93 Volvo 940 Threw timing belt, now won't start

if there is white smoke coming from timing belt housing then it sounds like the tensioner is locking up and causing the belt to smoke replace tensioner and belt.!!!

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you do not have a safe engine if 1994 is this the red block engine the last red block safe engine was in 1993.

Several possible reasons:-
incorrectly tensioned belt, worn dirve/driven gears, misaligned gears, oil contamination on belt, excessive heat, suspect quality belts.

Underneath the alternator facing forward is a 13 mm nut which locks the alternator in place, slacken this off and the two nuts/bolts where the alternator pivots.From the left side of the car there is a 10 mm bolt which is the tensioner, slacken this untill the alternator can be moved towards the engine sufficiently to remove the belt .Reverse this procedure to replace the belt. (depending on drives to other items you may have to remove their belts as well)

Timing belt alignment markings




Here is all the tech info for removing and replacing....hope this helps you:

4-Cylinder Engine

1. Before servicing the vehicle, refer to the Precautions section.
2. Remove or disconnect the following:
   • Negative battery cable
   • Right hand engine cover
   • Cover over the right headlamp
   • Accessory drive belt
   • Front timing cover
   • Servo reservoir
3. Position Volvo lifting beam 999 5006 or equivalent slightly in front of the front lifting eyelet for the engine. Use Volvo lifting arm 999 5383 or equivalent and Volvo lifting hook 999 5460 or equivalent to raise the front of the engine a few millimeters.
4. Remove or disconnect the following:
   • Right-hand engine mount
   • Right front wheel
5. Turn the crankshaft until the markings on the crankshaft and camshaft pulley correspond. Turn the crankshaft a further 1/4 turn clockwise and then back again until the markings correspond. The markings are illustrated. Remove the upper timing cover.
6. Slacken off the center screw for the belt tensioner slightly.
7. Turn the tensioner clockwise to 10 o'clock.
8. Remove or disconnect the following:
   • Air baffles
   • Lower belt cover
   • Timing belt

To install:

1. Turn all the pulleys listening for bearing noise. Check to see that the contact surfaces are clean and smooth. If the tensioner pulley lever or idler is seized, replace it.
2. If replacing with a new idler pulley, tighten to 18 ft. lbs. (24 Nm).
3. If replacing tension pulley, screw into place using the center bolt by hand. Ensure that the tensioner fork is centered over the cylinder block rib. Ensure that the Allen hole on the eccentric is at "10 o'clock".
4. Install the timing belt in the following order:
   1. Around the crankshaft sprocket
   2. Around the idler pulley
   3. Around the camshaft sprockets
   4. Around the water pump
   5. Onto the belt tensioner
5. Carefully turn the crankshaft clockwise until the timing belt is tensioned. The belt must be tensioned between the intake camshaft pulley, the idler pulley and the crankshaft
6. Hold the belt tensioner center screw secure. Turn the belt tensioner eccentric counter-clockwise until the tensioner indicator passes the marked position.
7. Then turn the eccentric back so that the indicator reaches the marked position in the center of the window and tighten the center bolt to 15 ft. lbs. (20 Nm).
8. Press the belt to check that the indicator on the tensioner moves easily.
9. Install or connect the following:
   • Lower belt guard
   • Air baffles
   • Upper timing cover
10. Turn the crankshaft two turns. Check that the markings on the crankshaft and camshaft pulley correspond.

NOTE Check that the indicator on the belt tensioner is within the marked area.

1. Install or connect the following:
   • Lower timing cover
   • Front timing cover and tighten to 9 ft. lbs. (12 Nm)
   • Accessory drive belt
   • Engine mount and tighten to 49 ft. lbs. (67 Nm)
   • Servo reservoir. Tighten bolts to 37 ft. lbs. (50 Nm).
   • Front wheel
   • Right hand engine cover
   • Cover over the right headlamp
   • Negative battery cable

2.4L Engine
NOTE You may need DRB scan tool to perform the crankshaft and camshaft relearn alignment procedure.

1. Remove or disconnect the following:
   
   • Negative battery cable
     
   • Right front wheel and inner splash shield
     
   • Accessory drive belts
     
   • Crankshaft damper
     
   • A/C compressor/alternator tensioner and pulley assembly
     
   • Lower front timing cover
     
   • Upper front timing cover
     
   • Right engine mount
     
   • Engine mount bracket
     
   
   NOTE This is an interference engine. Do not rotate the crankshaft or the camshafts after the timing belt has been removed. Damage to the valve components may occur. Before removing the timing belt, always align the timing marks.
   
