Changing Oil Pumps and Filters
Never jump into your car, start it up and drive off fast. Always give the engine half a minute before driving out of the garage and then drive slow until it's hot.
New oil pumps need to be primed so they work. When replacing an oil pump, or even when refitting the old one that is still in good working order, the oil pump will not pick up oil from the sump unless it is already wetted with oil. The oil is necessary to seal the pump and allow it to suck up oil from the sump and then pump it through the oil galleries.
Problems can occur too when the oil pick-up pipe is not airtight where it fits to the pump. Where the pump fits to the block also needs to be airtight and fitted squarely. If these points are not airtight then air will be mixed with the oil resulting in low oil pressure and oil feed through the engine.
If you've been working on your motor, after refitting your oil pump, do not start the engine until the oil pressure light has gone out. Bearing damage occurs in the first few seconds a while idling without oil pressure, even if the bearings were prelubed during assembly. The damage once started in this way will develop to eventually cause engine failure. The bearings are usually blamed in these instances, and it is always the big ends that suffer.
MGAs and MGBs up to 1968 tend to empty the oil filter canister when the motor is stopped. On these and all 68-70 MGBs with the vertical element filter, which always drains empty, it takes a few seconds to fill and get oil pressure on start up. Therefore it is vital on these models to follow the advice in the opening paragraph. You should also check that the steel filter locating washers are still there – one at either end of the filter. The top one is fixed to the adaptor and the canister washer is on the bolt after the spring - they get thrown away because they have stuck to the filter.
If you have a spin-on filter and the oil pressure takes a while to build up, it is likely that you have either an incorrect filter or a faulty anti-drain valve in the filter. If this valve is not working then even the oil cooler is syphoned empty! Some garages and Fast-Lube places tend to use any filter that screws on. I have rebuilt three motors ruined by the incorrect filter.
Here's wishing you happy, safe motoring, Regards,