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MDE-4334C Atlas Start-up and Service Manual · April 2008
Hydraulic/Mechanical Components
Pumping Unit
Installing the PCV
To install a PCV, proceed as follows:
Modification of the PCV or failure to correctly install all components of the PCV will
void
any regulating agency recognition applicable to this pump.
IMPORTANT INFORMATION
1
Inspect the valve for damage or excessive wear. Replace the valve, if necessary.
Note: The valve should move in and out of the valve bore freely, with only minor resistance. If
it does not, check for burrs or contamination in the bore or on the valve.
2
Install the PCV in the reverse order of removal (see
3
Apply a thin coat of grease on the cover of the gasket to prevent the gasket from being
damaged during installation.
Note: Replacement of the gasket is recommended if the gasket has not been replaced during
previous service, and is older than six months or shows signs of deterioration.
Service Tips
• PCVs normally fail from excessive wear or sticking.
• Symptoms of failure may be reduced flow rate, reduced pressure, or metering of air with a
dry tank.
• The plug in the cap can be removed and a discharge pressure measurement can be taken,
using a gauge at that point. The gauge will measure the pressure downstream from the
control valve. A stuck valve will result in lower pressure.
Servicing the Bypass/Pressure Relief Valve (PRV)
The PRV functions to prevent excessive pressure from being built up internally within a
pumping unit. Excessive pressure can cause overheating during idling, motor stalling, or
premature motor failure. Low factory pressure settings can cause low flow rate. Relief settings
are set for normally anticipated operation with the unit style, and should not be changed from
factory settings.
• Wear eye protection. Residual pressure and entrapped fuel may still be present
and may drain or spray while removing parts.
• Fire and explosion could result in severe injury or death.
• Test and close the shear valves involved. Shut off power to the unit.
• Remove parts slowly. Collect fuel in approved containers.
• Clean up all spills promptly.
WARNING