2. Rotate the crankshaft until the Top Dead Center (TDC) mark on the oil pump housing aligns with the TDC mark on the camshaft sprocket (located on the trailing edge of the tooth).
   
3. Loosen the timing belt tensioner lock bolt.
   
4. Insert a 6mm Allen wrench into the hexagon opening located on the top plate of the belt tensioner pulley. Rotate the top plate clockwise until there is enough slack to remove the belt.
   
5. If necessary, remove the camshaft timing belt sprockets.
   
6. If necessary, remove the crankshaft timing belt sprocket using removal tool No. 6793, or equivalent.
   
7. Place the tensioner into a soft-jawed vise to compress the tensioner.
   
8. After compressing the tensioner, insert a pin (a 5/64 in. Allen wrench will also work) into the plunger side hole to retain the plunger until installation.
   

Camshaft and crankshaft alignment marks—2.4L engine




To lock the timing belt tensioner, be sure to fully insert the smaller Allen wrench into the tensioner as shown—2.4L engine





Installation of the timing belt, notice the camshaft alignment— 2.4L (VIN B) engine


To install:

1. If necessary, use tool No. 6792, or equivalent, to install the crankshaft timing belt sprocket onto the crankshaft.
   
2. If necessary, install the camshaft sprockets onto the camshafts. Install and tighten the camshaft sprocket bolts to 75 ft. lbs. (101 Nm).
   
3. Set the crankshaft sprocket to Top Dead Center (TDC) by aligning the notch on the sprocket with the arrow on the oil pump housing.
   
4. Set the camshafts timing marks so the exhaust camshaft is 1/2 notch below intake camshaft sprocket. Make sure the arrows on both camshaft sprockets are facing up
   
5. Install the timing belt starting at the crankshaft, then around the water pump sprocket, idler pulley, camshaft sprockets and around the tensioner pulley.
   
6. Move the exhaust camshaft sprocket counterclockwise to take up the belt slack.
   
7. Insert a 6mm Allen wrench into the hexagon opening located on the top plate of the belt tensioner pulley. Rotate the top plate counterclockwise until there is no slack on the belt. The tensioner setting notch will start to move clockwise. Watch the notch and continue rotating the top plate counterclockwise until the setting notch is aligned with the spring tang. Using the Allen wrench to prevent the top plate from moving, tighten the tensioner lock bolt to 220 inch lbs. (25 Nm). The setting notch and spring tang should remain aligned after the lock nut is tightened.
   
8. Rotate the crankshaft 2 revolutions and recheck the timing marks.
   
9. Check the spring tang is within the tolerance window. If not within the window, reinsert the Allen wrench and into the hexagon opening located on the top plate of the belt tensioner pulley. Rotate the top plate counterclockwise until there is no slack on the belt. The tensioner setting notch will start to move clockwise. Watch the notch and continue rotating the top plate counterclockwise until the setting notch is aligned with the spring tang. Using the Allen wrench to prevent the top plate from moving, tighten the tensioner lock bolt to 220 inch lbs. (25 Nm). The setting notch and spring tang should remain aligned after the lock nut is tightened.
   
10. Install the engine mount bracket.
    
11. Install the front timing belt covers.
    
12. Install the A/C compressor/alternator tensioner and pulley assembly.
    
13. Install the right engine mount.
    
14. Install the crankshaft damper
    
15. Install the accessory drive belts and adjust to the proper tension.
    
16. Install the right inner splash shield and wheel.
    
17. Reconnect the negative battery cable.
    
18. Perform the crankshaft and camshaft relearn alignment procedure using the DRB scan tool, or equivalent
    

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have the accessory drive belt checked and the belt tensioner.

I hope you've solved the problem by now, but there are alignment marks on the crank shaft (top pulley), idler (lower side), and cam shaft (smaller, bottom pulley) which should be aligned with stationary marks on the timing belt rear cover.

The belt has marks that align with the aforementioned marks (lines). The double marks on the belt align with the camshaft marks and the single marks with the others.

Loosen the tensioner clamp (nut) to allow the spring loaded tensioner to press on the belt and retighten the nut.

Rotate the crank shaft (clockwise, probably two revolutions) and make sure the pulley marks realign to the marks on the cover (they don't have to realign with the marks on the belt).

Rotate the crank shaft a full revolution once the belt is on and check that alignment is preserved.

Periodically loosen and retension the tensioner nut (access through a hole in the cover) to ensure that tension is maintained as the belt relaxes.

Preparation

Caution! Remove the ignition key.

Remove
the screw holding the engine stabilizer brace to the bracket on the engine
the screws holding the engine stabilizer brace to the suspension turrets
the engine stabilizer brace.

