To determine the exact cause and to establish what kind of valve went bankrupt, do the following.

- Run the engine at idle.

- Run the engine for a few minutes.

- Open the hood.

- Remove the cap from the spark of the first cylinder. If the engine speed is changed (slowed), this cylinder works.

- Put the cap back on and remove the cap from the spark to the second cylinder. Repeat the previous step for all cylinders.

- Check the operation of all cylinders, define broken. If the engine rpm when removing spark from cap has not changed - this cylinder is not working. This may be several reasons.
The first reason – the outside of the candle. Remove the spark plug and replace it with a new one (better to replace the whole set). Start the engine. If the engine works the same as before – a candle at anything. If the engine is stopped troit – the issue is resolved and she was all into the broken candle.
The second reason – the lack of spark on the candle, i.e., the wiring or the distributor. To check for spark remove the glow plug from the outside of the cylinder, put on her cap and put it on the engine. Scroll the engine a starter. If the spark is there, the electrician and the dispenser at anything. If there is no spark, check the distributor, distributor cap, Cam, wires, high voltage wires and caps.
If the ignition system is serviceable, there's two reasons why the engine troit: it's either a burnt valve or destruction of the piston (broken rings, sticking of piston rings, the destruction of the walls of the piston). Start the engine and let it run. In this case observe the breather. Then turn the engine off, turn the candle broken cylinder and inspect it. If the spark plug is clean and dry – burned valve. At the same time from the breather to get air or light smoke.
If the spark plug is wet with oil, and the breather out thick smoke, it means that the problem is in the piston: stuck or broken rings, or damaged piston. Performing such a test, it is possible to be 99% sure the reason why but the fact, and find out which of the valves failed.