any suggestions as to why this might be happening, how to correct it, or how to keep it from happening again?

Thanks for any help,

 

[ghwellsjr]

Someone else recently had a similar problem except he wasn't getting any colors. Look at this thread and see if you can get help for your situation. Follow the same suggestions even if you don't think they apply.

 

[trader_zane]

Thanks for the suggestion and the link. I'll look into it and post my results.

 

[trader_zane]

I'm following the instructions on the link you sent for seeing if the purge system is working. I'm having trouble simply getting the windex to stay on top of the pad. It seems to soak in to the pad as fast as I can put it on there. But I'll keep trying and get back with the results.

But I wanted to re-emphasize something, this only happens when I switch cartridges. The printer works perfect, and then the instant i change the color cartridges, this ultra-light color printing starts. I don't really see how that could be a problem with the purge system. Seems like that would be bad continuously. Correct?

 

[trader_zane]

OK, I finished the 'windex-on-the-pad" trick to check the purge system. I cam back with mixed results. The first time (after my last entry) I tried, it looked clearly like all the liquid was still left on the pad. The second try, it seemed that all the liquid was gone. So I guess it might come down a needing a calibrated eye. But I ask again, would the purge system be the problem if my main issue only occurs when I switch cartridges?

 

[ghwellsjr]

Yes, once the ink starts flowing from the cartridges down through the print head and out the nozzles, you really don't need a working purge unit. But once you remove a cartridge and replace it with the same or a new cartridge, air gets into the print head and once that air gets down to the nozzles, they can no longer work. The reason is that in Canon printers, each nozzle has a very small heater that quickly boils the ink which causes it to be ejected out the nozzle and then more ink is sucked into the heater chamber. As soon as air hits the heater chamber the heater doesn't do anything (except get very hot and can potentially burn out the heater element).

The purge unit places a rubber cup with a porous material in it up against the nozzles and sucks the ink through the print head to get rid of all the air. This is especially important whenever you change cartridges. The only mystery to me is how you ever get the colors to work if it starts out light.

Once you put the Windex on the pads, you can look through a space off to the right that will give you a better glimpse of the purge pads. When there is Windex on the pads, they will look shiny, when it has been sucked away, they will look dull. It is important that you leave the cover down until all the activity stops. You don't actually have to close the cover, you can just hold down the cover switch is the black thing sticking up under the cover off to the right.

Try to determine if the Windex will stay on the pads before you close the cover and then whether it all gets sucked away after closing and reopening the cover. If it appears that only some is getting sucked away after one close/open cycle, try a second and third one without putting on more Windex. If you are finding that the purge system does not suck away the Windex, don't keep trying, just report back for more directions.

 

[trader_zane]

OK, here is the update on the purge system. I filled the pad with windex and the windex stayed around without draining outor drying up in any way. I this point pushed down the little switch on the right that indicates the top is closed. the carriage moved to the right and park itself. No noises followed. I thought this was a little odd. I'm used to hearing 10-12 seconds of noises, not just a smooth carriage slide to the right and park. Anyway, windex still there. I tried about 6 more times of closing the top or pushing the button. Each time the carriage just moved right and parked itself. Windex stayed on pad. I then closed the lid one final time and sat down to write back to you to explain what happened. Lo and behold, the printer started going through its normal gyrations. I let it do its thing to completion. Afterword, I opened it up and looked.........the pad was bone dry. So I'm interpreting that as the purge system is working.

Would you agree?

 

[trader_zane]

I've seen in the past you have suggested to people to post their nozzle check. I'm posting that along with the Super Nozzle check I saw you mention somewhere.

Here are some notes:
* the colors did not scan all that well because they are so light. On the first nozzle check, all the colors show up equally faintly with the exception of the 6BK. It didn't print at all. I need to emphasize that the 6BK was printing (albeit faintly) before I checked the purge system with the windex.
*All the cartridges in use are brand new, Canon brand.

Any thoughts?

 

[ghwellsjr]

It is very difficult to see the important details in the extended (super) nozzle check but it looks like there may be some black grid lines printing under the yellow. If this is correct, then there should have been something showing for the 6BK in the standard nozzle check. Also, I cannot tell if there is anything in the lower sections of the cyan and magenta in the standard nozzle check, can you see something there?

Maybe the next time you do the extended nozzle check, you could cut out the small grid patterns and upload them by themselves. We don't need the large pigment black 3eBK grid pattern because we can see that clearly in the standard nozzle check and we know it's working fine.

It seems that you are having intermittent behavior when you do the purge pad test with Windex. I have been working on a friend's MP780 and I have discovered that it can behave in ways that I have not seen before with regard to the purge pump test. I think the most reliable method to get consistent results is to print a nozzle check and then perform the purge pad test. When the purge system is working correctly, it will flush the Windex every time you close the cover (or hold the button down), wait for activity to stop, and then open the cover (or release the button).

When you close the cover (or hold the button down) the print head moves to the right, the print head moves down and the purge pads move up so the two come into contact with each other. When you open the cover (or release the button) the purge pump goes through its cycle which takes a short while and then the print head moves to the left.

Try doing a nozzle check before you do the purge pad test to see if you get consistent results.

 

[trader_zane]

OK, its taken me a little while to get back to this. We had a fun weekend, what else can I say?

Anyway. I ran the nozzle and extended nozzle checks again. The 6bk is working again. The 6M doesn't show up on the regular nozzle check. I couldn't get it to show up on the scan, but it is there, just faint as usual. Anyway, the different nozzle checks are here for you to look at.

I regards to the purge system test. I think the problems I was having before were just me coming up to speed on doing the test correctly. I now get perfect results every time. All the windex is sucked up and removed every time I run the test. So I would say there is nothing wrong with the purge system.

Next step in troubleshooting?