Canon pro9000, long way to fix it

Hi,
I bought a used Canon pro9000. The seller told me, that he didn't use it for 2 years, because the rear try sensor is broken. He had some sheet feed parts as well, because he thought need to replace it. The ink cartridges were in the printer, half of them were dry already. Anyway, I don't have money for a new canon pro printer, so I bought it.
One time I could fix a canon printer, but this time I will need some help. Lots of things to do, so please keep checking it until I can print my first image with it.
I connected to my laptop, I turned it on. I saw 7 orange flashes. I opened the access cover and 1 continuous read, 7 read flashes from the print head. I removed the ink cartridges. I washed gently the print head in water. Then I put it in an about 15% ammonia water, wash it again and now it's still in a diluted window cleaner solution. The ink is still coming out from the head.
I didn't take the cover off from the printer, but I will do like this: http://www.printerknowledge.com/threads/removal-of-top-cover-from-pro-9500.9961/
Where is this broken sensor come from? Where was it in the printer? (He gave it in my hand) From where can I order a new one, or anyone can send me one?

@BMate, Seven flashing orange, refers to the cartridges

Some ink tanks are not installed in the correct position. (The lamps on the ink tanks flash.)
More than one ink tanks of the same colour are installed.
Confirm that the ink tanks are installed in the appropriate positions.

So before you can begin to use the printer again you’ll have to have proper full CLl-8 cartridges to test the printer, but be sure to dry the print head thoroughly before re-installing it again, if you take any shortcuts you may well damage the print head.

I will PM you the service and parts manual, which should help you locate the damaged parts..

Thank you for your quick reply!
Yes, CLI-8 inks are on the way.
Thank you for the parts manuals. I can't decide which part of this. Maybe the QM2-3458-000 SENSOR MULTI HARNESS ASS'Y. The black part and the yellow cable is the same, but the other end of the cable is different.
At the weekend I will take the cover off and I can check it. I will post the result in here!

This weekend I took the cover off from the printer. When I thought this sensor should go, there is a sensor like this and no other place where it was missing.
I put back the cover.
Print head is still out from the printer.
I turned it on and this time I could see 3 orange flashes (paper jams). This was the original problem I thing, therefore he gave me those paper feed parts to replace it. During the quick check I realized, that something moving in the printer. Maybe a screw.
I turned it on again. Now I had 5 orange flashes, print hear is not installed. Yes, it's true.
So now I'm waiting for the inks, then I will put back the head + inks and I will see what kind of error message will I get.

@BMate, I am wondering if you should cut you losses now before they grow any further because the first error maybe be the one that will cause you the biggest headache. (Paper jam)

If the previous owner got a paper jam and removed this jam by pulling the obstruction out backwards then the sensor for decteching paper in the machine may have gotten damages or broken, only time will tell.

If you can't repair the printer yourself, it is better to dump it rather than send it to Canon for their technicians to look at, it will be very hard to get spare parts and it might be better to short out or disconnect the sensor all together, if that is possible..

Can you show me a photo about that sensor, that how is it looks like and where is it?

BMate said:

Can you show me a photo about that sensor, that how is it looks like and where is it?

Click to expand...

I reckon it’s probably the one in your photos on your first post 1#..

I thought the paper jam optical sensor is looks like this:
http://www.fixya.com/support/t6575512-canon_mx310

That is the paper sensor on the exit of the printer but there can also be a mechanical one on the entry side, it usually has a small piece of protruding plastic sticking up in the paper path that gets moved out of the way when the paper passes over it.

I could fix it after 2 weeks.
On the above picture you can see the back door sensor. Someone could fix it. Now it's in open position to be able to use front feed.
Other problem was with the paper sensor. As soon as the print start, the paper wants to move and activate that sensor. During printing I need to hold it and it's working.
The previous owner damaged the TIMING SLIT DISK as well.