Fault Phenomenon
The vehicle has travelled more than 90,000 km under normal operating conditions. The repair shop carried out routine replacement and maintenance of the timing system in accordance with the vehicle service manual. However, after the timing belt was replaced, the engine failed to start unexpectedly.
Repair Process
1. The vehicle was scanned with a diagnostic scanner, and no fault codes were retrieved. The starter motor cranks normally, and the dashboard tachometer displays normal RPM during cranking. Fuel pressure, fuel injection, ignition and cylinder compression pressure were all verified to be within specification; the exhaust pipe was unobstructed. Excess fuel was purged from the cylinders, yet the engine still refused to start. A timing installation error or signal malfunction is suspected.
2.The oscilloscope was used to measure the CMP and CKP waveforms of the faulty vehicle and a normal vehicle respectively. The test result revealed that their timing positions were offset by 3 teeth.
3. Timing tool installation inspection revealed incorrect fitting of intake and exhaust camshaft pulleys. The locating pin of the intake camshaft pulley was inserted into the "EX" marking hole, while the locating pin of the exhaust camshaft pulley was fitted into the "IN" marking hole. This misalignment of camshaft timing resulted in a no-start condition.
4. After reinstalling the intake and exhaust camshafts and pulleys, a road test was carried out and the fault was eliminated.
Solutions
3.During installation, insert the locating pin of the intake camshaft into the "IN" marking hole of the pulley, and fit the locating pin of the exhaust camshaft into the "EX" marking hole of the pulley.
