Volvo Workshop Manuals
940 L4-2.3L SOHC VIN 88 B230F (1992)
Engine, Cooling and Exhaust > Engine > Timing Components > Timing Belt > Component Information > Fundamentals and Basics > General Information > Page 3433
Timing Belt: Fundamentals and Basics
TIMING BELT, GENERAL INFORMATION
The timing belt synchronizes (times) the opening and closing of the intake and exhaust valves with the movement/stroke of the pistons. The timing
The crankshaft represents the movement of the pistons while the camshaft controls the opening and closing of the valves. The timing belt connects
In 4 stoke engine each piston must complete 4 separate strokes (intake, compression, power, and exhaust) to complete a cycle. For a single
The camshaft controls the opening and closing of the valves. During the four piston strokes of an engine cycle the intake and exhaust valves
NOTE: The intake valves will open and close only during the intake stroke and the exhaust valves will open and close only during the
This 2 to 1 reduction is accomplished by making the circumference of the camshaft pulley twice as large as the crankshaft pulley. This allows
NOTE: The distributor also requires only one rotation for every two rotations of the crankshaft.
FIRST INDICATIONS OF A BROKEN BELT
1. The engine will immediately die or fail to start.
it will sound more like "RirRirRirRir" with no detectable rhythm.
When the timing belt brakes the camshaft and distributor quit rotating.
Without distributor rotation the ignition system stops producing spark and the engine immediately dies or fails to start.
Without the rotation of the camshaft the intake and exhaust valves stop opening and closing. This prevents the pistons from developing
NOTE: The normal rhythmic cranking sound is a result of the starter having to work harder as each piston begins its compression stroke.
VERIFYING TIMING BELT IS BROKEN
Check for camshaft rotation while cranking the engine (with the starter or by hand, using the crankshaft bolt).
WARNING: When rotating the crankshaft by hand always disconnect the battery.
Camshaft rotation can be verified by:
Remove oil filler cap and check if camshaft is visible.
Remove valve cover and directly observe camshaft.
Remove distributor cap and check for rotor rotation (the rotor is driven by the camshaft)
Remove upper timing belt cover and check camshaft pulley rotation and belt integrity.
Other Indications the Timing Belt may be broken.
No ignition spark.
Very low compression (<15 psi) on all cylinders. Due to the low compression the following additional symptoms may be present.
While attempting to start the car, the battery strength remains high for an unusually long length of time.
The sound of the engine while attempting to restart will be different than normal. Instead of the usual rhythmic "Rir.. .Rir. . .Rir..."
NOTE: For an experienced technician this unique sound will often be the initial symptom that leads to a more in-depth check of the
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