72 TCS System/Solenoid testing
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72 TCS System/Solenoid testing
Hello, I just finished re-installing the original carb on my 72 with manual trans car. I have hooked back up the original tcs system (It had been by-passed by the previous owner), and I am wondering if there is a way to "bench test" the system. The solenoid is in the closed position (no vacuum to dist) normally, and I understand that the solenoid should open when the engine is warm and the trans is in 3-4 gear. Is there a way to test this with one person (ie I cannot have the car running and in 4th gear and inspect the solenoid)? Any ideas? Thank You
Safety Car
Joined: Apr 2000
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From: Wichita KS
Hello, I just finished re-installing the original carb on my 72 with manual trans car. I have hooked back up the original tcs system (It had been by-passed by the previous owner), and I am wondering if there is a way to "bench test" the system. The solenoid is in the closed position (no vacuum to dist) normally, and I understand that the solenoid should open when the engine is warm and the trans is in 3-4 gear. Is there a way to test this with one person (ie I cannot have the car running and in 4th gear and inspect the solenoid)? Any ideas? Thank You
To test when the engine is idling and at normal operating temperature unplug the vacuum advance line from the distributor. If the TCS is working properly there should be no change in the RPMs since vacuum advance is blocked at all times except:
Engine temp is below 180 or above 230
First 20 seconds after startup
Transmission is in 4th gear
As mentioned in the above post, you can connect a T connector to the vacuum advance line and run a length of hose into the passenger compartment with a vacuum gauge on the end then shift into 4th gear (keeping your foot on the clutch) and watch for a change in the vacuum gauge from none to vacuum present.
You should also notice a distinct change in engine rpms.
cc
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Joined: Apr 2000
Posts: 3,802
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From: Wichita KS
I'm not sure why you want to enable the TCS system. It is intended to raise the engine temperature by blocking vacuum advance in order to lower emissions. A feat it fails at miserably. Lowering emissions that is. It definitely blocks vacuum advance.
You are essentially purposely keeping your engine in a retarded state while increasing the load on it.
cc
You are essentially purposely keeping your engine in a retarded state while increasing the load on it.
cc
Last edited by CCrane65; Aug 24, 2009 at 06:34 PM.
Racer
Joined: Jul 2007
Posts: 430
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From: Florida
My '72 Lt-1 had the same system. You can take it for a test ride and actually hear when the vacuum advance is allowed to the distributor, after a 23 second delay in 4th gear. You should also have advance at idle before the engine warms up, less than 82 degrees (if you disconnect the hose to the advance the RPM should drop).
There's an excellent description of the system in the Service Manual, page 6T-7.
I'm sure others can elaborate,
Good Luck, Chris
There's an excellent description of the system in the Service Manual, page 6T-7.
I'm sure others can elaborate,
Good Luck, Chris
Thread Starter
Advanced
Joined: Feb 2008
Posts: 60
Likes: 0
I'm not sure why you want to enable the TCS system. It is intended to raise the engine temperature by blocking vacuum advance in order to lower emissions. A feat it fails at miserably. Lowering emissions that is. It definitely blocks vacuum advance.
You are essentially purposely keeping your engine in a retarded state while increasing the load on it.
cc
You are essentially purposely keeping your engine in a retarded state while increasing the load on it.
cc
Thread Starter
Advanced
Joined: Feb 2008
Posts: 60
Likes: 0
My '72 Lt-1 had the same system. You can take it for a test ride and actually hear when the vacuum advance is allowed to the distributor, after a 23 second delay in 4th gear. You should also have advance at idle before the engine warms up, less than 82 degrees (if you disconnect the hose to the advance the RPM should drop).
There's an excellent description of the system in the Service Manual, page 6T-7.
I'm sure others can elaborate,
Good Luck, Chris
There's an excellent description of the system in the Service Manual, page 6T-7.
I'm sure others can elaborate,
Good Luck, Chris
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
cc
Sorry, I had that backwards. It's correct for a big block now according to the service manual. Small blocks only check for above 82 degrees.
Last edited by CCrane65; Aug 25, 2009 at 11:51 AM.
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Racer
Joined: Jul 2007
Posts: 430
Likes: 7
From: Florida
On a cold engine the vacuum advance solenoid should be energized (open, allowing vacuum), if not - ground the wire from the cold terminal of the temperature switch. If solenoid energizes, replace the temperature sending unit.
You could also have a bad vacuum advance. Bypass your solenoid and plug it into the port on the carb. If you get advance it's working.
If both these tests are good, it sounds like you have a bad TCS solenoid. But get the service manual, it steps you through the entire process.
Chris
You could also have a bad vacuum advance. Bypass your solenoid and plug it into the port on the carb. If you get advance it's working.
If both these tests are good, it sounds like you have a bad TCS solenoid. But get the service manual, it steps you through the entire process.
Chris
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Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
You do have the temperature switch in the passenger side head connected with a green TCS jumper harness correct? And that jumper harness is connected to the blue wire that exits the engine harness between the firewall and passenger side head?
cc
cc
