When checking inlet and manifold pressure, there are many different tools that will do the job. The manometer is one of the least expensive and also one of the best because it allows you to calibrate it every time you use it, ensuring an accurate reading. The manometer is a U shaped tube filled with liquid which has a valve or stopper at the top of each riser. In between these risers is an adjustable scale that is measured in inches which allows calibration of the manometer.

Another quick check you can carry out is the system resistance check. This will verify whether your control circuit has too much resistance in it. 

There are two instances where you will measure resistance when checking a valve for faulty main burner operation.