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Chapter 9 General Engine Troubles and Their
Troubleshooting
Section 1 Overview
The wide application of the electronic technologies to the vehicles brings innovation on diagnosis of the
vehicle, many varieties of diagnosis instruments that are very effective and efficient for the vehicle diagnosis
are innovated. Once the fault occurs, the best choice is to go to service station for help. However, even the
most advanced instrument has its limit. For some faults, manual diagnosis is far more convenient and easier
than that of instrument. In case of the crack, distortion and leakage of the components, the manual diagnosis
is even superior to the instrument diagnosis. The faults occurred shall be carefully analyzed and troubleshot
in accordance with the repair manual for normal usage.
Section 2 General Engine Fault and Troubleshooting
I. Fuel pipeline and circuit fault causing the engine starting failure
engine starting failure normally include: starter does not run or starter runs but fails to crank the engine, or
cranks the engine but cranks slowly; starter can crank but fail to start the engine. There are many causes that
result in starting failure, such as failures in starting system, ignition system, fuel injection system and engine
mechanical failure.
1. starter does not run or fails to crank the engine or cranks slowly
(1) Symptom: starter does not run or spongy rotation
(2) Causes:
b. Low battery voltage, excessive battery discharge, damaged generator or failure in charging circuit;
c. Battery terminal rust and backed out;
d. Failure in starting circuit, ECU can not receive STA signal;
e. Damaged starter.
2. engine can not start and crank
(1) Symptom
With the start switch on, starter can crank but fail to start the engine.
(2) Causes
a. Empty fuel tank;
b. Electrical fuel pump inoperative;
c. Injector inoperative;
d. Low fuel pressure;
e. Unreasonable starting operation;
f. Damaged throttle position sensor or no signal is sent to ECU due to the open in throttle position
sensor circuit;
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