What is this Vavle for
 

Hello,

What does this valve do, and where should the vacuum line be routed? It's capped off as you can see. It's on bolted toward the back of the intake Manifold. This is a 250 Inline 6.

[IMG]https://i.imgur.com/fQPfS0W.png[/IMG]

Re: What is this Vavle for
 

Egr valve, allows exhaust into the intake to reduce emissions.

Re: What is this Vavle for
 

So I would loop a vacuum like back to the Carb somewhere? It's not a big line, maybe 1/4".

Re: What is this Vavle for
 

You would want to run a line to a ported vacuum source.

Re: What is this Vavle for
 

If the emission sticker is still on the radiator support, it will tell you where the vacuum line goes. Sometimes they route thru a temp sensor on the t-stat housing.

Otherwise post up the year and maybe someone will post a pic of a sticker.

Re: What is this Vavle for
 

Oh yeah, its a 1978 GMC C15. I don't have the sticker. There isn't a temp sensor on the housing. There are two blocked off plugs. They're painted blue to match the Thermostat Housing. It's possible it was removed.

Re: What is this Vavle for
 

Do they have emission testing in your part of the state for this year of truck?

Re: What is this Vavle for
 

A lot of people just bypass it

Re: What is this Vavle for
 

Maricopa county (Greater Phoenix Area) actually does emissions testing. Looks like the P.O. bypassed it by plugging it off. I'd like to attempt an emissions test soon. I'll probably need to connect it for testing purposes.