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g. Ignition system failure;

h. Low engine compression pressure.

(3)  Diagnosis and Troubleshooting

a. First, check the fuel tank for fuel level, turn on the ignition switch, if fuel gauge pointer does not

move or fuel level warning lamp lights, then the fuel tank is empty, fuel shall be filled at this time.

b. Check that the electrical fuel pump for operation. Remove the fuel tank, you may use a wire to

connect the two jacks of the fuel pump for short, then turn on the ignition switch. The fuel pump

operation sound shall be able to be heard from the fuel tank nozzle or fuel flow can be felt with hand

pinching the tube; or remove the return hose on the fuel pressure regulator, check that the fuel

flows out; Direct judgment can be made if it is equipped with fuel pressure gage.

If  electrical fuel pump is inoperative, check whether the main fuse, main relay, fuel pump relay,

fuel pump control circuit and ECU are OK. If all of them are OK, check fuel pump circuit for open,

short or damaged check valve. Repair or replacement shall be made when problems are found.

c. If there is no injection sound in injector, check injector control circuit for fault. You may use a

testing lamp with big resistance to be connected to the injector wiring connector, turn on the ignition

switch. If the testing lamp lights up, it indicates that the injector has been damaged and shall be

replaced; if the testing lamp does not light up, check whether the main fuse, EFI relay, fuse, ignition

switch and ECU terminal are OK, repair or replace them if they are not OK.

d. If there is low fuel pressure, the injection amount would be small and the engine won't start, you

should check the fuel filter for block and fuel pump safety valve for damage and check whether the

fuel pressure regulator is within the normal range, otherwise those components shall be repaired or

replaced.

e. Electric injection engine normally spot contact start the engine.

f. Check for open in the throttle position sensor (TPS) circuit.

g. Check whether there is Diagnostic Trouble Code (DTC), if there is, check it by the DTC; if there

is not, check the high voltage spark for intensity, if it is too weak, check spark plug, high voltage

wire, high voltage coil, distributor cover for faults, if there are faults, repair or replace them.

h. Check the compression pressure in the cylinder, insert the compression pressure gauge into the

spark plug hole, completely open the throttle, measure the compression pressure while starting the

engine. If the compression pressure is less than 980kPa when engine speed is more than 250r/min,

remove and inspect the engine and troubleshoot it.

3. The engine cranks but can not start

(1) Symptom

When starting the engine,  starter can crank the engine but fail to start the engine.

(2) Causes:

a. Ignition advance angle is unfavorable;

b. Ignition is out of sequence, there is misfire;

c. High voltage spark is too weak;

d. The fuel pressure is too low;

e. fuel pressure regulator leakage;

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f. The idle control valve is faulty;

g. The water temperature sensor is damaged;

h. The vacuum pressure sensor is damaged;

i. The air filter is blocked;

j.  The injector leaks;

k. The compression pressure in the cylinder is too low;

l.  The intake temperature sensor is damaged.

(3) Diagnosis and Troubleshooting

a. Check high pressure spark, check whether the high pressure spark on the ignition coil high pressure

bus and extension are OK, if the bus spark is week, replace the ignition coil, if the bus spark is OK

while the extension spark is too week, replace the ignition coil also; In addition, excessive spark

plug clearance will influence the starting feature, the clearance of the spark plug shall be adjusted

to normal value (0.8±0.1mm);

b.  If there is low fuel pressure, check whether the battery voltage is OK, otherwise it shall be

troubleshot or replaced; check fuel pump check valve for leakage, check fuel filter and fuel pipe for

block, if there are leakage or block, replace or troubleshoot them;

c. If there is leakage for fuel pressure regulator, intake manifold is likely to be mixed with gasoline and

it is hard to start, troubleshoot or replace them;

d.  Idle control valve can not be opened to maximum position due to mechanical wear, aging or control

circuit failure, the idle control valve shall be replaced and the control circuit failure shall be troubleshot;

e. If the water temperature sensor data is not accurate, it may cause small injection, check the water

temperature sensor based on the standard data and calibrate the data;

f. There is big time lag for intake pressure temperature sensor that makes it somewhat insensitive at

low speed and result in inaccurate injection, adjustment or replacement shall be made;

g. If the air cleaner filter is too dirty, the air flow resistance is excessively big, resulting in hard start,

as a result of it, the filter shall be replaced.

