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Can you help me with the next fault analysis and maintenance of Mazda cold car?
There are many reasons why cold start is difficult. Here are some common factors that make cold start difficult.

(1) Oil circuit and instrument section

1, insufficient gasoline pressure

Cause: (1) There is a leak in the one-way valve in the oil circuit, which can't keep enough starting pressure of the oil supply system.

(2) There is a leak in the injector, and the system pressure cannot be maintained.

Check and solution: connect the fuel pressure gauge externally and restart. After the pressure reaches the standard, turn off the fire for 4-6 hours, and then check the pressure gauge. If it can't keep the normal value, it means that the check valve and the oil nozzle are leaking.

2. The failure of gasoline pump makes it difficult to start.

Cause: the fuel pump is excessively worn, and the gasoline pump can't reach the starting pressure even if it works, which makes it difficult to start.

Inspection and solution: connect the fuel pressure gauge externally, open the key door and make the gasoline pump work. Although the pressure has increased, it still can't reach the specified pressure. Replace the gasoline pump.

3. The filter screen of gasoline filter and gasoline pump is too dirty to start.

Cause: The fuel can't reach the starting pressure due to the addition of dirty gasoline or the blockage of the filter screen or gasoline filter in front of the gasoline pump by gasoline impurities deposited in the fuel tank for a long time.

Inspection and solution: (1) Replace the gasoline filter;

(2) Take the gasoline pump out of the fuel tank, check the filter and clean it.

4. Gasoline contains too much water.

Reason: The added gasoline contains water. Because there is too much water in the air, the fuel tank is not closed tightly. The wet air in the fuel tank is affected by the temperature difference between day and night, which condenses into water droplets and sinks into the fuel tank.

Inspection and solution: replace the gasoline filter and clean the fuel tank.

5. Add ethanol gasoline.

Reason: Because ethanol gasoline contains a certain amount of water, the factors of water exceeding the standard are the same as above. Ethanol gasoline has a certain cleaning function, which washes off oil stains and some impurities on the inner wall of oil tank and pipeline, resulting in blockage of oil pump filter screen or nozzle.

Inspection and solution: clean the oil circuit and oil tank and replace unleaded gasoline.

6. Reasons for carbon deposition on fuel nozzle: Long-term carbon deposition leads to fuel nozzle blockage and fuel nozzle can't work normally.

Inspection and solution: clean the fuel injector.

7. Carbon deposit at air inlet

Cause: Due to long-term low-speed driving, a layer of carbon deposit is formed on the wall of the air inlet pipe. During start-up, the fuel sprayed by the fuel injector is absorbed into the carbon deposit, which makes the mixture too thin and difficult to start.

8. The throttle valve is too wide.

Cause: Carbon deposition causes the throttle to be too wide and the mixture to be too thin, which affects the normal start.

Inspection and solution: check the carbon deposit on the throttle, carry out necessary cleaning and re-match the throttle.

(2) Electrical appliances and startup procedures

1, temperature and pressure sensor failure

Cause: The normal signal cannot be provided, resulting in the failure of the trip computer to correctly provide the fuel injection required for starting. Generally speaking, a cold start requires a rich mixture.

Inspection and solution: Check or replace the pressure and temperature sensors.

2. Temperature controller failure

Cause: The normal signal can't be provided normally, and the trip computer can't work normally.

Inspection and solution: use 5052 or 5 1 1B detector to check the fault code and replace it.

3, air flow meter failure

Cause: The normal signal can't be provided normally, and the trip computer can't work normally.

Inspection and solution: use 5052 or 5 1 1B detector to check the fault code and replace it.

4. Ignition coil failure

Cause: Normal high-voltage electricity cannot be provided to ignite the spark plug. Resulting in uneven ignition and difficult starting.

Check and solution: Check whether the ignition coil of a cylinder works after starting, and replace the ignition coil.

5. Spark plug failure

Cause: The spark plugs of individual cylinders do not work, which leads to uneven ignition and difficult starting. The gap between spark plugs is too large, which leads to high ignition voltage, high resistance and difficult ignition.

Inspection and solution: check the working condition of each cylinder after starting, and replace the spark plug for inspection if there is any cylinder missing.

6, oxygen sensor failure

Cause: It is difficult to provide the correct signal to the driving computer and start it.

Inspection and solution: use 5052 or 5 1 1B detector to check the fault code. Make a replacement.

7. Three-way catalytic converter is blocked

Cause: The use of leaded gasoline and dirty gasoline blocked the three-way catalytic converter, and the engine emission resistance increased, making it difficult to start.

Inspection and solution: clean or replace the three-way catalytic converter if necessary.

8.OBD restrictions

Reason: Because OBD controls the emission of exhaust pollutants, when the exhaust value exceeds the emission requirements at the moment of start-up, the computer will automatically cut off the operation of the over-standard emission cylinder to control the exhaust emission. This will lead to insufficient starting of the cylinder, making it difficult to start naturally. There will be jitter after starting because the first cylinder of the engine does not work.

Inspection and solution: It is recommended to use spark plugs with low heat exchange value.