A crack in the pool pump can not be fixed permanently. Silicone and sealants may fix it temporarily, but it will need to be replaced.
NO
I general, the answer is yes. It the crack comes from the pool moving, and the gunite has cracked, then the gunite has to be repaired before the plaster. Sometimes opening up the gunite crack and refilling with concrete will answer the problem. If movement of the soil is the problem then that has to be fixed first.The soil getting excessivly wet and dry can mean that the pool will move, if it is only part of the pool then there will be a structuaral crack. Only opening up the crack will tell you whether it is a plaster crack or a gunite crack. A replaster is from about $2000 up and structuaral repairs from about $1000
Fixed
Yes, an in ground pool can crack during an earthquake if it is close enough to the earthquake.
is it on
You have to drop the water level below the piping of the pool, then take compressed air and blow out the lines, normally you disconnect the pump and filter and blow the water lines from the direction of the filter and pump back towards the pool cap the pool inlets and outlets, and put the pink R. V. anti freeze in the lines so that they do not crack.
Normally there are 2 baskets before the pump, One behind the skimmer and one on the pump. However If you only have the one basket then you will have rubbish caught in the impeller of the pump, You will have to take the pump apart and clean the impeller out.
Pool center has diagrams of different pumps and filtering sytems.
no
there is probably something in the pool that got into the pump
Yes, air can get into the pool pump causing it to lose prime if you have a leak or crack in the plumbing leading from the pool to the pump. The pool level being too high plays no role, however you should make sure that the pool level is not too high for other reasons, mainly the level is too high, water will leak under your cement causing it to settle. Keep the water level in the middle of the skimmer opening.
I would think if the the crack is present only in the plaster, and not the tile, it may be surface. If, for instance my pool, has a cracked tile and the crack is extended down the side of the plaster, it is structural.