Make sure there are no leaks or ways for air to get in the intake side.
Bad accelerator Pump? Bad float? Wrong, fuel pump check valve. new fuel pump is on order, or add a check valve.
The most probable cause for a pump losing vacuum would be a cracked gasket, or perhaps a crack in one of the hoses.
check fuel pump fuse..
No, you do not have to prime the oil pump.
you dont need to prime the pump
Did you "RE-PRIME" the pump after you changed the pressure control switch? A likely reason you are not getting water would be that the pump "PRIME" was lost when you changed the pressure control switch. Pump seals can be burned up quickly if you run a jet well pump with no prime (lost prime) and will cause them to leak around pump shaft.
Yes it could. It would depend on it's application, where it is in relation to the pump and the type of pump and system you have.
either your oil pump screen is clogged or you need a new pump
Turning the key to only the on position, the pump will only run for a couple of seconds to prime the system. Turning the key on and starting the engine, the pump will run and keep running as long as the engine is running.
There is a hand pump under the bonnet, black in color Your thumb would fit on it. Keep pressing down till it becomes near solid, then you have primed it.
A weak or worn-out pump or leak in the line
To prime the oil pump on most cars all you need to do is turn the motor over without it firing, disconnect the coil and turn the key, this will prime the pump.