Q: an Iveco diesel common rail car repaired is overhauled because of excessive oil consumption. After overhauling, there is a breakdown of black smoke. The car also has the phenomenon of abnormal noise when accelerating, so it is doubted that the fuel injection advance angle is too large to cause combustion insufficiency and detonation, so the injection advance angle is adjusted, and the fuel injection amount is too large and the fuel injection amount is adjusted, and it is also invalid. Excuse me, how should the next step be overhauled? A: according to the description, there are three possibilities for me to analyze. One is to start the fault of the oil return three valve in the heating device. The return oil pressure of the valve is 0.03MPa. When the oil return pressure exceeds this value, the oil return valve opens, the fuel injection pump and the extra diesel on the injection nozzle will flow back to the tank. If the spring tension is too large, the oil return valve will leak, and the excess diesel will flow into the cylinder and cause the mixing. Smoky smoke than misalignment. Two is excessive intake of carbon on the intake valve, affecting the intake of normal air volume, resulting in too much mixed steam. Considering that the vehicle has just been overhauled, the carbon deposition factor can not be considered. The three is that the gap between the valve feet is too small, which leads to the obstruction of the gas and even the phenomenon of gas flow reversing. The gas flows back into the air filter and enters the gas to strike, forming the similar noise similar to the drum. The malfunction that you described is abnormal, so the reason for my diagnosis is that the valve foot clearance is too small. It is recommended that the valve foot clearance should be re inspected and adjusted according to the following steps, which should be able to troubleshoot. (1) rotate the crankshaft to make the piston of the first cylinder at the top stop point of the compression stroke, and adjust one cylinder intake and exhaust valve, two cylinder intake valve and three cylinder exhaust valve. (2) insert the valve tappet into the cam with a feeler, and the value should be 0.5mm + 0.05mm. The size of the gap can be adjusted by different sizes of valve spacers. (3) adjust the method: turn the tappet, so that the notch on its edge is aligned to the side of the intake and exhaust pipes. Press the tappet down to the lowest position and use compressed air spray gun to spray compressed air on the tappet notch to make the adjusting shim float and remove the adjusting shim with a clamp. (4) the thickness of the gasket needed when the clearance is 0.5mm + 0.05mm is calculated on the basis of the measured clearance and the thickness of the adjusted gasket taken out, and the new spacers with suitable sizes are replaced. When installing the valve clearance adjusting shim, the side with the thickness value should face the tappet. (5) the adjustment is finished, the crankshaft is rocking, the fourth cylinder is in the compress stop point, and the four cylinder is treated in one cylinder, that is, the four cylinder intake, the exhaust valve adjustable, the three cylinder intake door adjustable, the two cylinder exhaust valve adjustable. (6) after the two adjustment of all valves, a re examination should be carried out conscientiously. The thickness of the valve clearance adjusting shim is generally 3.25 to 4.90mm (the increment is 0.05mm).