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78 620 CAC valve question


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Hello! Just bought a 78 620 and I’m new to the forums. I recently tried to get emissions tested and it failed via the air system check. The guys at the emissions testing facility pointed out two nipples on the bottom of the CAC valve that were not connected to anything. So my question is what are those and where do they connect? I’ve tried looking around but only saw info on the main air lines to the valve. Added a pic to help identify. 

https://imgur.com/tmN2yEc

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tmN2yEc.jpg

 

The CAC (combined air control) adjusts the air from the pump to more accurately control the catalytic converter temperature. My diagram shows both small pipes  join together and then connect to the intake manifold. Inside the rubber hose is a small orifice or reducer to regulate the vacuum signal.   

 

I found an 'air hose to CAC valve'  18716-B9900 dealer number. (very unlikely they will still stock this part) Any proper size hose will do. You'll need a Y so that it connects to both nipples on the CAC.

 

Can you send a picture of the front intake runner. My diagram shows the hose connecting to it and if missing it must have been plugged. Perhaps it is disconnected from the CAC and you can find it and put it back.. 

 

Hope this helps  

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49 minutes ago, datzenmike said:

tmN2yEc.jpg

 

The CAC (combined air control) adjusts the air from the pump to more accurately control the catalytic converter temperature. My diagram shows both small pipes  join together and then connect to the intake manifold. Inside the rubber hose is a small orifice or reducer to regulate the vacuum signal.   

 

I found an 'air hose to CAC valve'  18716-B9900 dealer number. (very unlikely they will still stock this part) Any proper size hose will do. You'll need a Y so that it connects to both nipples on the CAC.

 

Can you send a picture of the front intake runner. My diagram shows the hose connecting to it and if missing it must have been plugged. Perhaps it is disconnected from the CAC and you can find it and put it back.. 

 

Hope this helps  

What exactly is a front intake runner? Not familiar with that term and want to get the pic you your asking for. 

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Found it. Thank you

https://imgur.com/a/Aj5ny35

 

 But the two lines coming off of it are connect to CAC valve and the fuel shut off vacuum switch.

https://imgur.com/a/msBScS1

 

Found this diagram and in the bottom right corner is the CAC. The hose looks like it is just routed into it self. Could that be correct?

https://imgur.com/a/XTmZt2x

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There should be two hoses on the manifold, below.

 

3bp1cis.jpg

 

One from the CAC and one from the fuel shutoff control go to the intake below. Not sure what the red circle on the right is. Maybe a T fitting should be there with a hose down to the second nipple on the CAC?

 

BTj8dl0.jpg

 

 

This doesn't show the two hoses to the intake.  

 

YusSjeg.jpg

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Yes, that is correct. There are to hose connection on the manifold fitting. The circle on the right is the connection from the manifold fitting to the  fuel shutoff control. There isnt a T there. I think someone just put a fitting there to extend the hose length instead of getting a correct length hose. In the shop manual I got with the truck it shows those connections but nothing about the two connections on the bottom of the CAC. 

https://imgur.com/a/XrMuQAC

https://imgur.com/a/COgb594

 

 

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