Nissan Repair: 1986 300zx, excessive blowby, vacuum gauge

Question
I just got this non turbo car,it failed emission test from the last owner.I'm checking egr system ,diaphragm check is good.I dont't have any vacuum to the inlet of the solenoid valve. How does this system work?

              Thanks, Tom

Answer
Tom,

System runs from ported vacuum.  That is, there is no vacuum to the EGR at idle.  Also, the ported vacuum is controlled via a temperature controlled vacuum switch.  The switch will not allow the EGR to perform unless the engine is at operating temperature.  So, with the engine warmed up and running down the road it will open the EGR valve.  To check the system, on the EGR side of the control valve, run the engine up to around 1500 RPM and see if the valve gets vacuum.  You can use a vacuum gauge to monitor this.  Usually, if the hoses are intact, you will get vacuum.  And, if the EGR is working but you are failing emissions check it means the pathways in the system are carboned up.  Other causes for failing emissions are leaky injectors, or excessive blowby.  That is, the engine burns so much oil that the converter cannot control it and the converter goes.  If you let me know what the readings were from the test I could be more specific.