Observation

Candidates’ responses to questions on eccentric vane oil pump were not adequate. However, some of them tried in attempting some of these questions. Sketches were not also done satisfactorily. The solutions to the poorly answered part of the question are given below

(ii)        How the eccentric vane pump operates
It consists of a spindle which carries two or four vanes and is arranged off-centered or eccentrically in relation to the surrounding case. The vanes may be spring-loaded to maintain contact with the case or rely upon centrifugal force.
Oil enters at the point where the volume in the chamber is largest and is swept around the case. As it rotates, the volume is reduced slightly and oil is discharged into the gallery through the outlet.                             

(b)        (i)         Causes of high oil gauge pressure reading
- Oil too thick or engine too cold
- Relief valve struck closed
- Oil ducts in pressure side of system partly closed
- Tension of spring on relief valve too high
- Faulty gauge

(ii)        Causes of oil pressure lamp remains switched on
- Faulty pressure switch

• Low oil level
• No oil in the sump
• Use of low viscosity oil