Question about Vacuum Line Routing?

[1-ton]

I have a vacuum controlled HVAC air box in my 1991 Chevy V3500 that I need to connect a vacuum line source to, in order to make it function properly. The four parts of the vacuum system I need to connect are the intake manifold vacuum source, vacuum reservoir, HVAC air box diaphragm, and (I think) a one-way check valve, in order to make my HVAC vacuum controlled air box function properly. I am not sure in what order I need to connect everything to my intake manifold vacuum source. My question is how do I connect everything together, and in what order to make it work?

 

[1-ton]

ttt

 

[454Sub]

IIRC it's intake to 1 way valve, and one side of valve goes to pod and other side of it goes to vacuum doors. You want the pod and doors to be on the side that holds the vacuum.

 

[1-ton]

Thanks for the reply. Since this subject is kind of "in the weeds", it is hard to get a reply on it. I have the vacuum line set the way you described it now, but there was a vacuum leak in this configuration, so I was not sure if I had correct. I may have the vacuum check valve in the wrong way, or it is defective because I used a 25-year old one I had laying around.

 

[blazer74]

Without the under hood factory decal it's hard to find the correct routing.
Even the factory services manuals can let u down

 

[1-ton]

Without the under hood factory decal it's hard to find the correct routing.
Even the factory services manuals can let u down

I have the emission vacuum line routing sticker on my trucks air filter box. It is the accessory vacuum line diagram I am dealing with right now, and info on that is not common to come by.

 

[454Sub]

Check and make sure it's the correct T. Both sides of it should hold vacuum so when the engine is revved up or off the vacuum isn't released. It should still go pssssh when the truck is off and the controls are moved as the vacuum is released from the pod.

 

[1-ton]

Check and make sure it's the correct T. Both sides of it should hold vacuum so when the engine is revved up or off the vacuum isn't released. It should still go pssssh when the truck is off and the controls are moved as the vacuum is released from the pod.

For some reason the whole thing has a vacuum leak somewhere. I do not know if it is a dry rotted vacuum check valve diaphragm or what. The vacuum tubing is all new. I am going to get a new check valve, and try it both ways to see if I can get it to work.

 

[454Sub]

Is the pod cracked?

 

[1-ton]

Is the pod cracked?

The case is not cracked, but the rubber diaphragm seems to not be sealing very well because it is old the rubber is probably dry rotted. When I hooked up this whole thing it caused my engine to run like it had a vacuum leak. After I removed it and put a vacuum cap on the intake manifold vacuum port the engine ran good. I going to get a new vacuum check valve (they are not very expensive) and try the whole thing over again.

 

[454Sub]

You have it narrowed down. Now simply just work up stream. Isolating the system one piece at a time until you find the leak.