Vacuum lines
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MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Vacuum lines
Hi all, my '73 400 with a motorcraft 2100 has a strange vacuum setup...I haven't been able to figure out what it does nor have I been able to identify it with any emmisions control listed in Chilton's. Here goes:
There's a vacuum line coming off the front of the carb. It goes to a ported vacuum switch in a coolant pipe. The other line off the switch then goes to a little solenoid-looking thing that has two wires going to it. The other line off that solenoid then goes to the EGR valve. There is a T in the line from the solenoid to the EGR valve in which another line is hooked, and that line seems to be going down towards the transmission.
There's another vacuum line going from the side of the carb under the choke housing, and that line goes to the distributor vacuum advance (doesn't seem right to me). That port doesn't seem to have much vacuum coming from it, I can't feel much whether the carb's at idle or full throttle.
Does this stuff ring a bell to anyone? Or is it not hooked up right? Thanks.
There's a vacuum line coming off the front of the carb. It goes to a ported vacuum switch in a coolant pipe. The other line off the switch then goes to a little solenoid-looking thing that has two wires going to it. The other line off that solenoid then goes to the EGR valve. There is a T in the line from the solenoid to the EGR valve in which another line is hooked, and that line seems to be going down towards the transmission.
There's another vacuum line going from the side of the carb under the choke housing, and that line goes to the distributor vacuum advance (doesn't seem right to me). That port doesn't seem to have much vacuum coming from it, I can't feel much whether the carb's at idle or full throttle.
Does this stuff ring a bell to anyone? Or is it not hooked up right? Thanks.
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
Everything sounds right to me. Maximum vacuum on the carb spark port is only about 12 in/Hg, and it hits that with the throttle open just 10-20 degrees. Vacuum on the spark port at WOT is considerably lower than its maximum (maybe 7-10 in/Hg).
Trace the line going down from the "T" to the EGR valve and see where it goes.
Trace the line going down from the "T" to the EGR valve and see where it goes.
Senior User
Joined: Jan 2003
Posts: 176
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From: Addison,Texas
This is a 400 in a Ranchero/Torino/Montego, right? (Or is it a regular Ford/Mercury?)
That beastie is a High Speed EGR Modulator Sub-system. The wires run to a speed sensor that causes the solenoid to cut off vacuum to the EGR valve circuit when speed exceed 64 MPH. It does tee and connect to the DAD (side port, not center port) on the transmission. It's supposed to run through a loop connector first.
The other side (spark port, under the choke) is supposed to have some extra bits, but it does eventually run to the advance can.
ash
['Is this the one that doesn't run right cold?']
That beastie is a High Speed EGR Modulator Sub-system. The wires run to a speed sensor that causes the solenoid to cut off vacuum to the EGR valve circuit when speed exceed 64 MPH. It does tee and connect to the DAD (side port, not center port) on the transmission. It's supposed to run through a loop connector first.
The other side (spark port, under the choke) is supposed to have some extra bits, but it does eventually run to the advance can.
ash
['Is this the one that doesn't run right cold?']
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MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Thanks for your replies.
Ash, thanks for your explanation, and if there is a site somewhere where I can learn more please let me know.
This thing is wired up just like electronic spark control--there is an ambient temperature sensor, a vacuum solenoid, and a sensor on the speedometer cable, all wired into an electronic amplifier under the dash. But vacuum-wise it is hooked up to EGR. How is this supposed to help emmissions?
What is the DAD port on the transmission...and why does this controlled vacuum run to it?
This 400 is in a Galaxie 500. Yeah, it is the one that doesn't run right when cold...I did get it better though-I brought the timing to around 8 degrees BTDC and it hasn't backfired since. However, no matter how much I mess with the choke it still seems a bit rough for the first couple minutes when cold.
Thanks guys
Ash, thanks for your explanation, and if there is a site somewhere where I can learn more please let me know.
This thing is wired up just like electronic spark control--there is an ambient temperature sensor, a vacuum solenoid, and a sensor on the speedometer cable, all wired into an electronic amplifier under the dash. But vacuum-wise it is hooked up to EGR. How is this supposed to help emmissions?
What is the DAD port on the transmission...and why does this controlled vacuum run to it?
This 400 is in a Galaxie 500. Yeah, it is the one that doesn't run right when cold...I did get it better though-I brought the timing to around 8 degrees BTDC and it hasn't backfired since. However, no matter how much I mess with the choke it still seems a bit rough for the first couple minutes when cold.
Thanks guys
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