What signals the egr to open? I have never understood what controls it. One of life's mysterie to me
74Plb

 

ECU

 

Also controlled by exhaust back pressure. The transducer just upstream of the valve, has a diaphragm in it too. With vacuum applied to the transducer (from the solenoid), low exh backpressure vents the vacuum keeping the EGR closed. High exh backpressure pushes up on the diaphragm, blocks the vent, so the vacuum draws from the valve, opening the valve. Once the backpressure reduces, the spring in the transducer pushes the diaphragm back, unseats the vent and vents vacuum the atmosphere.

The ECU controls the EGR solenoid which, in turn, pulls the vacuum to the transducer or vents it. So the ECU determines when to draw or vent vacuum to the EGR itself, via the solenoid. Then, exh backpressure through the transducer, will seat/unseat the valve.




The guts of the transducer. On the left, is the bottom half, then the diaphragm, then the upper half with spring. (yes, that's it!)

 

Wondering if you could use the transducer from the 88 dodge d150 or the 90 dodge dakota. My EGR valve seems to be fine. My transducer on the other hand is giving me a hassle. The spring in the transducer has deteriorated, but the diaphragm is ok. Wonder if the spring could be replaced in the transducer. In any case I need to fix my 1990 XJ before the end of Nov or I'll be walking.

 

Does anyone want to purchase EGR valves and/or transducers?

 

Most definitely

 

Had a look at them on RA. I think they would work. Three ports just like the XJ one. Good thing RA sells just the transducer.

 

Morning, not familiar with RA who are they?

 

RA = Rock Auto rockauto.com

 

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