Timing Completely off. I've taken the timing belt off the crankshaft, not completely off, just off the crankshaft. The piston is at tdc, how do I set the crankshaft at tdc.

Setting the cam timing in the SC400 incorrectly can result in valve damage and possible piston damage. If you already have it apart it may be too late. The engine has to be at TDC for the crankshaft before removal of the timing belts. Rolling the cams independent of crankshaft will cause an open valve to contact the piston.(very expensive)

It must be broke, if the crankshaft is turning all the other belts, but not the timing belt. Pull off the timing belt cover to investigate. If the belt is good, maybe the woodruff key for the crankshaft sprocket has fell out. You would see the crankshaft turning, but not the crankshaft sprocket that turns the timing belt-if that were the case.

TDC is an acronym for Top Dead Center. It is when the piston has reached the very top of its travel and there is nowhere for the piston to go but down. If you align the timing marks on the engine, the piston will be at TDC with the valves on #1 closed.

To position your crankshaft and cam to the correct position, it should be done BEFORE removing the belt if possible. If the belt has already been removed and/or the belt was broken, the same principles apply, but you will have to go about it completely different.

Turn the engine clockwise to align the "O" on the crankshaft pulley with the "O" on the outer timing belt cover.
Remove the plug in the outer timing belt cover and look through the hole. The timing marks on the camshaft pulley should align with the cover pointer. If they do not align, rotate the crankshaft one full revolution and align the "Os" again. They should now align. When every thing is lined up like this, your engine is timed to #1 at TDC and the valves on #1 cylinder will be closed.

Now if the belt has already been removed or if the belt was broken, You may have to temporarily put the outer cover back on. You may have to put it on and take it off several times until you get things lined up. Time the crankshaft "Os" first. It will not matter which rotation you are on if the belt is not installed. (TDC is TDC - the piston doesn't really care where the valves are - that's the camshaft's problem LOL)
After the crank shaft is lined up, turn the camshaft so the timing marks line up with the pointer. Then remove the front cover and install your belt.

After setting the timing belt tensioner, rotate the engine two full turns clockwise and recheck to make sure that all the timing marks still line up. If they do not - repeat the procedure.

TIMING BELT & SPROCKETS R & I
NOTE: Some procedures may differ slightly due to engine
construction.
Removal
1) Remove all necessary air ducts. Position No. 4 piston at
TDC of compression stroke. Align timing marks. See Fig. 2. Remove fan
and fan shroud. Remove belts. If necessary, remove radiator and
splashguard.
2) Prevent engine from rotating and remove crankshaft timing
pulley retaining bolt. Remove upper and lower timing belt covers.
Remove spring from tension pulley. Loosen adjusting bolt and move
pulley toward water pump. Remove timing belt.
CAUTION: Ensure pistons are at TDC when rotating camshaft or damage
may result.
Inspection
1) Handle timing belt carefully. Avoid twisting or kinking
belt. Do not allow belt to become contaminated by water, oil, dirt or
other contaminates. Inspect belt for cracks or damage. If necessary,
replace.
2) Measure tension pulley spring length and force. Spring
length should not exceed 2.76" (70.2 mm) and spring force should not
be less than 197-347 lbs. (27-48 kg).
3) Replace tension pulley spring if not within specification.
Installation
1) Pull tensioner fully toward water pump side and
temporarily tighten retaining bolt. Ensure No. 4 cylinder is at TDC on
compression stroke by rotating crankshaft until keyway aligns with
mark on front crankshaft seal housing (12 o'clock). Rotate camshaft
until timing mark on cam gear (arrow) aligns with mark on upper
camshaft cover (notch). See Fig. 2.
NOTE: When timing marks are aligned as stated above, No. 4 piston
is at TDC on compression stroke.
2) Position timing belt over crankshaft sprocket, oil pump
sprocket, camshaft sprocket and tensioner in that order. Ensure belt
is positioned in sequence given and without slack between sprockets.
Loosen tension sprocket adjusting bolt allowing spring tension to
tighten belt. Tighten adjusting bolt temporarily.
3) Temporarily install crankshaft pulley bolt and rotate
crankshaft 2 complete revolutions in opposite direction of engine
rotation, until marks on crankshaft and front oil seal retainer are
aligned again. See Fig. 2. Loosen tensioner lock bolt, allowing
tesioner spring to fully adjust tension. Tighten tensioner lock bolt.
4) Install timing belt covers. To complete installation,
reverse removal procedures. Tighten all bolts to specification. See
TORQUE SPECIFICATIONS table at end of this article.
Fig. 2: 2.3L & 2.6L Timing Alignment Marks
Courtesy of Isuzu Motor Co

