Camshafts are a very important part of your engine. They operate the valves along the top of your engine. These valves are used to allow the air fuel mix into the cylinder and the exhaust out. When the camshaft rotates oblong lobes force the valves open. Because of this, timing between the camshaft and crank shaft (which operates the piston) is essential. Most engines use a timing chain or belt that keeps these two shafts in sync with each other.
Diagnosing Camshaft Issues
Some engines are fitted with a decompression valve that is engaged by a special spring loaded arm mechanism on the camshaft. While the engine is running and the shaft is spinning this spring loaded arm mechanism is moved out of the way of engaging the decompression valve allowing the engine to retain compression and run normally. If this spring loaded arm mechanism fails and engages the decompression valve while the engine is running the engine will abruptly stop. If your engine turns over but immediately stops, this may be the cause.
One of the common issues we see with camshafts in our shop is caused when the camshaft drive gear gets worn down. Over time the teeth on this drive gear can become worn down until they can no longer power the shaft. Depending on the material the gear is manufactured from this can happen faster on some shafts than others. We typically see this issue with camshafts that use plastic drive gears.
Another common issue that we see in our shop happens when an engine throws a rod. When this happens the rod can impact the camshaft. The momentum from the rod being thrown can be enough to snap the camshaft.