My pump will not come on.

What sort of nest ... bees nest, wasp nest ..........

Go to a hardware store and get Wasp Killer. This stuff shoots in a stream and really kills on contact. Shoot it in there and keep shooting and you should be ok. Shoot it in a safe area to see the stream that I'm talking about.
Gary

I had a similar problem. Turns out I had left the hose disconnected and some sort of wasp built a paper type nest inside the washer tube that the hose connects to. I had to take the pump off and take apart and then cleaned it out with a screw driver. Not too easy to do but finally got it clean. Same thing happened with the hose.

So, if you haven't used it for awhile, check that there is no blockage in the hose or pump tubes. You might be able to blow it out with an air compressor.

A couple of things, what makes the engine change tone and revs is pressure, depending on the age, it may have excessive calcium build up in the pump, there may have also been a build up of crud or a wasps nest in the end of the hose when you connected and is now in the actual pump, you can remove the base and flush the sytem, hope this helps the problem, good luck.

Howdy, you can use a septic tank enzymatic cleaner to dissolve the paper of the nests. If you mean there are mud type nests you must soak them for a long while then they will rinse out. Hope this helps. Happy zymurgy:)

usually this happens whrn the fan motor burns out...have you seen wasps bc wasps get in through the outside vent and build up nests..this is a common problem

Going to have to remove cover on roof. Will need to remove all Philips screws around near bottom. If you have/had wasps in there, take a real good look before you pull cover of, and try to do it on a cool, cloudy day, or at dusk, just in case there's more there. If you do it early in the morning, watch for slippery roof. Take a can of wasp/hornet blaster with you as it's not unusual to find more nests under that cover. Been there, done that, many times. Good Luck, keep me posted on results.

You will need to pull your tray from the heater to check for Wasp nests or other problems. You need to be careful with the wasps if you smoke them out be very careful not to burn any wires or components on the heater. If you have access to a co2 fire extinguisher the cold and lack of oxigen will hold them at bay for a few minutes. Back to the heater...
Your dead on about the gas build up. This comes from something blocking your pilot so that your burner flame isn't lighting on the burner that is connected to the pilot. If you have a wasp nest on the burner this will do be the problem. I want to think that when the heater fires this would fix that problem. What is more common is on the gas pipe that feeds the burners you have a gas orface for each burner. Small spiders will sometimes build webs that resemble lint inside the orfaces. You can clean these with a bent wire.Other than that anything blocking the burners will be evedent. I hope this helps, good luck.

Yes! It is dangerous. The pressure switch is malfunctioning and allowing the heater to remain on when the pump shuts off. You should not use the unit until a qualified repair tech can look at the unit. There is only one other set of limit switches that are turning your burners off before the boiling water bursts the tube bundle so if they fail to react in time, you'll burst the heater, cause expensive damage and risk injury.