EGR valve test?

[valkster]

Hi, I found a similar question from RandyLL in the past but it did not have a confirmed answer so I am reposting the question. Should the EGR valve on an '83 258 actuate with vacuum applied to the port or does it also require exhaust back pressure? Mine won't move with vac applied alone during bench testing. The test gauge, incidentally, will not maintain vacuum during the test either. It acts like I have broken diaphragm but need others insights. I can manully move he needle without a problem so the unit doesn't seem to be stuck. Thanks as always.

Mark

 

[Rosco1974]

EGR will open with vac alone. You should see the rod move. If its like sucking through an open straw, its dead.

 

[mcmud]

The Positive Back Pressure EGR (standard equipment) will not activate nor hold vacuum with any amount of vacuum being applied until there is adequate back pressure in the exhaust system.

If you've modified the exhaust system in any manner reducing back pressure the EGR has become an ornament.

A simple test would be to clamp a 1" socket into the end of the exhaust pipe and run the no load engine speed to oh say 2500 rpm. A finger touching the diaphragm inside the cage at the back side would reveal if its able to activate.

 

[valkster]

Ok, thanks. Mcmud, have you bench tested one before without a running engine? Would a plate bolted to the mounting surface with regulated air pressure from my compressor work to simulate the back pressure? My Jeep is not in running condition, she is stripped in mid-restoration. If it won't hold vacuum without back pressure, and mine won't, then there is a check valve in the unit that is closed by the back pressure....correct? I have never worked on one like that. Thanks again

Mark

 

[valkster]

Oops, I found a website explaining how the positive back pressure units work...here is a link if anyone is interested.

http://www.agcoauto.com/content/plugins/p2_news/printarticle.php?p2_articleid=207

Thanks,
Mark