The pilot light goes out when i release the pilot knob. I have a 35 c pitco frialator

Replace the thermocouple.

It can take a up to a minute for the thermocouple to get hot enough to latch, the flame is to low, not in the position to hit the thermocouple or just bad. Some valves need to be turned to the ON position after lighting the pilot and waiting for the thermocouple to get hot. Sometimes the nut that holds the tube to the valve comes loose and requires being tightened but not to tight.

Hi there.
you can view a picture of gas valve knob position when you visit http://www.pitco.com
Regards.

Try first to clean the thermopile. If it has accumulated soot/ carbon, it will not sense enough heat from the pilot flame to generate small amount of electricity to energize the pilot valve and main valve of gas valve.

Check if the unit receives the right amount of fuel as stated on its nameplate, if it does, check all wires for loose connections, Milli volt wont pass on loose wiring. If this does not correct the problem, you have to replace the gas valve, the main valve coil may be shorted that's why the pilot is shut when main valve is energized.

Check and clean the thermopile, it is the cylindrical piece of metal standing behind the pilot assembly.Try also to tighten its wiring connections to the gas valve and high limit.If it does not correct the problem, replace the thermopile.

Pilot assembly is located between the two middle burners, this is where the pilot is lighted. You have to turn the gas valve knob to pilot position then push it while lighting the pilot assembly.

Pilot should hold 30 to 45 seconds after igniting when gas valve knob is released. If there is 500 millivolts across the pilot terminals and still the piolot wont hold, you have to replace the gas valve.

Try to spray wd40 on knob.
If spraying wd40 doesn't work, you have to replace the gas valve.

If you have a pitco 35 fryer, all you need to do is have gas connected and turned on, rotate the know on the gas valve to the pilot position, depress the knob, while holding the knob down light the pilot, normally located in between the burner tubes in the middle of the front of the fryer, hold the knob for 60 seconds, when you release the pilot should remain on. If it does rotate the pilot know to the "on" position, from this point the thermostat should control the fryer. If your pilot does not stat lit, press the red button on the hi-limit to reset it, it could be tripped and this would cause the pilot to not hold. Hope this is helpful.