91 grand wag vac adv and cto... i'm confused..

[Dogs-in-the-back]

OK experts, here's the deal. I was getting no vac signal to the dist, and found the cto wouldn't let and vac pass through to the D port warm or cold, from either 1 or 2 port. No big deal, i'll get a new one. Now comes the confusing part. If i'm reading my vac diagram properly, it shows ported vac into port 1 (low temp) and manifold vac into port 2 (high temp) shouldnt this be the other way around?
Thanks, Jason

WOOF WOOF!!

[Bob Barry]

That would be the correct instructions if this was the high-temp CTO on your thermostat housing. It sends full manifold vacuum whenever the engine temp is above 220ºF to speed up the idle and help cool down the motor.

The connections are the other way around for the yellow CTO screwed into the intake just next to the oil-fill tube, which sends full manifold vacuum below 160ºF.

[Dogs-in-the-back]

Now I get. Thanks for the info, I had no idea that the red CTO in the t-stat housing was set for 220. On my 91, the yello CTO (EGR-CTO on diagram) uses only ports 2 and d. A vacuum line connects S port on psgr side of carb directly to 1 port (low temp??) on the red CTO. This matches 91 diagram. Im assuming there is no manifold vac present on cold start in this config. My 89 uses all 3 ports on yellow cto along with the. non linear valve. This is how it would get manifold vac to dist on a cold start right?

91 is tough to get going when cold, even with a new carb, would giving it manifold vac advance when cold help?
Thanks, Jason.

[Bob Barry]

The setup you describe for the yellow CTO sounds like the setup on my '78, which used a 2-port yellow CTO next to the oil-fill tube for the EGR. On a '91, the EGR vacuum is controlled by a 5-port dual-CTO located on the back of the manifold, and that 3-port yellow CTO should have both manifold and ported vacuum going to it.

Yes, straight manifold vacuum would improve cold-engine driveability.

[Dogs-in-the-back]

Bob,
Thanks for your help, i'm going to get some new vac hose and straighten this thing out. With a little luck it will start tommorow.
Jason