The EGR valve is located on the intake manifold next to the carburetor. In most cases, malfunctions in the exhaust system are due to jamming or corrosion of the EGR valve.
On a cold engine, manually move the diaphragm from below the EGR valve. By applying moderate pressure, you must move the diaphragm up and down within the body.
If the diaphragm does not move, or only moves when a lot of force is applied, replace the EGR valve. If you are not sure if the valve is working, compare the free movement of your EGR valve with the movement of the new valve.