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Discussion Starter #1
Can someone help me understand what these sensors do for the 305. Are they part of ECM system or independant? Thanks.

EFE CONT SWITCH AC DELCO #212-72-THERMAL VACCUM?
CNSTR PURGE SWITCH AC DELCO#212-232-KNOCK SENSOR?
CLNT TEMP SENSOR AC DELCO#213-928-AIR CHARGE TEMP SENSOR?

CNSTR PURGE SWITCH is broke off on manifold, charge temp sensor is broken at base is broken looks like wire that connects to it is not complete?

Have ordered above stuff to give ecm one last try before/if I replace with non ccc items.
Have read up on some ecm info but still learning. Thanks
 

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Ecm

I would recommend that you go to helminc.com, and order the service manual. They have in depth material on the ECM sensors and the emissions system.
 

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no ecm s in 74. but to answer your question all of the sensors and switches connected to the ecm send input to the ecm to alow it to make the engine operate as effieciently as possible in both emissions and milage while improveing driveability
 

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Discussion Starter #5
Sorry folks these are in my 1985 El Camino not the 74 Sprint. I need to get the Helmic manual as suggested, just wanted to know about those particular items. Thanks for your help and thoughts
 

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Sprint, of the sensors you mentioned in your first post, only the Coolant Temp Sensor and knock sensor affect the ECM as far as mileage and running. The others are there for emissions control and to burn off the fumes fro the cannister ( a good thing!).

The temp sensor is the most important one. Without info on the heat of the engine, the system will not go into Closed Loop. The knock sensor is there to retard the ignition if you start to get knock(ping). Otherwise, it is inert to the operation. It is important to have to protect the engine, as you can have knock and not hear it in the vehicle.
 

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HelmInc.com

A little off topic, but I have found that the service manuals are often cheaper from Helm, then what they go for on Ebay. That is usually the way of auctions, people pay more than what something costs new.
 

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helm is the source for original gm shop manuals. everybody elses is third party or worse.helms is who supplies the gm dealers with thier manuals
 

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Discussion Starter #10
Bought manual off ebay, thanks for lead. Also thanks on other info. Will get items replaced and see how the 305 performs now. If they are not attached, what does the ecm do? Thanks
 

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like it was stated, the only one affecting ECM is coolant temp, but might as well replace all the broken ones and have a fully functional emission system
 
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