In a word, there are many factors causing the starting failure of the engine, analysis shall be made based on

the severe conditions of the faults. Generally speaking, check the ignition system first, then check intake

system, fuel system, control system, at last check the cylinder pressure, check the DTC before checking the

trouble. The diagnosis and troubleshooting procedures for starting failure of the engine are shown in (Figure

148).

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Figure 148

II. Fuel pipeline and Circuit Fault for Hard Engine Starting

Hard engine starting indicates that starter can crank but fail to start the engine, or it may take multiple

consecutive starting efforts or long time rotation to successfully start the engine. For hard start fault, make

sure whether it occurs at cold or hot status or regardless of the cold or hot status.

1. Symptom

When starting, engine cranks at normal speed, but it takes longer to start or fails to start although cranks.

2. Causes:

a. Air cleaner is clogged;

b. Intake temperature sensor fault;

c. Water temperature sensor fault;

   Engine 

can 

not 

start

 
 

 

Check the starting system   

     Repair or replace the part if it is faulty

 

 

 

Check the high voltage spark

 

 

No high voltage spark or weak spark 

 

OK

 

 

Check the ignition system   

 

Is there any sign of cranking

 

 

 

 

No sign of cranking 

 

 

There is sign of cranking

 

 

Check the electric fuel pump for operation    

 

Check the air cleaner filter 

 

 

 

Operative  

 

 

       Inoperative   

 

OK 

 

Clogged

        Check the injector   

 

Check the electric fuel 

         Check the    

Replaced

 

 

 

 

           pump and its control circuit           spark clearance

Operative 

 Inoperative 

     

        Measure 

the 

fuel 

pressure

Measure the fuel pressure          Check the injector   

 

 

 

 

 

 

 

 

 

 

 

 

       Measure the vapor pressure,

 

 

 

 

 

 

 

 

 

       water temperature and intake 

Excessively low 

     OK       Check the control circuit 

 

 

           air temperature sensor

Check the fuel  

 Check thecylinder pressure 

 

 

 

       Check the cylinder pressure

pressure regulator

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d. Fuel pressure system abnormal;

e. Idle control valve fault;

f. Vacuum pressure sensor fault;

g.  Ignition system fault;

h.  The compression pressure in the cylinder is a little lower;

i. Injector leakage.

3. Diagnosis and Troubleshooting

a. Perform self-diagnosis first, check whether there is any DTC, if there is, find the reason and cause by the

DTC;

b.If it is hard for cold start but easy for hot start, check water temperature sensor and intake temperature

sensor for fault;

c. If the engine can not be started quickly in hot condition, the relief of the fuel pressure will be fast, then

repair and replacement shall be made;

d. If the spark is too weak, check high pressure coil, spark plug clearance and spark plug for carbon deposit,

repair or replace them one by one after isolating the problem;

e. Intake and exhaust valve is not completely closed, piston ring failure is likely to cause low compression

pressure in the cylinder, you should carefully repair intake & exhaust valve and seat, or replace them;

failed piston ring shall be replaced.

4. Diagnosis and Troubleshooting for hard starting and trouble shooting procedure. (Figure 149)

III. Fuel Pipeline and Circuit Faults for Poor Engine Operation

Poor engine operation includes: insufficient power, poor acceleration, poor deceleration, big fuel consumption,

rough idle and Engine overheat.

1. Insufficient Power

(1) Symptom:

Engine operation is normal without load but slow at load, insufficient power when uphill and not improved

even if the accelerator pedal is completely depressed, speed can not be increased and unable to reach the

maximum vehicle speed.

(2) Causes:

a. Air cleaner is clogged;

b. Poor intake system seal;

c. Intake pressure temperature sensor fault;

d. Low fuel pressure;

e. Broken pressure adjustor;

f. Clogged injector or poor atomization;

g. Throttle position sensor fault;

h. High pressure spark is too weak;

i. Improper valve clearance;