The oil pump is easily removed once the flywheel housing has been detached from the engine/transmission unit as detailed previously.
Knock back the locking plate tabs and remove the pump retaining bolts and locking plate. The pump can now be withdrawn together with its gasket .
On 1275 GT models, the pump is of the 'star-drive' type and the splined coupling will either be removed with the pump or left in the end of the camshaft. In the latter case, the coupling can be easily withdrawn if required. Other models have a 'pin-drive' type pump and no separate coupling is used.


Install the pump in the reverse order of removing. Use a new gasket and locking plate. Ensure that the pump inlet and delivery ports are not obstructed by the gasket when fitting.
On models with the 'pin-drive' type pump, align the slot in the end of the pump drive shaft with the pin on the camshaft before positioning the pump on the cylinder block. Ensure the pin engages correctly with the camshaft.
On 1275 GT models, fit the coupling on the pump drive spindle before positioning the pump on the cylinder block. Again ensure that the coupling engages correctly with the camshaft.


The oil pump may either be of Hobourne-Eaton or Concentric Pumps manufacture. The overhaul procedure below applies only to the Hobourne-Eaton unit, as the latter type is serviced as an assembly only .
In most cases of wear or damage to the components of the oil pump, it will be more economical to obtain a complete new pump rather than to obtain new parts and repair the existing unit. The pump should be dismantled and inspected to determine its condition as follows:-
Remove the screw securing the cover to pump body and detach the cover. Note that the cover is also located by two dowels on the pump body. Withdraw the rotors and the pump drive shaft from the body.
Wash all parts in solvent and dry thoroughly. Use a brush to clean the inside of the pump housing. Ensure that all metal particles and dirt are removed.
Inspect the inside of the pump housing and the rotors for damage and signs of excessive wear. Inspect the inside face of the pump cover for scores, grooves or other signs of wear; if present, the cover must be replaced.
If the pump appears satisfactory, refit the rotors in the pump body, ensuring that the chamfered edge of the outer rotor enters the pump body first.
Check the clearance between the lobes of the inner and outer rotors . The wear limit is 0.006 in (0.152 mm).
Check the clearance between the outer rotor and the pump housing. The wear limit in this case is 0.010 in (0.254 mm).
Check the rotor end-float by placing a straight-edge across the face of the pump body, and measuring the clearance between the straight-edge and the end of the rotors. The clearance must not exceed 0.005 in (0.127 mm). If the end-float is excessive, but the other clearances are within the wear limits, the pump face can be carefully lapped on a flat surface, after removing the two locating dowels, to bring the end-float within the limit.
If the components are in satisfactory condition, reassemble the pump. Lubricate the rotors and pump housing liberally with engine oil before fitting the pump cover. Finally, check the pump for freedom of action.