i. Air filter is clogged;
j. Fuel leaks from injector;
k. Compression pressure of the cylinder is a low;
l. Intake temperature sensor is damaged.
(3) Analysis, diagnosis and elimination of fault
a. For electric injection engine, ignition timing in cold start mode is normally fixed, but when ignition timing is changed for
certain cause, cold start will be difficult, now make corrections;
b. Installation sequence of high voltage coil is disordered, correct it;
c. Check high voltage spark, check whether high voltage spark on the high voltage bus of distributor is normal or not and
whether high voltage spark on high voltage branch of each cylinder is normal or not. If spark on the bus is weak, replace
high voltage coil; if spark on the bus is normal, while spark on the branch is too weak, it indicates that there is current
leakage on the distributor cap and distributor rotor, therefore, replace it. In addition, too large spark plug gap will also
influence start performance, adjust spark plug gap to normal value.
᷉
0.8±0.1mm
᷊
d. If fuel pressure is too low, check whether voltage of storage battery is normal, otherwise eliminate or replace; check
whether there is leakage on the check valve of fuel pump, whether there is clog on the fuel filter and fuel pipe, if there is,
eliminate or replace it;
e. If there is leakage on fuel pressure adjuster, gasoline tends to flee from intake manifold, making it difficult to start,
eliminate or replace it;
f. Idle control valve cannot be opened to the max. position due to mechanical abrasion, aging or fault of control circuit, now
replace the idle control valve, repair control circuit and eliminate the fault;
g. If data of water temperature sensor is not accurate, it might lead to too small fuel injection, check the water temperature
sensor according to standard data, and adjust the data;
h. Time lag of vacuum pressure sensor is large, response is not sensitive at low revolution, which leads to inaccurate fuel
injection, make adjustment or replacement;
i. If filter element of air filter is too dirty, flow resistance of air becomes too large, start is difficult, then replace the filter
element.
In a word, there are many factors that may cause the engine unable to start, make analysis according to severity of the
fault. Generally speaking, firstly check ignition system, then check air intake system, fuel system and control system, and
finally check pressure of cylinder. Check fault code before checking the fault. Diagnosis and elimination process for engine
start failure is shown in Fig. 355.
II. Oil and Circuit Faults that Cause the Engine Hard to Start
Engine start difficulty refers to the fact that starter could drive the engine to rotate at normal speed, and there are evident
ignition signs, but the engine cannot start, or successive starting attempts or long time rotation of starter is required for
starting the engine. For difficult start, identify whether it appears in cold auto, warm auto or appears on both occasions.
(1) Symptom of fault:
During start, rotating speed of crankshaft is normal, but it needs a longer time to start, or fails to start even with evident
ignition signs
(2) Cause of fault:
a. Air filter is clogged;
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Содержание JL481Q
Страница 1: ......
Страница 9: ...5 Fig 3 Components Assembly Drawing of MR479Q MR479QA Engine ...
Страница 10: ...6 Fig 4 MR479Q MR479QA Engine and Its Power System ...
Страница 11: ...7 Fig 5 Assembly Drawing of Engine and Its Auxiliaries MR479Q MR479QA ...
Страница 12: ...8 Fig 6 Electronic Control Fuel Injection System in Engine MR479Q MR479QA ...
Страница 13: ...9 Fig 7 Front view of Engine JL481Q MR481QA ...
Страница 14: ...10 Fig 8 Sectional elevation of Engine JL481Q MR481QA ...
Страница 15: ...11 Fig 9 Electronic Control Fuel Injection System in Engine JL481Q MR481QA ...
Страница 21: ...17 Fig 13 Exterior Feature of JL481Q Engine Power Me N m Torque Pe Kw ge g kwh Fuel Consumption Ratio ...