"Cycling" in a pressure system is generally when the pump is turning on and off too quickly. Pressure systems are specifically designed so that the pump runs up to its maximum pressure, then you use water from the pressure tank, until it reaches the minimum pressure, at which point the pump turns back on and runs until it reaches the maximum.
The recommended minimum run-time for a 1-2HP pump is usually 2 minutes. How you get to that is based on the flow rate of the pump, and the size of the tank.
Based on your 150gallon tank, and not knowing your flow (in gallons per minute, GPM), based on this tool here's some example flows/times:
- 16GPM: 3 minutes
- 20GPM: 2.5 minutes
- 24GPM: 2 minutes
As you can see, the higher the flow rate, the shorter the pump will run.
In your case, it sounds like one zone is basically matching the flow rate of the pump (you could verify this by watching the pressure gauge while it's running, it should be fairly steady). While this may reduce pump starts, if you use water elsewhere at the same time, your pressure will drop and the pump will not be able to keep the pressure as high.
Now, the flow rate the pump puts out depends on a couple things, most importantly: the pump itself (and now many stages it has), and the depth to the water level. Each submersible pump will have a chart showing the flow rates at different depths, so you'll need to find your model and the water level to figure this out. Here's an example though, using a 2HP pump I found while running at 60psi (depth to water: flow rate):
- 20ft: 23.9 GPM
- 60ft: 22.7 GPM
- 100ft: 21.3 GPM
At first glance, this seems fine. My guess right now is that your first zone matches the flow rate of the pump, while the second zone is simply a lower flow rate than the pump. It's no problem, things are designed to work this way.
If you really want to reduce the cycling, you can hook up a bigger or a second pressure tank. This will give you more capacity, and so the pump will run longer, but it will also stay off longer while you use water stored in the tanks.
Now, if you had fast cycling (eg, <2 minutes run time) or "rapid cycling" (a couple seconds of runtime), then that would indicate a problem with the pressure tank. Normally the tank should be pre-pressurized at 2psi below your cut-off (low) pressure point - so in your case 43psi. To check this, you'll have to turn off your pump and let the water drain out (open a tap somewhere). You can top it up with a normal air compressor.
Best Answer
If the sprinkler controller can cause that zone to start dribbling then the solenoid is fine. (Note that "solenoid" is just one part of a complete valve.)
Do an experiment to figure out whether you have a broken pipe or a malfunctioning valve. For example, turn on one working zone, then (at the same time) turn on another working zone. (You may have to operate the valves manually rather than using the timer/controller.) Notice how much the spray of the first zone drops when the second zone comes on. Turn off that second zone, and while the first continues to run, turn on the malfunctioning zone. Does the spray of the first zone drop again? If it does then water in your malfunctioning zone is going somewhere, but not out the heads -- you'll have to locate and repair a broken pipe. But if the spray level of the first zone does not drop, then the valve of the malfunctioning zone is not opening as it should.
If you conclude the valve is malfunctioning there's a chance it could be caused by debris (a grain of sand, a small weed seed, etc) lodged inside. This could happen even on a drinking water system, but it's less likely.
I suggest that you consider how you would go about replacing that valve, have the required supplies on hand, and then try carefully disassembling the existing valve. Start by fully unscrewing the solenoid, and if there's no debris found there, take off the top of the valve. After cleaning it out, reassemble and test.
If things go well the valve could work normally again. If things go badly.. you're already prepared to replace the valve, so go ahead and do that.