The pullout spout leaks

• Take out the plug button on the front side of the faucet handle and loosen the set screw with your Allen wrench, then pull off the handle. Remove the domed cap underneath the handle by unscrewing it.
• Take off the entire spout by removing the mounting hardware under the base and lifting the spout up and off the faucet. The hose will be attached underneath the counter. Once you unscrew the connector, the spray head can be removed.
  

If its leaking from the base of the spout where its attached to the body, its most likely the O rings that need replacing. The spout body could also be leaking as the metal is quite thin and can develop pin holes under the bottom face of the spout. To determine it that's the problem, turn the water on, place your hand under the spout body, you should not get any water spray, if you do (its usually a fine mist so its hard to see, but you will feel it) the spout is bad, replace it.

Usually, it is caused by a worn out o-ring.

Replace that washer and tighten well.

Take it back apart and check the placement of all the o-rings and or seals.
The low water pressure may be no more then the aerator being dirty where the water comes out of the spout.

If there is a hole on the spout itself then you should go ahead and replace th.e whole faucet. This will save you both time and money in the long run

Sounds like the diverter is not working properly. It is located in the spout and it maybe sticking or bad. Go to link below for a installation guide with parts break down. Click on installer's and designer's bar below picture of faucet for a diagram of faucet that may help you out.

http://www.us.kohler.com/onlinecatalog/detail.jsp?from=thumb&frm=&module=Faucet+Collection+Kitchen&item=9559802&prod_num=10433&section=1&category=4&resultPage=0-711729362

before you take it apart ,I want you to check,the pullout handle first,because most of the time ,all that is wrong is that little1/2-5/8 in washer between the handle and the hose,It usually runs down the hose ,and might apear to be something else leaking under the sink.If your correct,and it is leaking where you said.Some of the newer faucet have a clip that just pushes together.So you need it fing the clip,and push it in.

most of the the pullout sprayers need a rubber washer were it meets the hose chek for cracks and replace.

I have a Hansa pullout kitch faucet that leaks out of a hole in the back when faucet is shut. Is this a bad backflow preventor and how do I fix it?
I can't get the spout off to access the body of the faucet.
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I have the same problem. Have you had any luck?