Hard Starting

When Engine is Hot
This condition usually caused by an over-supply of fuel due to any of the items listed under Engine Won’t Start Due to Excessive Fuel Supply. In rare cased, an ignition coil may lose it’s efficiency when it is hot and cause ignition failure.

When Engine is Cold
Many of the conditions enumerated under Engine Won’t Start also may cause hard starting in cold weather. Of particular importance, however, are the following:

• Choke setting too lean.
• Fuel may have kerosene in it or water, or ice in bottom of tank.
• Ice in fuel filter bowl.
• Ice in fuel lines.
• Engine is cranked too slowly or won’t turn over because: (a) engine oil is too thick in sub-zero weather; (b) battery weak due to extremely low temperature.
• Another possibility, although remote, is that the water pump is jammed with ice, which will interfere with the cranking of the engine if fan belt it tight.

Due to Vapor Lock
The term vapor lock means the flow of fuel to the mixing chamber in the carburetor has been stopped (locked) by the formation of vaporized fuel pockets or bubbles caused by overheating the fuel by hot fuel pump, hot fuel lines or hot carburetor.

The more volatile the fuel the greater the tendency for it to vapor lock. Vapor lock is encouraged by high atmospheric temperature, hard driving, defective engine cooling and high altitude.

A mild case of vapor lock will cause missing and hard starting when engine is warm. Somewhat more severe vapor lock will stop the engine which cannot be started again until it has cooled off enough so that any vaporized fuel has be condensed to a liquid.

Due to Percolation
Percolation means simply that gasoline in the carburetor bowl is boiling over into the intake manifold. This condition is most apt to occur immediately after a hot engine is shut off. Most carburetors have a provision for reliving the vapor pressure of overheated fuel in the carburetor bowl by means of ports. If, however, percolation should take place the engine may be started by allowing it to cool slightly and then holding the throttle wide open while cranking the intake manifold of excess fuel.

After Long Storage

• The more volatile components in the fuel have evaporated and those remaining are not sufficiently volatile to provide a combustible mixture.
• Low or run- down battery.
• Corrosion of engine parts may result in so much friction that starter cannot crank engine at proper speed, if at all.
• Pistons, etc. may by stuck fast by gummy oil.
• Engine valves may stick open due to gummy oil deposits.
• There is the possibility that any small part essential to the running of the engine may be stuck due to gummy film or to corrosion.
• Some of these troubles are most likely to occur in hot, humid climate and near salt water.