I found a 2.0L VW engine for a Cabrio. Not sure if this is the right one, but here goes:

REMOVAL & INSTALLATION

NOTE: Do not turn the engine or camshaft with the timing belt
removed. The pistons will contact the valves and cause internal engine damage.

Gasoline Engines






Fig. 1: Adjusting the belt tension on a 2.0L 8 valve








Fig. 2: Remove the timing belt cover








Fig. 3: Align the timing marks








Fig. 4: Locate the tensioner








Fig. 5: Loosen the tensioner bolt








Fig. 6: Mark the belts direction of rotation

1. Disconnect the negative battery cable and remove the accessory drive belts,
   crankshaft pulley and the timing belt cover(s).
   
2. Temporarily reinstall the crankshaft pulley bolt and turn the crankshaft to
   TDC of No. 1 piston. The mark on the camshaft sprocket should be aligned with
   the mark on the inner timing belt cover or the edge of the cylinder head.
   
3. With the distributor cap removed, the rotor should be pointing toward the
   No. 1 mark on the rim of the distributor housing. On 8 valve engines, the notch
   on the crankshaft pulley should align with the dot on the intermediate shaft
   sprocket.
   
4. Loosen the locknut on the tensioner pulley and turn the tensioner
   counterclockwise to relieve the tension on the timing belt.
   
5. Slide the timing belt from the sprockets.
   To install:
   
   
6. Check the alignment of the timing marks. On 16 valve engines, the mark on
   the tooth should align with the mark on the rear belt cover.
   
7. Install the new timing belt and tension the belt so it can be twisted 90°at
   the middle of it's longest section, between the camshaft and intermediate
   sprockets.
   
8. Recheck the alignment of the timing marks and, if correct, turn the engine 2
   full revolutions to return to TDC of No. 1 piston. Recheck belt tension and
   timing marks. Readjust as required. Torque the tensioner nut to 33 ft. lbs. (45
   Nm).
   
9. Install the belt cover and accessory drive belts.
   
10. If the belt is too tight, there will be a growling noise that rises and
    falls with engine speed.

Diesel Engines

Some special tools are required. A flat bar, VW tool no. 2065A, is used to
secure the camshaft in position. A pin, VW tool no. 2064, is used to fix the
pump position while the timing belt is removed. The camshaft and pump work
against spring pressure and will move out of position when the timing belt is
removed. It is not difficult to find substitutes but do not remove the timing
belt without these tools.
NOTE: Do not turn the engine or camshaft with the timing belt
removed. The pistons will contact the valves and cause internal engine damage.

1. Disconnect the negative battery cable and remove the accessory drive belts,
   crankshaft pulley and the timing belt cover(s). Remove the camshaft cover and
   rubber plug at the back end of the camshaft.
   
2. Temporarily reinstall the crankshaft pulley bolt and turn the crankshaft to
   TDC of No. 1 piston. The mark on the camshaft sprocket should be aligned with
   the mark on the inner timing belt cover or the edge of the cylinder head.
   
3. With the engine at TDC, insert the bar into the slot at the back of the
   camshaft. The bar rests on the cylinder head to will hold the camshaft in
   position.
   
