Engine diagnostic techniques (Chevrolet Captiva 1)

Engine diagnostics

Reviewing the provided description and system operation information will help determine whether the condition described by the customer causes the engine to operate abnormally or normally.

Strategy-based diagnostics

View system operations To become familiar with the system functions, See Section 1A1, General Engine Data - 2.0 Diesel and Section 1F1, Engine Controls - 2.0 Diesel - General Information.
Perform a diagnostic check of the engine management system, See Section 1F1, Engine Controls - 2.0 Diesel - Diagnostics.

All diagnostics on a vehicle should follow a logical process. Strategy-based diagnostics is a unified approach to performing repairs on all vehicle systems. The process flow chart in strategy-based diagnostics can always be used to solve system problems. The diagnostic process flow chart is the starting point when repairs are required. For a detailed explanation of strategy-based diagnostics and the process flow chart, See Section 1F1, Engine Controls - 2.0 Diesel - Diagnostics.

Visual/physical inspection

Inspect the vehicle for any additional equipment installed on the vehicle after sale that may adversely affect engine performance.
Inspect easily accessible or highly visible system components for clear evidence of damage or conditions that may cause the symptom.
Check the engine lubrication system as follows:

is the oil level correct?,
is the lubricant viscosity correct?,
is the oil filter being used correctly?
whether the oil is contaminated and whether there are any carbon particles in it.

Confirm the accuracy of the operating conditions under which the engine malfunction occurs. Pay attention to factors such as:

engine speed (rpm),
ambient temperature,
engine temperature,
engine warm-up time and
the speed of a car on the road.

Compare engine operating noises, if applicable, with those of a known good engine to ensure that no attempt is being made to diagnose normal operating conditions.

Intermittent

If faults occur periodically, test the vehicle under the same conditions as reported by the customer to verify that the system is operating correctly.

Compression check

Caution! To prevent the engine from starting, disconnect the crankshaft position (CKP) sensor connector. However, do not remove the fuel pump fuse from the fuse box or disconnect the high-pressure pump connector to prevent the engine from starting. Since the high-pressure pump is lubricated by the fuel through the fuel pump, if you remove the fuel pump fuse or disconnect the high-pressure pump connector, the high-pressure pump will be damaged. Check the compression pressure for each cylinder. Low compression pressure may cause valve and cylinder malfunction. When checking the cylinder compression, pay attention to the following conditions:

The engine must be at normal operating temperature.
The battery must be fully or nearly fully charged.
The duration of engine cranking for compression testing should be less than 10 seconds with intervals of 30 seconds.

Disconnect the crankshaft angle (CKP) sensor connector.
Remove the fuel pump relay from the engine compartment fuse box.
Remove injector #1 from the cylinder head.
Turn the engine crankshaft with the starter for 5 seconds to remove any foreign matter present in the cylinder.
Install the compression pressure gauge (EN-48248) into the nozzle hole of the cylinder being tested.

Note: The compression pressure gauge and injector have a similar configuration. Therefore, the procedure for installing the compression pressure gauge is similar to installing the injector. Refer to Section 2F1, Engine Controls. Section 1F2, Engine Controls.

Using the vehicle's starter, rotate or crank the engine for no more than 10 seconds at 30-second intervals.

Caution! During the compression pressure test, fuel may leak from the fuel lines on the injector side of the cylinder being tested. To prevent fuel from dripping from the fuel lines onto the engine casing, place a container underneath.

Normally, the compression pressure gauge reading for each cylinder should be 2600 kPa (377 psi). The maximum pressure difference between each cylinder is approximately 10%.
Look at the meter data obtained from four "kicks" per cylinder from cranking the engine. Explanations of the readings are given in the following descriptions:

Normal condition: Rapid and uniform increase in compression pressure to a certain value in each cylinder.
Piston rings are faulty: Compression pressure is low on the first stroke and tends to increase on the following strokes, but still does not reach normal compression pressure. Compression pressure improves significantly when adding oil to the cylinder.
Valves are faulty: Low compression pressure on the first stroke. Compression pressure does not tend to increase on subsequent strokes. Compression pressure does not improve significantly when adding oil to the cylinder.