Hi my "new to me" 93' S83p the four post vacuum manifold that is thermostatic controlled is broken off. (Not sure what those lines are all controlling just yet) It has me wondering if anyone has stripped the emissions controlling vacuum lines and just kept the essentials for the engine a 4 wheel drive. If so would they mind sharing pictures of how the routed the lines?
There is a thread with the vacuum diagrams for the stock setup. Search for 83P vacuum diagram. Looking at it, unless you change out the carb, you’re kind of stuck. There are lines from the valve cover, and the fuel pump which run to manifold vacuum. These both need to stay, the one to the fuel pump, is the only way it gets oiled. The ones from the thermostatic vacuum valve, control the air box switching, and an enrichment circuit on the carburetor. You could probably get rid of the one for the air box switching. but, the truck won’t run very well without the enrichment circuit when the engine is cold.
Thanks for the replies! I was having trouble finding a vac diagram with descriptions in English. Thanks shogun, that thread looks to have the most helpful diagram I've seen for these vac lines.
When we switched over to a manual choked carb, we were able to plug all the ports on the four post 'tree' by the fuel pump. We connected any of the others off that branch that were still needed to other manifold ports.
If you have a way to switch the air feed from summer to winter there shouldn’t be any need for the thermostatic vacuum switch. The S80 and S81 were manual, and had a lever under the right hand seat to switch it. Depending on where you are, you can ice up the throat of the carb on a tiny truck.