Topic: Faulty EGR?
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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I’m going through my emission system on a 78 replacing collapsed and rotted vacuum lines. I’m also checking various components with my mityvac as I go along. I need a sanity check here, shouldn’t I be able to apply vacuum and hold it on the EGR and air pump diverter valves? Neither will hold a vacuum.
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Some EGR valves are hard to test with a vac. pump, as they need some exhaust backpressure to seal. These are called positive backpressure types, while the others are negative.
Don't know if 78would have that type, just putting the info out there. To test this type of EGR, you have to provide some form of pressure on the end of the valve that opens.
Also, most EGR valves are "bleed" types. They have a bleed-off set-up, so they never really hold vac., but they will open the valve, and then slowly bleed off.(while testing)
The AIR diverter valve should hold, I think, depending on which side you are applying vac. to.
Don't know if 78would have that type, just putting the info out there. To test this type of EGR, you have to provide some form of pressure on the end of the valve that opens.
Also, most EGR valves are "bleed" types. They have a bleed-off set-up, so they never really hold vac., but they will open the valve, and then slowly bleed off.(while testing)
The AIR diverter valve should hold, I think, depending on which side you are applying vac. to.
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Positive back pressure EGR it is.. Blow a light stream of air into the exhaust in port while applying vacuum and it will open. That's $50 I don't need to spend. The A.I.R diverter valve is a different story.
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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