Withdrawal
Remove the oil pan (see Section Removal and installation of the oil pan).
M10, M20 and M30 engines
1. On M10 and M30 engines, remove the three bolts securing the pump mechanism to the front of the pump.
Some models have only one central nut securing the mechanism to the oil pump.
2. Unscrew the oil pump from the cylinder block and remove it. On M20 engines, the oil pump is bolted across the cylinder block to both sides towards the front of the engine
3. On M10 and M30 engines, the oil pump is bolted to the front and center of the cylinder block
4. On M20 engines, the intermediate shaft drives the oil pump drive shaft, which in turn drives the pump. To remove the drive shaft, remove the retaining plate from the block and remove the plug. Check the condition of the O-ring and replace it if necessary. Remove the drive shaft and check both gears for signs of wear and damage and replace if necessary. The intermediate shaft gear in the cylinder block is indicated by an arrow.
5. If the intermediate shaft gear is worn, or the intermediate shaft bearing is worn or damaged, the shaft must be removed. Remove the engine (see part Engine Component Overhaul Procedures), then remove the timing belt, crankshaft and countershaft sprockets (see Section Removal, inspection and installation of the distribution belt and sprockets of its tensioner), as well as the front cover of the engine (see Section Replacing the front seals). The intermediate shaft can be removed from the front of the engine.
M40 engines
1. Remove the distribution belt, as described in Section Removal, inspection and installation of the distribution belt and sprockets of its tensioner.
2. Remove the cylinder head as described in Section Removal and installation of a head of cylinders.
3. Loosen the nut and remove the timing belt tensioner from the front end cap.
4. If necessary give screws of adjustment of backlashes from the block of cylinders.
5. Loosen the crankshaft hub bolt while holding the crankshaft stationary. This bolt is very tight and therefore it is important not to let the crankshaft rotate. It would be best to bolt a metal gate to the sprocket, you can also remove the starter and hold the flywheel with a wide-blade screwdriver. When using impromptu methods to hold the crankshaft stationary, be aware that there is the potential for damage to surrounding components.
6. Remove the sprocket and spacer, noting that the spacer flange points inward.
7. Give bolts and remove stabilizing...
...and guide rollers from the front end cap.
8. Using a small screwdriver or similar tool, remove the key from the groove in the crankshaft trunnion.
9. Remove spacer ring from crankshaft.
10. Give fixing bolts and remove a forward end cover and the oil pump from the block of cylinders.
11. Note the location of the front cover bolts. they vary in size. After removing the cover, remove the rubber o-ring from the groove in the crankshaft trunnion.
12. Note the correct position of the stuffing box, then remove it from the casing.
Status check
Given that a failed oil pump can cause serious engine damage, we recommend replacing it every time an engine is overhauled, unless it is in excellent condition.
M10, M20 and M30 engines
1. Remove cover and inspect housing, gears or rotors and cover for cracks and signs of wear (especially where the gear or rotor comes into contact with other components).
2. Check the filter to make sure it is not clogged or damaged.
3. Lubricate the gears with clean engine oil, then install the pump cover on the housing and tighten the bolts evenly and securely.
4. Before installing the pump - new, overhauled or old - check its operation on the engine. Fill a clean container with fresh engine oil of the recommended viscosity to about 2.5 - 3 cm.
5. Immerse the oil pump inlet in oil and turn the pump drive shaft counterclockwise by hand. When the shaft is turned, oil should flow out of the pump outlet.
M40 engines
1. With the front end cover in place on the workbench, loosen the bolts and remove the cover plate so that the oil pump rotors are visible.
2. Note the position of the rotors, then remove the inner rotor from the casing...
...and the outer rotor of the oil pump.
3. Thoroughly clean the rotors and shroud, then install the rotors in the previously noted position. The inner rotor should be installed with the guide facing the housing.
4. Using a feeler blade, measure the clearance between the oil pump housing and the outer rotor,...
...then check the clearance between the outer and inner rotors.
5. If the clearance is not the same as specified in Table of sizes and adjustment data at the end of the manual, the entire oil pump as well as the front end cap must be replaced. If the gap is within tolerance, remove the rotors, then pour some engine oil into the casing. Mount the rotors and rotate them to spread the oil over their surfaces.
6. Install cover plate and tighten bolts to specification.
7. To check the safety valve, remove the circlip...
...and remove the bushing...
...spring...
...and a piston...
8. Check if the length of the spring matches the value specified in Table of sizes and adjustment data at the end of the Guide.
9. Reassemble the relief valve in the reverse order of removal.
Installation
M10, M20 and M30 engines
1. Make sure that the mounting surfaces are clean and insert the pump into the special recess on the cylinder block. Fit the bolts and tighten them to the required torque.
2. Install in reverse order
M40 engines
1. Clean the mating surfaces, then install the front end cap and oil pump along with a new gasket on the cylinder block.
2. Tighten the bolts to the required torque. Please note that two different sizes of bolts with different tightening torques are used here.
3. Install the spacer ring on the front of the crankshaft.
4. Apply engine oil to the lips of the new oil seal, then press the oil seal into the housing at the previously marked location. Use a large wear head and crankshaft pulley bolt to install the oil seal evenly into place.
5. Install the key into the groove in the nose of the crankshaft.
6. Install the stabilizer roller on the front end cap and tighten the bolt.
7. Install sprocket, spacer and crankshaft pulley bolt. Tighten the bolt to the correct torque while holding the crankshaft stationary using one of the methods above.
8. Install the timing belt tensioner, but do not tighten the bolt yet.
9. Install the cylinder head as described in Section Removal and installation of a head of cylinders.
10. Install the distribution belt as described in Section Removal, inspection and installation of the distribution belt and sprockets of its tensioner.
11. Install the oil pan (see Section Removal and installation of the oil pan).