Originally Posted by
show me the money
you want the pilot flame to contact the powerpile, but not the thermocouple.
The small thermocouple should not have flame contact! That device is your oxygen depletion sensor, the flame is close but not touching, when the oxygen is low the pilot flame with shrink ever so little allowing the thermocouple to turn the pilot out, stoping the ignition process.
If the pilot stays lit the thermocouple is ok.
The job of the powerpile is to power the gas valve open.
First with out any way to measure the DC signal of the powerpile, all you can do is check the electrical connections, which must be tight, and clean the pilot assembly.
If the pilot flame is strong and the DC signal is within limits, you may have a mulitude of possiblities wrong. For example, gas pressure problem, when the gas valve opens the pressure drops shrinking the pilot flame. Check the gas pressure on both sides of the gas valve. The gas valve may be going bad. The gas pressure maybe to high causing over firing, and shuting off due to open high limit. Check the chimney for obstuctions, openings, seems like dumb advice as most chimneys have tight capping, but that doesn't keep wasps out. I had a totally blocked chimney from paper wasps.
Assuming you are not as stupid as most DIY'ers are thought to be by contactors I assume you know that fuel gas is explosive and flamable.
You could aquire a simple tool set of a DC ampmeter/voltmeter, and a gas simple dial type gas pressure gauge for under 50 bucks.