Vacuum line help
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Vacuum line help
I've recently purchased an '86 F150 w/ a carbed 300. After a quick tune up, carb rebuild, an a lot of reading in my repair manual I've realized that this truck was stripped down to the bare essentials. Most of the electrical is just sort of hanging out unplugged and the only vacuum line that isn't capped off is for the brakes.
The truck runs fine now as far as I can tell and I can live without knowing where all that electrical should be going. I do however need to know where my vacuum lines connect, but I don't have a vacuum diagram under the hood.
First, there are three lines coming off the carb. One has EGR on it so I'm gonna assume it connects directly to my EGR valve. The next has the letters DIS next to it. My first thought is distributor, but where does a vacuum line connect? Then there's the last line that isn't labeled so now I'm completely lost.
Second, as I'm reading I find something about a bi-metal sensor? and heat rise pipe?. The pipe is gone, but there's this little flap-I forget the name- that sits inside the air cleaner housing to redirect warmer air from off the exhaust manifold. With the bi-metal sensor and attachment leading to the flapping thing there are three available vacuum line attachments. How do these pieces attach to the vacuum lines?
Any help whatsoever would be greatly appreciated.
The truck runs fine now as far as I can tell and I can live without knowing where all that electrical should be going. I do however need to know where my vacuum lines connect, but I don't have a vacuum diagram under the hood.
First, there are three lines coming off the carb. One has EGR on it so I'm gonna assume it connects directly to my EGR valve. The next has the letters DIS next to it. My first thought is distributor, but where does a vacuum line connect? Then there's the last line that isn't labeled so now I'm completely lost.
Second, as I'm reading I find something about a bi-metal sensor? and heat rise pipe?. The pipe is gone, but there's this little flap-I forget the name- that sits inside the air cleaner housing to redirect warmer air from off the exhaust manifold. With the bi-metal sensor and attachment leading to the flapping thing there are three available vacuum line attachments. How do these pieces attach to the vacuum lines?
Any help whatsoever would be greatly appreciated.
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Joined: Aug 2003
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From: Who cares?
The DIS would be for the vacuum advance on the distributor. The vacuum advance is attached to the front of the distributor just under the cap. It is round and has a single vacuum attachment to which the tube is connected. You should really notice if it is disconnected. Your response to acceleration would suck without it. You should also have one or two ported vacuum switches threaded into the water jacket. These control vacuum based on the temperature of the engine. Most every vacuum operated thing on the engine comes off these switches because they determine what is on or off. You have to know what is normally open and what is normally closed on the switches to start to understand what vacuum line goes where and when the item needs to be active or inactive. Without the diagram it can be very difficult.
On my truck there is a valve that closes the left exhaust forcing the hot gases through the head into a crossover pipe, the EGR and then through the right exhaust. When the PVS heats up, the ported vacuum switch shifts and drops the vacuum to the valve which has a spring to open. So that is one of the lines that goes from the normally open (active) ported vacuum switch. The heat riser from the right side exhaust manifold is a flexible piece of tubing (like a dryer vent) that allows the intake to get heated air from around the manifold. There should be a shroud around the manifold to which you connect one end of the vent tubing and the other goes to the bottom of the air intake horn. The tubing is available at the auto parts store. The valve in the intake is controlled by temp and opens to fresh air when it gets hot enough. I forget what the little thing in the intake is called that has a vacuum line attached. I can't remember what it is for either. Also there should be a vacuum line going to a distribution line mounted to the firewall just under the hood gasket. This line takes manifold vacuum to operate your Fresh air/Recycled air setting for your AC, cruise control, AC blend door and anything else that is vacuum controlled. Then finally the other lines are for all the other emission controls. The library in my town has old shop manuals for trucks, maybe yours does also. You can't usually check them out but you can make copies. So you may be able to find the missing vacuum routing diagram in one. The problem I have with the diagram is deciphering the code they use. I have one connection labeled S and have no idea what it is for. Hope this helps you.
On my truck there is a valve that closes the left exhaust forcing the hot gases through the head into a crossover pipe, the EGR and then through the right exhaust. When the PVS heats up, the ported vacuum switch shifts and drops the vacuum to the valve which has a spring to open. So that is one of the lines that goes from the normally open (active) ported vacuum switch. The heat riser from the right side exhaust manifold is a flexible piece of tubing (like a dryer vent) that allows the intake to get heated air from around the manifold. There should be a shroud around the manifold to which you connect one end of the vent tubing and the other goes to the bottom of the air intake horn. The tubing is available at the auto parts store. The valve in the intake is controlled by temp and opens to fresh air when it gets hot enough. I forget what the little thing in the intake is called that has a vacuum line attached. I can't remember what it is for either. Also there should be a vacuum line going to a distribution line mounted to the firewall just under the hood gasket. This line takes manifold vacuum to operate your Fresh air/Recycled air setting for your AC, cruise control, AC blend door and anything else that is vacuum controlled. Then finally the other lines are for all the other emission controls. The library in my town has old shop manuals for trucks, maybe yours does also. You can't usually check them out but you can make copies. So you may be able to find the missing vacuum routing diagram in one. The problem I have with the diagram is deciphering the code they use. I have one connection labeled S and have no idea what it is for. Hope this helps you.
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Joined: Jan 2001
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From: Virginia
Being your 300 is a later model, I bet it had the computerized carb system on it. If your distributor does not have a place for a vacuum line (sounds like it doesn't), then you are going to need to change the distributor out for one that does.
The computer controlled all the timing in the computer style distributor. Now all this stuff is disconnected, you have no timing control.
This computer system your truck used to have is a pain to work on. Someone has taken a bunch of stuff off, so you should probably just continue what they started, and get it running even better. You are going to need an older duraspark II distributor that has the vacuum line and the advance weights inside, and the module to run it. You could also check out some aftermarket one wire distributors too.
The computer controlled all the timing in the computer style distributor. Now all this stuff is disconnected, you have no timing control.
This computer system your truck used to have is a pain to work on. Someone has taken a bunch of stuff off, so you should probably just continue what they started, and get it running even better. You are going to need an older duraspark II distributor that has the vacuum line and the advance weights inside, and the module to run it. You could also check out some aftermarket one wire distributors too.
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Joined: Jan 2007
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From: Martinsburg, WV
