Gary's right, most likely dropped a leg somewhere.
If you have a traditional pump (since it's 8 years old, this is likely true), then it's got all it's start/running stuff built into the motor casing. The start capacitor is in the motor. However, if you have an old system with a "new" non-capacitor pump, as it could have the start capacitor in a control box topside. I doubt this, but it's possible.
The following info is applicable to a 220v single phase system with a traditional self starting permanent capacitor encased motor. This represents the vast majority of the market over the last 20 years or more. LEGAL DISCLIAMER: However, I make no assurance. You need to verify what you have before you assume anything. If you're not sure of what you're doing, get a licensed electrician or plumber.
There are a few things you can easily check to start the troubleshooting.
Be aware that wiring colors can sometimes vary from location to location, state to state, etc.
White is almost always considered "neutral".
Black is typically "power".
Bare copper wire is "ground".
Yellow or Red can sometimes be used as an alternate to black; i.e. you'd have one black and one red, rather than two blacks for power.
The point to understand is that to get 220v, you use both sides of the single phase power. To get 110v, you only use one side and a neutral. It's not uncommon to see long runs of wire be joined by different colors. You might see red connected to black or yellow. Hope this makes sense.
First, check supply voltage at the panel box; I assume it's a 220v system. You should have 220 across the two hot phases, and 110v from each side to neutral.
Then, check to see if you have that same good voltage at the pressure switch supply side. (I think this is what you're calling the "relay" but techinically, there is no realy; it's a switch with contacts, closed/opened by pressure). It is typically on/near the blue pressure tank. There should be a small diagram inside the lid to show wiring. Don't get confused by the wiring. Sometimes the supply voltage is on the outer contacts (1,4), sometimes the inner(2,3). Sometimes it is alternated in positions 1,3 or 2,4. Doesn't really effect how the thing operates, but just be aware you may have to figure it out. You want to check the supply voltage with the power on, but the pump not running (no demand for pressure). You should still have 220v supply at the switch.
If you have good voltage there, then have someone help you from this point. Run out to the well head and, with the power off, disconnect the power leads from the motor leads going down into the well. Then have your helper turn the power back on, bleed off some water in the house to make the pressure switch call for pumping, and once the contacts are made, you should have 220v at the power leads out at the well head. You should have 110v from each power lead, when checked with the neutral wire. In simple terms, you should have 220v across black to black, but 110v from each black to white.
If you have 220v at the well head, there is one more check to do. You need an ammeter to check running current. Turn off the power, hook all the connections back up, turn the power back on, and have the pump run again. Check for amperage on both the "hot" lines. Each one should have a roughly equivilant amp draw. They may not be exact, but they should be close. Depending upon HP rating of the motor and depth of pressure head (well depth), it could be as low as a few amps, to maybe as many as 8 or 10 per side. The important thing is that they should be nearly the same (within an amp of each other or so).
If you have no supply voltage to the well head, it's time to start looking for broken lines somewhere in the house or underground. It's very unlikely that the line actually broke in the well shaft, unless the lower fitting is loose and the motor has torqued itself around and pulled on the wires, which is RARE.
If you have unequal running amps, it's time for a new well pump.
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The blue tank is an accumulator. It keeps the pump from running 100% of the time during water demand. It stores pressure and water. It is typical to see it run from 30-50psi, or from 40-60psi, depending upon setpoints. It's a very important piece of the system.
