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Discussion Starter · #1 · (Edited)
Recently several members have been having with the concept of TDC or with finding TDC on their Vulcan for the purpose of replacing the Cam Shaft Position Sensor.

This first concept to understand what TDC means. TDC means with the piston is at the maximum high point of its travel in the cylinder bore and the crank shaft is centered for that brief point where the piston is that high point. The piston at that point is at the maximum distance from the crankshaft. The photo shows a good illustration in how the cylinders are at different points in their travel up and down. That being said though we are only interested in the travel of cylinder one.

Cylinder one on the Ford Taurus 3.0 Vulcan is the cylinder on the rear of the motor next to the the firewall on the passenger side. This is also shown in the photo.

The last photo show how as the crank rotates the and the piston moves up and down what 10 degrees BTDC, TDC and 10 degrees ATDC look like.
 

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Discussion Starter · #2 · (Edited)
The second concept to understand is that it is not enough to just have the piston at TDC on cylinder one. It has to be on the compression stroke as well. A four stoke motor makes two complete revolutions for each time it fires and makes power on an individual cylinder. The piston stoke we want is when the piston is coming up and the valves are closed (the compression stroke). An easy way to determine this is to remove the spark plug for cylinder one. Using a helper to turn the motor over with a socket on the crank pulley or alternator pulley if belt tension allows turn the motor in its normal direction of rotation and you will feel the air being pushed out the spark plug hole. Then continue to rotate the motor until it reaches TDC. A compression gauge could also serve this function if working alone.

One might also why is it a big deal to worry about the compression stroke. That is because the for each complete revolution of the crankshaft the camshaft only turns one half turn. You could have the marks aligned for TDC yet insert the synchronizer 180 degrees or a half turn out of sync.



**For maximum safety disconnect the negative battery cable or unplug the coil pack.**
 

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Discussion Starter · #3 · (Edited)
The balancer on the motor is marked with degree markings to show ZERO which is TDC as well as markings to show the number of degrees BTC (Before Top Dead Center). There is also a pointer on the timing cover that you used to align the markings on the balancer. The balancer may have rust on it that will need to be hit with sandpaper to make them visible. Talcum powder or chalk can also be used to help make the marks visible.
 

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Discussion Starter · #4 · (Edited)
The missing tooth could be aligned in two ways to figure out TDC f the marks on the balancer cannot be be rendered usable. In one case using the photo from the post above you could determine where the ZERO degree marks was in reference to counting teeth and align that with the pointer on the timing cover. One could also align the center of the CKP (Crank Position Sensor) with the center of tooth number 6 after the missing tooth to determine TDC. Obviously aligning a narrow mark with a narrow one is more precise then aligning two wider objects.

One might have also noticed the TDC has a spaced away from the degree marks in the photos in the previous post while BTDC is does not have that space.
 

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Discussion Starter · #5 · (Edited)
still working on this so I you see errors or adjustments please let me know.
 

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still working on this so I you see errors or adjustments please let me know.
Tom S said:
Using a helper to turn the motor over with a socket on the crank pulley or alternator pulley if belt tension allows turn the motor in its normal direction of rotation
Would suggest for safety reasons that the battery be disconnected any time that the motor is turned by hand.
 

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Discussion Starter · #7 ·
No problem or disconnect the coil plug.
 

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No problem or disconnect the coil plug.
Easier, I always forget that! Thanks, good write-up so far, hope that it helps eliminate multiple new threads on the subject.
 

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Thank you guys for all the work and research you put into this thread. It bailed me out on resetting a camshaft synchronizer after months of dealing with the stupid check engine light and iffy idle.
 

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The second concept to understand is that it is not enough to just have the piston at TDC on cylinder one. It has to be on the compression stroke as well. A four stoke motor makes two complete revolutions for each time it fires and makes power on an individual cylinder. The piston stoke we want is when the piston is coming up and the valves are closed (the compression stroke). An easy way to determine this is to remove the spark plug for cylinder one. Using a helper to turn the motor over with a socket on the crank pulley or alternator pulley if belt tension allows turn the motor in its normal direction of rotation and you will feel the air being pushed out the spark plug hole. Then continue to rotate the motor until it reaches TDC. A compression gauge could also serve this function if working alone.

One might also why is it a big deal to worry about the compression stroke. That is because the for each complete revolution of the crankshaft the camshaft only turns one half turn. You could have the marks aligned for TDC yet insert the synchronizer 180 degrees or a half turn out of sync.



For maximum safety disconnect the negative battery cable or unplug the coil pack.
Recently several members have been having with the concept of TDC or with finding TDC on their Vulcan for the purpose of replacing the Cam Shaft Position Sensor.

This first concept to understand what TDC means. TDC means with the piston is at the maximum high point of its travel in the cylinder bore and the crank shaft is centered for that brief point where the piston is that high point. The piston at that point is at the maximum distance from the crankshaft. The photo shows a good illustration in how the cylinders are at different points in their travel up and down. That being said though we are only interested in the travel of cylinder one.

Cylinder one on the Ford Taurus 3.0 Vulcan is the cylinder on the rear of the motor next to the the firewall on the passenger side. This is also shown in the photo.

The last photo show how as the crank rot ates the and the piston moves up and down what 10 degrees BTDC, TDC and 10 degrees ATDC look like.
Some places are saying 10°ATDC, is that where you should be or rather at TDC?(replacing CMS on 99 ranger 3.0 vulcan)
 
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