Also, what are the cheapest fuels that are capable of reaching the critical height?
Get some Sevin dust and put it in a plastic ketchup bottle (the kind with a small hole). At night when all of them are back in the nest go out quietly in the dark and blow the dust into the hole. Attach a straw to the hole in the bottle if you have toMcD straws fit just fine. By morning all should be dead. Liquid sprays have an instant knock-down but if the nest is to the sides of the hole or above the hole the poison will not hit them. The dust poofs in there in all directions.
it could be a few things. you could have rolled a seal and thus letting fluid by-pass or you could have a fluid lock from air in the system try bleeding the lines before taking it back apart.
