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G-Scan Compression Test

The document describes three diagnostic tests to identify issues with engine cylinders and fuel injectors using a G-scan tool: 1) A compression test measures cylinder rpm to identify low compression from leaks or defects. 2) An idle speed test compares cylinder rpm without fuel adjustments to find injectors supplying excessive or insufficient fuel. 3) An injection quantity test observes fuel adjustment values during a power balance test to identify injectors supplying less or more fuel than others, with large adjustments indicating defective injectors.

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476 views1 page

G-Scan Compression Test

The document describes three diagnostic tests to identify issues with engine cylinders and fuel injectors using a G-scan tool: 1) A compression test measures cylinder rpm to identify low compression from leaks or defects. 2) An idle speed test compares cylinder rpm without fuel adjustments to find injectors supplying excessive or insufficient fuel. 3) An injection quantity test observes fuel adjustment values during a power balance test to identify injectors supplying less or more fuel than others, with large adjustments indicating defective injectors.

Uploaded by

ອູ່ ໄຊ ອິນເຕີ
Copyright
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↘ Compression test ↘ Idle speed comparison test ↘ Injection quantity comparison test

NOTE: test these items with G-scan


1. With compression test, G-scan measures the rpm of each cylinder while you crank the
engine with the injectors not operating, by comparing the rpm of each cylinder, you can
check the mechanical defect of the cylinder, if the rpm of one cylinder is too HIGH, it means
the compression of that cylinder is too LOW due to leak or other mechanical defected.
2. Idle speed comparison test is a function that allows you to measure the rpm of each
cylinder when the fuel adaptation is not applied, because the adaptation is not applied, all
fuel injectors operate under the same condition without correction or adjustment. Therefore,
you can check the defect of the injector by comparing the rpm per cylinder: HIGHER rpm
means excessive fuel injection; LOWER rpm means insufficient fuel injection.
3. Injection quantity comparison test can help you identify the status of each injector by
observing the change of injection volume correction of each cylinder while the G-scan is
performing the power balance test. The engine ECU is trying to adjust the fuel injection
volume to maintain the stable idling during the power balance test is running. If the test
result value is increase more than the other cylinder, it means that the injection volume is
smaller and vice versa, if the change of the correction volume is too big, then we can say the
injector of that cylinder is defected. If one injector is defected, then the correction value will
be much bigger than 4.

7.3 Injection quantity comparison


*The positive correction value:
->The fuel injection of the cylinder is
less than that of other cylinder.
*The negative correction value:
->The fuel injection of the cylinder is
more than that of other cylinder.
*Extreme correction value identifies a
problematic injector.
After replacing an injector with new one,
reset & confirm the engine condition.

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