ztw 2004 starter?

When it is failing, do a starter test. Your starter will have two wires, a big one (should have 12 volts) and a little wire (ignition wire). Have a helper crank engine when failing, the little wire at starter should have 12volts in the crank position, if it does and you have 12 volts on big wire at starter, and still wont crank, suspect faulty starter.