Starliner Posted May 8, 2020 Share Posted May 8, 2020 I have read the great Documents on the Vac Systems that Gary has posted. I still need help as I see some redundancy to my system. Feel free to laugh at the color coding. Red, (top port), goes to a multi T connector which goes to vac at carb base. yellow, (middle), goes to vac advance green, (bottom one), gets more complicated but it loops back to the same T as the red. I will stop there for now, it already sounds ridiculous. Thanks Link to comment Share on other sites More sharing options...
Starliner Posted May 8, 2020 Author Share Posted May 8, 2020 This is the more complicated mess. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted May 8, 2020 Share Posted May 8, 2020 Color coding is great! The little Tee in the yellow line is a vacuum restriction. (coming from the green side) The distributor advance gets restricted vacuum until the thermal vacuum switch senses something above about 225*. At that point it switches to full manifold vacuum which pulls in a little more timing and steps up the idle. Increasing idle speed causes the fan and water pump to turn quicker and aids cooling if you're stuck in a hot traffic jam or something. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted May 8, 2020 Share Posted May 8, 2020 This is the more complicated mess. What do you want to do with the other thermal vacuum valve? Return it to functionality? Link to comment Share on other sites More sharing options...
Starliner Posted May 8, 2020 Author Share Posted May 8, 2020 Color coding is great! The little Tee in the yellow line is a vacuum restriction. (coming from the green side) The distributor advance gets restricted vacuum until the thermal vacuum switch senses something above about 225*. At that point it switches to full manifold vacuum which pulls in a little more timing and steps up the idle. Increasing idle speed causes the fan and water pump to turn quicker and aids cooling if you're stuck in a hot traffic jam or something. Jim as far as I can see it hasnt hurt anything to cap it off. I took the smog pump off, and capped the egr but didnt remove it, just capped the vac line. On the valve with the hoses, i have vacuume from carb base attached to the top and bottom connections, with the vac advance in the middle. That has to be wrong. I wish I could post a video to walk through it but I will draw a diagram of the current condition and post it tomorrow. Thanks Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted May 8, 2020 Share Posted May 8, 2020 Jim as far as I can see it hasnt hurt anything to cap it off. I took the smog pump off, and capped the egr but didnt remove it, just capped the vac line. On the valve with the hoses, i have vacuume from carb base attached to the top and bottom connections, with the vac advance in the middle. That has to be wrong. I wish I could post a video to walk through it but I will draw a diagram of the current condition and post it tomorrow. Thanks No, that's right for an '84. Later trucks had 3 port valves, but the function is the same. You have restricted flow until the wax pellet in the valve pushes the port open and then full manifold vacuum is applied. It's ALL coming from manifold vacuum. (or base of the carb) Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted May 8, 2020 Share Posted May 8, 2020 Jim as far as I can see it hasnt hurt anything to cap it off. I took the smog pump off, and capped the egr but didnt remove it, just capped the vac line. On the valve with the hoses, i have vacuume from carb base attached to the top and bottom connections, with the vac advance in the middle. That has to be wrong. I wish I could post a video to walk through it but I will draw a diagram of the current condition and post it tomorrow. Thanks Does your truck still have an emissions vacuum routing diagram on the radiator support or DS valve cover. Can you take a pic showing the diagram and the calibration code? Link to comment Share on other sites More sharing options...
Starliner Posted May 8, 2020 Author Share Posted May 8, 2020 Does your truck still have an emissions vacuum routing diagram on the radiator support or DS valve cover. Can you take a pic showing the diagram and the calibration code? Link to comment Share on other sites More sharing options...
Starliner Posted May 8, 2020 Author Share Posted May 8, 2020 Link to comment Share on other sites More sharing options...
Starliner Posted May 8, 2020 Author Share Posted May 8, 2020 What are the odds that I could find a vehicle which has spend 34 years on So. Cal. would be non-cat? Link to comment Share on other sites More sharing options...
Recommended Posts