How to get rid of a black strip (1") on the leading edge of scanned documents?

the page is not against the glass,you need to close the lid tight

Dear Lyris
pl. do the margin setting of the document as well as paper. The setting of scanning may be done up to 4mm leading edge and left edge up to 2.5mm.
Thanks.

The black lines are caused by either marks on the scanning strip or a fault with the scanner. If there are no marks on the scanning strip then there's nothing that can be done without sending it for repair. Details of the cleaning procedure are shown in the instruction manual.

Sounds like the shading compensation strips may be dirty and/or sticking. Otherwise the scan sensor is going out.
To check and clean the the shading compensation strips:

Open the feeder up all the way and hold down the red stop button.
...in about 5 seconds the upper and lower shading compensation strips will pop up.

They may be getting stuck and not popping out all the way (about 1/2")
Clean them up with a small brush and a lint free rag with alcohol.

If the shading sensor strips aren't popping out all the way, this will cause the problem you described, so clean them up and repeat this several times.
(They pop up during the document scanning process)
If they still aren't popping out after cleaning them up, then there may be a mechanical problem with the mechanism.

Hope this helps! You may need a tech.
I am in Dallas, Texas if you are local to me I can put an eye on it.

You need to change the mylar strip on the ADF and also you need to clean the narrow strip of glass that the scanner uses for ADF scans. The Mylar strip is found by opening the lid, as you do when you put a document on the glass. On the left side you will see a Mylar sheet that covers a white backing section. There is a latch on the front and back of the Mylar mount that allows it to drop down. There should be spare Mylars in an envelope tucked under right edge of the white backing strip for documents placed on the glass. Just be sure to orient the new strip the same as the old one. The mylar strips can sometimes be cleaned but usually it is better to replace it if you have spares.

Open the Applications folder on the hard disk on which MP Navigator is installed, then open the Canon Utilities folder and double-click the MP Navigator 3.0 icon. MP Navigator opens.
2. Point to Scan/Import and click 'Photos/Documents (Platen)'.

3. Place the document face-down on the platen glass, and select 'Document Type'.
How to place the document and Document Type depends on the document to be scanned.

How to place the document
Allow 3/8 inches (1 cm) or more space between the edges of the platen glass and the document.
Align a corner of the document with the corner at the arrow of the platen.

• When you select Color Photo or Black and White Photo, the position or size of the image may not be scanned correctly if you do not leave 3/8 inches (1 cm) or more space between the edges of the platen glass and the document.
  
• When you select Color Photo or Black and White Photo, the position or size of the image may not be scanned correctly depending on the document. In such a case, select Document Size such as A4 or Letter according to the document to be scanned.
  
• When you select Magazine(Color), the Descreen function will be enabled and scanning takes longer than usual. To reset the Descreen function, disable Descreen in the Scan Settings dialog box.

4. Click 'Specify'... and set the preferences as required.
The Scan Settings Dialog Box opens. Specify the Document Size and Scanning Resolution.

• When Document Size is Auto Detect or Auto Detect(Multiple Documents), the position or size of the image may not be scanned correctly depending on the document. In such a case, select Document Size, such as A4 or Letter according to the document to be scanned.

5. Click 'Scan'.
Scanning will begin.
When the document has been scanned, the scanned image is displayed in the Thumbnail List area.

The thick line is either because of dust sticking to the glass or a module problem. Try different brightness settings and scan white paper. If the thickness varies and also the sides of the black strip are jaggered (step like) then it is dust on Glass. use isopropyl alcohol to clean, dont use solvents. If the teickness is same for all levels of brightness and has a sharp edge always, it could be scan module problem.
S. Mohan

check on the flat bed part along the top. there are two white strips that go side to side. the top white strip is wider than the bottom strip right underneath it. On the thinner of the two strips, check for small black marks, can be very small. This creates a black line in the document. You can clean it with a fingernail & a tissue

There is a small strip of glass on the left side directly under the edge of the scanner, About a half an inch wide. It has something on it.
May be very hard to see, use a strong glass cleaner or some alcohol and a regular piece of paper to clean it with.

Take glass cleaner and clean the small strip of glass to the far right. If there is a speck on that strip of glass it will cause a line when it scans.