The reasons for the insufficient pressure of Roots blower may be as follows:

1. The intake temperature is too high: During the working process of the blower, if the intake temperature is too high, the gas density will become smaller, which will affect the pressure output of the blower.

2. Gear wear: The compression process of Roots blower is completed by transferring power through the gear, if the gear wear is serious, it will lead to gas leakage, thereby reducing the pressure.

3. Poor seal: If the seal of the blower is aging or damaged, it will lead to gas leakage and reduce pressure output.

4. Rotor clearance is too large: the rotor clearance of the Roots blower plays an important role in the pressure output, if the rotor clearance is too large, it will also lead to gas leakage and reduce the pressure.

5. Excessive intake resistance: If the intake pipe of the blower is blocked or the resistance is large, it will lead to poor intake and insufficient pressure.

Please note that these are just some of the possible reasons, and the specific situation depends on the actual situation