When things go wrong, a few common fixes are in order.
Debris in the Sprayer Connection
At times, debris like dirt and sedimentary particles clog the sprayer hose lines, which is the hose running from the faucet base to the sprayer head. Usually the particles collect in the screen at the base of the hose and sprayer head. Turn off your water supply to the faucet by closing both the hot and cold water pipe valves under the sink. Unscrew the sprayer head from the hose by turning it counterclockwise. You should lightly tap the base of the sprayer on the counter to dislodge the debris. Flush the end with clean water, and screw the sprayer back onto the hose.
Clogged Sprayer Nozzles
If your sprayer experiences a loss in water pressure, the problem resides with the face of the sprayer. This face has small nozzles that together create a spray stream. When the nozzles clog with sediments like dissolved lime or calcium, the force of the spray drops, which is only noticeable in the sprayer. Run your fingers around the surface of the sprayer nozzles repeatedly, and then use the sprayer. This is all you need to do to remove built up sediments.
Diverter Problems
If the above fixes do not solve the problem, your sprayer suffers from a clogged diverter. The diverter is the small part in the base of the faucet responsible for transferring water flow from the faucet spout to the sprayer. Shut off your water supply lines, and remove the handle by unscrewing the set screw and pulling it up off the faucet base. Unscrew the bonnet nut, and remove the cartridge. Lift off the spout, and locate the round diverter right near the faucet base. Pull this part out, and soak it in vinegar and water (half and half solution), which removes sediment deposits. Rinse and replace the diverter, and reassemble the faucet.
Sprayer Hose Problems
Inspect the sprayer hose running from the faucet base to the sprayer head for leaks or kinks. If kinks are found, unwind the hose by hand, and allow the sprayer head to rotate around to get rid of the kinks. If there is a leak, replace the sprayer hose; do not attempt to patch or repair it. Turn off the water supply by shutting both water valves. Unscrew the hose from the faucet base with a wrench, and disconnect it from the sprayer. Attach a new sprayer hose to the sprayer head, and connect it to the faucet base. Your manufacturer or a plumbing supply store has replacement sprayer hoses available for purchase.