If engine will not turn over, take each sparkplug out and inspect for water in cylinder. You could have a cylinder full of water (hydrolocked) - possible cause head gasket failure. Of course, engine could also be jammed because of a frozen starter, but that is not very common. And it could be jammed because it is siezed (oil failure at critical points) [all too common]. Should be able to turn with breaker bar on crank pulley bolt with plugs out. Go ahead and drop belt off at this point for testing.

 

Nope!
I had a mechanic look at it he said its the oil pump that needs to be replaced, we will see if it starts after that or not.

 

The problem is if the engine is seized because of oil pump failure, then there is no point in putting on another pump. I can't imagine any situation where the broken gears in the pump could keep the engine from turning, unless the engine seized up because of the lack of oil flow. You could pull the timing cover off with the pump in it and then try to rotate engine but, I would be shopping around for a new engine. There have been cases were the gears in the pump have bound up enough to blow out through the front cover but, if that kind of binding had taken place I would think thats what you would be seeing.

 

Here's a pix of a cracked oil pump. Even when broken, they still rotate, can make a ticking noise, and produce enough oil pressure to turn off the oil warning light (about 7 PSI). Problem is that they don't make enough pressure to operate engine correctly, which is 50 PSI at 2000 rpm when engine is warm.

Oil pump is pretty tough, compared to bearings that are starved for oil.

Please post pictures if you can of your pump pieces the mechanic finds. If oil pump failed, and vehicle continued to be driven, pirece by piece repairs to engine are going to exceed price of a used or rebuilt engine in many cases.