Shallow Jet Pump won't shut off

I have a 3/4 hp Sears shallow jet pump attached to timers that I use to water the front and back yards. I changed the pump last year so its relatively new. Just recently I've had problems with it.

The problem is the pump just keeps running and running even when the sprinkler valves have shut down and I have to pull the electric plug from the socket to shut it off.

The foot valve into the well seems to be good. There doesn't seem to be any major leaks in the plumbing. The pump appears to build up the proper pressure. But for some reason even after the automatic sprinklers have gone through their programmed cycles, the pump continues running. The pump continues to run even when I operate the valves manually.

Any suggestions?

Is there a pressure switch on this pump, or is the timer supposed to shut it off?
If there's a pressure switch on it, then I'd say the jet is plugged, which means that the pump can't reach cutout pressure.
If the timer is suppose to shut it off, then I'd say there's a problem with the timer, or a relay is staying closed.
If the same thing happens when you manually open the irrigation valves, then It's probably the 1st problem I mentioned.
Ron

Does the system have a tank to go with the unknown pressure switch?

bob...

Yes, there is a tank.

There probably is a presure switch somewhere...I just don't know where (or even what to look for). The reason I think the pump has a pressure switch is because the pump used to shut down after it was charged up. I think the pump switched on when the pressure dropped below 30psi and cut off when it was charged up to 50psi.

That would be the standard way one would work.

Look for a little box about 3" X 5" or so that has wires going in and out of it from the electrical supply to the pump. It will also have a plumbing connection of some kind which let's it sense the pressure in your system.

bob...

PS: It wouldn't be a bad idea to put a gauge on the pump so you can tell us what the max pressure is.

bob...

Sears jet pumps normally have the pressure switch mounted on the motor itself, unless it was removed and remounted somewhere else.
I staying with the theory that the pump won't shut off because it can't reach cutout pressure, due to a plugged jet, or a leak somewhere.
Ron