Replace it.
A dual check valve is similar to a double check valve in that it is a mechanical backflow preventer consisting of two independently acting, spring-loaded check valve.
check the indoor water bibs.
If you measure "the applied voltage" (typically, 24 volts) across the coil of the main gas valve, and the valve refuses to open, it will need to be replaced. Before you do, double-check that gas is getting to the valve.The HVAC Veteran
replace only when u get a check engine light. the valve is good for the life of the motor(should be)
There might not be one to replace? On the 2008 3.5L there is none, just a nipple on the valve cover. Double check to make sure.
AIR gap with an AIR Break
you should check egr valve and check for a vacuum leak
Yes, this is part of the job.
There is no difference between check valve and NRV, both are same
Should be a valve on the fuel rail to plug into
A check valve allows for flow in one direction and a gate valve is used for positive shut off and a globe valve is used for throttling
If like my 2000, it is on the left valve cover. it is too cold to go out and double check.