Fault symptom
Flameout, poor idle speedChapter 9 Engine EFI SystemI. Outline This system includes sensor that detects engine functioning. Engine ECU utilizes sensors installed at differ-
ent parts of engine to measure various working parameters of engine, accurately control oil injection quantity
according to control procedure set in engine electronic control unit, so engine could work in optimum mode
under various operating conditions, i. e. optimal power output, the most economical oil consumption, optimal
exhaust emissions. Engine ECU is capable of start up control, idle speed closed-loop control, air fuel ratio
closed-loop control, canister control, transient operation control, angle of ignition control, knocking control, air
conditioning control, coasting fuel cutoff and overspeed fuel cutoff control, ternary catalyst heating and protec-
tion control, system self-diagnosis etc.II. Inspection of control element1. Manifold intake pressure temperature sensor
(1) The part to measure intake pressure is piezo type sensor, could provide controller with "load signal "
according to the difference between atmospheric pressure and manifold pressure; controller will supply 5V
voltage, and feed back 0-5V voltage to controller according to different intake pressures. The part to measure
intake temperature is NTC type (negative temperature coefficient) sensor, resistance changes with intake
temperature, this sensor conveys a voltage representing intake temperature change to the controller.
(2) Simple measuring method:
Temperature sensor part: (remove joint) turn digital multimeter
to Ohm position, two meter pens connect sensor 1 #, 2 # pinrespectively, rated resistance is 2. 5k ohm±5% at 20°C, correspond-ing resistance value may be measured from the above characteristic
curve. Simulation method may also be used for measurement, spe-
cific procedure is to use electric drier to blast sensor (pay attention not
to be too close), observe change of sensor resistance, here resistanceEngine EFI System-Engine EFI System5-120Possible cause
There is abnormal high voltage or reverse heavy current during useVacuum
unit is damaged during repair
Repair precautions: it is prohibit to use high pressure gas to impact vacuum unit during repair; when replace
sensor case of trouble, check whether generator output voltage and current is normal or not.1 2 3 4Manifold intake pressure temperature
sensor Intake pressure sensor feature cureIntake temperature feature curve
Output voltageAbsolute pressureTemperatureResistance