Applies only to B6xx4T engines:
Remove the plastic pipes between the turbocharger (TC) and charge air cooler (CAC) and between the air cleaner (ACL) and turbocharger (TC). Put them to one side. Remove the clamp from the intake manifold for the turbocharger (TC) for cylinders 1, 2 and 3. Turn the upper section of the pipe towards the firewall.

Relieve the load from the belt tensioner.
Remove the auxiliaries belt. See: Drive Belt\Service and Repair
Remove the upper timing belt cover.
Remove the front timing belt cover.
Lift up the servo reservoir and place it on top of the engine.Note! Ensure that the oil does not leak from the ventilation hole in the filler cap.

Seal the hose between the expansion tank and the radiator.
Disconnect the hose at the tank.
Lift up the expansion tank and place it on top of engine.

Raise the car. Remove
the right front wheel
the plastic nuts on the cover in the fender liner. Install the upper timing belt cover.
Turn the crankshaft clockwise until the markings on the crankshaft and camshaft pulleys correspond.
Turn the crankshaft a further 1/4 turn clockwise. Then turn back counter-clockwise until the markings correspond.
Remove the upper timing belt cover.

Remove the 4 vibration damper screws. Counterhold the crankshaft central nut.

Remove
the vibration damper
the auxiliaries belt
the belt cover behind the crankshaft pulley for the auxiliaries belt. Spray universal oil or similar around the rubber sleeve on the underside of the oil pump.

Remove the rubber sleeve.

Removing the timing belt

Slacken off the belt tensioner
Slacken off the center screw for the belt tensioner slightly.
Hold the center screw still.
Turn the tensioner eccentric counter-clockwise using a 6 mm Allen key.
Turn to 10 o'clock.
Unhook and remove the timing belt.Caution! Do not turn the camshafts or the crankshaft when the timing belt has been removed.


Checking the tensioner pulley and idler pulley Check bearing wear:
Spin the idler pulley and listen for noise. If replacing with a new idler pulley, tighten to 24 Nm .
Spin the tension pulley and listen for noise. When replacing, screw the tension pulley into place using the center screw.
Screw in the center screw by hand.
Ensure that the tensioner fork is centered over the cylinder block rib / bracket.
Ensure that the Allen hole on the eccentric is at "10 o'clock".

Installing the timing belt

Install the belt in the following order:
crankshaft
the idler pulley
intake cam
exhaust cam
water pump
tension pulley.Note! The variable valve timing unit on B6304S engines does not have a return spring. The unit is easily dislodged when reinstalling the timing belt.


Tensioning the timing belt

This adjustment is carried out on a cold engine. A suitable temperature is approximately 20°C / 68°F .
At higher temperatures (with the engine at operating temperature or a high outside temperature for example) the indicator is further to the right.
The illustration shows the position of the indicator when aligning the timing belt tensioner at different temperatures.
Carefully turn the crankshaft clockwise until the timing belt is tensioned. The belt must be in tension between the intake camshaft pulley, the idler pulley and the crankshaft.
Hold the belt tensioner center screw secure. Turn the belt tensioner eccentric clockwise until the tensioner indicator passes the marked position. Then turn the eccentric back so that the indicator reaches the marked position in the center of the window.
Hold the eccentric secure. Tighten the center screw to 25 Nm .
Check that the indicator is in the correct position.

Check

Press the belt to check that the indicator on the tensioner moves easily.
Install the upper timing belt cover. Turn the crankshaft 2 turns. Check that the markings on the crankshaft and camshaft pulley correspond.
Check that the indicator on the belt tensioner is within the marked area.

Finishing

Install the auxiliaries belt around the pulley on the crankshaft.
Install
the rubber sleeve on the underside of the oil pump
the vibration damper.
Use new screws.
Tighten to 35 Nm .
Angle-tighten 50°.
Use the crankshaft center nut as a counterhold
the plastic nuts for the cover in the right-hand fender liner
the right front wheel.

Lower the car.
the front timing belt cover. Tension the auxiliaries belt.
the expansion tank
the hose between the expansion tank and the radiator. Remove the lock grip pliers
the servo reservoir
the upper timing belt cover.

Applies only to B6xx4T engines:
Twist the intake pipe for the turbocharger for cylinders 1, 2 and 3 into position.
Tighten the clamp.
Install the plastic hoses between the turbocharger (TC) and the charge air cooler and between the air cleaner (ACL) and the turbocharger (TC). Tighten the hose clamps.

the engine stabilizer brace. Tighten to 50 Nm
the screw holding the engine stabilizer brace to the bracket on the engine. Tighten to 80 Nm .

Final check
Check and top up if required
coolant level
the servo fluid level. Test drive the engine.

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thanks
good luck