4. Insert the pin into the injection pump drive sprocket to hold the pump in
   position.
   
5. Loosen the locknut on the tensioner pulley and turn the tensioner
   counterclockwise to relieve the tension on the timing belt. Slide the timing
   belt from the sprockets.
   To install:
   
   
6. Install the new timing belt and adjust the tension so the belt can be
   twisted 45 degrees at a point between the camshaft and pump sprockets. Torque
   the tensioner nut to 33 ft. (45 Nm).
   
7. Remove the holding tools.
   
8. Turn the engine 2 full revolutions to return to TDC of No. 1 piston. Recheck
   belt tension and timing mark alignment, readjust as required.
   
9. Install the belt cover and accessory drive belts.
   
10. If the belt is too tight, there will be a growling noise that rises and
    falls with engine speed.

I'm going to copy the procedure from Autozone.com below. I've never seen such a complicated way of getting the tension right, but better to follow their instructions, I guess. Note that they ask you to loosen the rocker shafts, but they never tell you to put them back. I will add that.


To install:

6. Remove both cylinder head covers and loosen all rocker arm shaft retaining bolts.

The rocker arm shaft bolts MUST be loosened so that the correct belt tension can be obtained.

1. Install the tensioner and the return spring. Using a hexagon wrench, turn the tensioner clockwise, then temporarily tighten the locknut.
2. Make sure that the timing belt is clean and free from oil or water, before installation.
3. Install the timing belt. Align the white lines on the belt with the punchmarks on the camshaft and crankshaft sprockets. Be sure to have the arrow on the timing belt pointing toward the front belt covers.

A good way (although rather tedious) to check for proper timing belt installation is to count the number of belt teeth between the timing marks. There are 133 teeth on the belt; there should be 40 teeth between the timing marks on the left and right-side camshaft sprockets, and 43 teeth between the timing marks on the left-side camshaft sprocket and the crankshaft sprocket.

1. While keeping the tensioner steady, loosen the locknut with a hexagon wrench.
2. Turn the tension approximately 70-80 degrees clockwise with the wrench, then tighten the locknut.
3. Turn the crankshaft in a clockwise direction several times, then slowly set the No. 1 piston to TDC of the compression stroke.
4. Apply 22 lbs. (10 kg) of pressure (push it in) to the center span of the timing belt between the right-side camshaft sprocket and the tensioner pulley, then loosen the tensioner locknut.
5. Using a 0.0138 in. (0.35mm) feeler gauge (the actual width of the blade must be 1/2 in. or 12.7mm thick), positioned as shown in the illustration, slowly turn the crankshaft clockwise. The timing belt should move approximately 2 1/2 teeth. Tighten the tensioner locknut, then turn the crankshaft slightly and remove the feeler gauge.
6. Slowly rotate the crankshaft clockwise several more times , then set the No. 1 piston to TDC of the compression stroke; recheck all alignment marks.
7. Install the upper and lower timing belt covers.
8. Connect the negative battery cable.

When installing the rocker arm shafts, be certain that they are installed in their original positions.

1. Make sure the camshaft knock pin is at the top of the camshaft and that the lobe is not in the lifted position. If servicing the left-side cylinder head, set the No. 1 piston at TDC of its compression stroke, then tighten the rocker shaft bolts for cylinder No. 2, 4 and 6 cylinders. If servicing the right-side cylinder head, set the No. 4 piston at TDC of its compression stroke and tighten the rocker shaft bolts for cylinder No. 1, 3 and 5 cylinder rocker shaft bolts. Tighten all bolts gradually, in two or three stages, to 13-16 ft. lbs. (18-22 Nm).
2. Install the cylinder head cover(s).

