1. Remove the oil pan.
2. Loosen the two fixing bolts and slide the pump assembly down with suction tube and suction cup.
3. Place the oil pump on the table in the workshop, lift the cover with a screwdriver and wash the suction screen in kerosene. Insert the mesh back and press the cover.
4. Remove the two small screws and remove the cover from the pump housing. Check cover surface. As seen in the picture (photo 2.24) the gear train left marks on the cover. If the depth of these traces is significant, the surface of the cover must be ground. The gap between the teeth, the gap between the front surface of the teeth and the housing, or finally the gap between the side surfaces of the gears and the pump cover, cause a leak through which oil flows from the pressure chamber into the pre-chamber. Part of the oil instead of the oil line circulates through the pump. As a result, the performance of the pump is reduced (or the amount of oil supplied to the lubrication system), and oil pressure. The second parameter is very significant. At very low pressure, the oil film in the bearings may break, causing accelerated wear.
Therefore, if there is any doubt about the correct operation of the pump, it will be better and more economical to replace it with a new one. Re-extraction of the pump is an expensive operation, but if the liners fail, the cost of repair will exceed the price of a new pump several times.
5. Remove the gear train and wash the housing and gears in clean kerosene. Dry and assemble the transmission, lubricating with clean engine oil. Measure the gap between the gears with a feeler gauge, the so-called gap between the teeth (photo 2.25). It should be between 0.05 and 0.20 mm.
6. Place the guide plate on the pump housing and measure the gap between the gears and the guide plate with a feeler gauge. This gap between the side surfaces of the gears and the pump cover must not exceed 0.15 mm.
7. Measure the gap between the top of the gear tooth and the wall of the pump casing with a feeler gauge. This gap should not exceed 0.25 mm. Usually, if this gap is larger than permissible, this indicates wear on the bushings in which the pump drive shaft is located on the bearings. If the gap in the bushings exceeds 0.20 mm, the pump housing must be equipped with bushings.
Usually, if something in the pump has worn out, especially the gears or the housing, the entire pump must be replaced. If wear is within acceptable limits, the pump is assembled and installed on the engine.
Installation
8. Before fixing the pump, check that the working surfaces are clean. Then insert the pump into the hole and tighten the fixing bolts with a certain moment.
9. Put on a new oil pan gasket, but do not use sealing material (as it makes it difficult to detach from the hull during the next repair). Fasten the oil sump and tighten the evenly fastening bolts.
10. Install the oil drain plug with a new o-ring.
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