My toilet tank won't fill with water unless I lightly touch the top of the fill valve on the left hand side of the tank. I have a santa rosa kohler toilet. As soon as I touch it or jiggle it a bit the tank fills up with water and flushes fine but the tank won't refill again. How do I fix this? Thank you!

Which type of fill valve do you have?

The one on the left - 400A. Thanks!

All I have to do is jiggle the "arm" and the tank fills with water.

I did a little more experimenting. I have to actually put a little pressure on the "arm" clockwise -- a very slight movement results which also turns the black "float" on diagram 400A slightly clockwise. Then the water starts filling the tank from the bottom and from the tube that goes into the overflow pipe. Thanks!

Purchase a Fluid Master seal (shown below).
Turn off the water at the stop valve underneath the toilet tank.
Remove tank top and put in safe place so it doesn't get broken.
Reach in and underneath the float, lift the float and grasp the shank.
Turn the black cap 1/8 turn counter clockwise.

Replace seal.
Reinstall cap, turn on water and adjust water level to 1" below the top of the overflow tube.
See these videos.

REMOVING CAP ASSY FROM A FLUIDMASTER 400 SERIES FILL VALVE - YouTube

How to fix a toilet: replacing the Fluidmaster 400 fill valve seal (HD) - YouTube

Oh wow... thank you so much. It may take me a couple of days to do this. I'll let you know how it goes. Thank you again!

Dear hkstroud and massplumber 2008,

I did as both of you suggested and replaced the seal. Now the tank fills with water after flushing but the water is constantly running. I can see that the water is filling past the waterline in the tank, but don't know how to adjust it so the tank only fills to the level it did before.

Thank you!

Also, I just realized that water is leaking into the tank from under the black cap and from right where the refill tube attaches between the black cap and float. I have tried to adjust the new seal under the black cap but that didn't help. :(

Two way of adjusting a Fluid Master fill valve. There is a long plastic screw that adjust the float up or down. It's that long screw that attaches the float to the lever that stops the flow of water.

The other way is for major adjustments. The shank of the valve is two parts. There is the part of the shank that is bolted to the bottom of the tank. It has a spiral thread around it. The other part is the part that has the float and shut off valve.
The two parts of the shank can be adjusted to different heights because toilet tanks are different heights. Before you install it you adjust the valve to fit height of your tank.
You can adjust it down (shorten it) by simply pushing down.
To make it higher you have to unscrew it. After you have installed the valve you usually don't have enough room to twist the float part and screw it up or down.

However, if you look at the shank down under the float where the two parts come together you will see a gray (usually) ring. If you pull that ring up (water turned off) you unclamp the top and can adjust the entire float and shut off part up and down. Then push the gray ring down to lock things back together.

Rereading you post. I don't think you have the cap back on properly. Take it off and try again. Remember to remove it, you have to lift the lever as you turn the cap.

I have the metal rod that connects the float to the shut off arm, not the long plastic screw. I tried squeezing the metal clip and adjusting it to different levels but the water keeps running. I will try to adjust the height of the valve from the gray ring. If the tank is filling up past the waterline, do I lower the height of the valve or raise it? Thank you!

I have taken off and put on the cap again several times to see if I had put the new seal in properly. The seal seems to be in place fine, the cap seems okay, but eventually some water keeps coming out from under the black cap. Should I try to adjust the height of the valve from the gray ring now? Sorry, I know I'm asking so many questions!

To lower the water level you would lower the float. Get new seal, remove cap, hold a cup over valve and turn on water briefly to flush valve. Install new seal and reinstall cap. Sounds like seal and cap are not seating properly. I was working on toilet a few days ago, wasn't letting water in like it should. I remove cap, flushed valve and reinstalled cap. Seal looked good. Still did not have proper flow. When I remove seal to replace I discovered that the seal had separated from the part that fit on the little pin connected to the lever.

So replace seal.

So after replacing the seal, putting the cap back on properly and adjusting the water level, the toilet WORKS!! Thank you soooooo much Harold! :)

And we thank you for the update. Good luck, Tom