TDC is top dead center/ remove spark plug on cylinder no. 1/ rotate the crankshaft pulley using a socket wrench and power handle and check if the piston on your cylinder no. 1 reach the top center that is TDC/ remove timing belt cover and locate a synchronized marking on your camshaft and crankshaft pulley/ remove old timing belt/ install a new one but make sure that the mark on your camshaft and crankshaft is perfectly synchronized before putting the cover/ manually rotate the crankshaft pulley again and see if it rotates 360 deg. freely then you can be sure you did the job correctly.

take the timing belt off reset the crank at 0 with # 1 piston at TDC ensure that both cams are up at twelve 'oclock with belt on, when the tension is released and the tensioner is tightened turn the crank atleast 360 degrees and ensure that the timing does not shift before starting engine

The Isuzu is a strange animal-when you do the timing belt you set it with #1 TDC "BUT" the distributor is timed with TDC #4 I found this the hard way and finally had to buy a cd with the procedures on it. Send me an e-mail address and I will forward the associated pictures &
info to you.
Jim Young
[email protected]

TIMING BELT & SPROCKETS R & I
NOTE: Some procedures may differ slightly due to engine
construction.
Removal
1) Remove all necessary air ducts. Position No. 4 piston at
TDC of compression stroke. Align timing marks. See Fig. 2. Remove fan
and fan shroud. Remove belts. If necessary, remove radiator and
splashguard.
2) Prevent engine from rotating and remove crankshaft timing
pulley retaining bolt. Remove upper and lower timing belt covers.
Remove spring from tension pulley. Loosen adjusting bolt and move
pulley toward water pump. Remove timing belt.
CAUTION: Ensure pistons are at TDC when rotating camshaft or damage
may result.
Inspection
1) Handle timing belt carefully. Avoid twisting or kinking
belt. Do not allow belt to become contaminated by water, oil, dirt or
other contaminates. Inspect belt for cracks or damage. If necessary,
replace.
2) Measure tension pulley spring length and force. Spring
length should not exceed 2.76" (70.2 mm) and spring force should not
be less than 197-347 lbs. (27-48 kg).
3) Replace tension pulley spring if not within specification.
Installation
1) Pull tensioner fully toward water pump side and
temporarily tighten retaining bolt. Ensure No. 4 cylinder is at TDC on
compression stroke by rotating crankshaft until keyway aligns with
mark on front crankshaft seal housing (12 o’clock). Rotate camshaft
until timing mark on cam gear (arrow) aligns with mark on upper
camshaft cover (notch). See Fig. 2.
NOTE: When timing marks are aligned as stated above, No. 4 piston
is at TDC on compression stroke.
2) Position timing belt over crankshaft sprocket, oil pump
sprocket, camshaft sprocket and tensioner in that order. Ensure belt
is positioned in sequence given and without slack between sprockets.
Loosen tension sprocket adjusting bolt allowing spring tension to
tighten belt. Tighten adjusting bolt temporarily.
3) Temporarily install crankshaft pulley bolt and rotate
crankshaft 2 complete revolutions in opposite direction of engine
rotation, until marks on crankshaft and front oil seal retainer are
aligned again. See Fig. 2. Loosen tensioner lock bolt, allowing
tesioner spring to fully adjust tension. Tighten tensioner lock bolt.
4) Install timing belt covers. To complete installation,
reverse removal procedures. Tighten all bolts to specification. See
TORQUE SPECIFICATIONS table at end of this article.
Fig. 2: 2.3L & 2.6L Timing Alignment Marks
Courtesy of Isuzu Motor Co.

This will take about 3-4 hours. If you look at the drive belts, they will all have to be taken off to get to the timing belt. The engine crankshaft has to be positioned for marks to line-up. The crankshaft will have to be prevented from turning so you can take off its drive pulley. Rotate until the alignment cylinder is near TDC, remove sparkplug, then packing a small rope on top of the piston prevents the engine from turning.. Once you change one timing belt, you will never buy another car with a timing belt again. You can get a manual on eBay.