LTD Wagon V8-302 5.0L VIN F 2-bbl (1982)
EGR Valve: Description and Operation
Valve Types
Fig. 45 - EGR Valves
There are three types of EGR valves are the poppet type, modulating type and the tapered stem type, Fig. 45.
The poppet type valve, consists of spring loaded diaphragm, and a valve stem and valve operating in an enclosed valve body. At approximately 3
inch Hg of vacuum, the valve begins to open. The valve stem is pulled forward unseating the valve and allowing exhaust gas to flow into the valve
chamber. Venturi vacuum will then pull the gas from the chamber into the air-fuel flow and then into the combustion chambers. Once the valve has
been unseated the only means of limiting exhaust gas flow is the size of the flow restrictor placed in the inlet port of the valve body. The size of the
restrictor will vary according to engine application.
On the modulating type valve, an additional disc has been added to the valve stem below the main valve. The modulating valve operates exactly
like the poppet valve when vacuum is between approximately 3 in Hg and 10.5 in Hg. When vacuum reaches approximately 10.5 inches, the lower
disc (high vacuum flow restrictor) approaches the shoulders of the valve seat and restricts the flow of exhaust gas. The purpose of the modulation
of gas flow is to improve driveability on certain engine models.
The tapered type valve resembles the poppet and modulator types in function, except that the stem portion protrudes below the mounting flange.
NOTE: The EGR valve and vacuum control valve cannot be repaired and must be replaced if damaged.
