Bad plugs, faulty ignition system
First you need to determine the inoperative cylinder. To do this, start up the engine, put it on the lowest possible speed. Then alternately remove high-voltage wire from each spark plug. If when removing the engine there is no noticeable hearing change, so we can consider this cylinder is inoperative. Remove the candle from it and inspect it: cracks, reflow, chipping is not allowed. It is best to put new set of spark plugs in all cylinders. If such a replacement is not successfull, you have to go to the next step check the ignition system.
One of the reasons for the fault could be a broken wire. If it doesn't work, the voltage doesn't reach the candles. To verify correct wire, disconnect it from the spark when the engine is started up (use rubber gloves – high voltage!) and move to a distance of 4-6 mm. the Presence of a spark is talking about a working ignition system. If there is no spark, try replacing the wire on is OK. When the spark does not appear, in this case, check the ignition module or distributor cap (if a car with a carburetor).
Low compression, lack of fuel
In other words is insufficient pressure in the cylinder. To understand whether this is so, you will need a helper and a compression gauge. For the measurement, disconnect the high voltage wire from the ignition coil, and remove the candle. In the vacant hole, insert the instrument and have an assistant key the ignition to crank the starter for a few seconds. Observe the maximum reading of the instrument. This guide operation with all the cylinders. Considered normal pressure of 10-14 bar. Minimum 8-10.
Another reason not functioning cylinder – lack of fuel-air mixture. This can occur due to improperly adjusted valve clearance, or faulty injectors. In the latter case, it is advisable to contact the technical service because of the repair work, adjustment of the injectors require special equipment.