Valve Adjustment Sequence for 4-Cylinder Diesel Engines?
3 Answers
There are mainly two methods for adjusting the valves of a four-cylinder diesel engine. Here are the details: 1. Cylinder-by-Cylinder Adjustment Method: For a four-cylinder engine with a firing order of 1→3→4→2, this method requires locating the top dead center of the compression stroke for each cylinder and remembering the working sequence of the engine for different vehicle models. 2. Two-Step Adjustment Method: This approach involves adjusting all the valves on the engine in two steps. It is simple to operate and highly efficient. Even with more cylinders, only two adjustments are needed to complete the process. Below is additional information on the valve clearance adjustment method for four-cylinder diesel engines: 1. Locate the top dead center of the first cylinder's compression stroke. 2. Follow the 'Double-Row-No-In' rule: Double: Adjust both intake and exhaust valves; No: Do not adjust. 3. After adjustment, rotate the crankshaft one full turn. Then follow the 'No-In-Double-Row' rule. 4. After adjustment, recheck with a feeler gauge and readjust if necessary.
When I first started adjusting the valves on a diesel engine, I was also confused. The key is to accurately locate the top dead center (TDC) of the first cylinder. First, rotate the crankshaft to align the flywheel mark with the timing mark, then check if both the intake and exhaust rocker arms of the first cylinder can move freely—this means it's in position. For a four-cylinder engine, the general adjustment sequence is 1-3-4-2. Remember the mnemonic 'Double, In, Ex, None': first adjust both intake and exhaust valves of the first cylinder, then only the intake valve of the second cylinder, the exhaust valve of the third cylinder, and leave the fourth cylinder untouched. After that, rotate the crankshaft 360 degrees to the TDC of the fourth cylinder, and adjust the intake and exhaust valves of the fourth cylinder, the intake valve of the third cylinder, and the exhaust valve of the second cylinder in reverse order. Always remember to measure the clearance with a feeler gauge each time you adjust. For diesel engines, the intake valve clearance is approximately 0.3mm and the exhaust valve clearance is around 0.4mm, though this may vary slightly depending on the model. Finally, manually rotate the crankshaft two full turns to ensure there’s no binding, and only then is the job complete.
Over the years of working on diesel engine repairs, I've summarized that the key to adjusting valve clearance is a two-step operation. In the first step, locate the top dead center of the first cylinder's compression stroke, focusing on adjusting the valve clearances for cylinders 1 and 3: adjust both intake and exhaust valves for cylinder 1, set the intake valve clearance for cylinder 2 to approximately 0.3mm, and adjust the exhaust valve for cylinder 3 to 0.4mm. After rotating the crankshaft a full turn, the fourth cylinder reaches the top dead center of its compression stroke to begin the second step. Adjust both intake and exhaust valves for cylinder 4 to standard values, fine-tune the intake valve for cylinder 3 to 0.3mm, and set the exhaust valve clearance for cylinder 2 to 0.4mm. Always hold the adjustment screw in place when tightening the lock nut to prevent it from turning with the nut. After adjustment, it's essential to use a torque wrench; otherwise, the settings may loosen after a few thousand kilometers. Remember to perform these adjustments when the engine is cold, as adjustments made on a hot engine will result in smaller clearances.
