Hi Lee
I presume that it's the motor stopped which is the fault. I run a shureflo 100psi too. More often than not it's the rectifier that fails (the electronics in the "bell end" of the motor with the carbon brushes.) If you're lucky, a new bell end assembly will repair your pump for probably about £25 to £30. This is a service component anyhow and I replace mine every 300 hours. If your machine has an electronic dial to alter the pump speed, these can fail too. I've by passed this on one of my machines as I never used the facility and it costs about £70 to replace. If a new motor is required, you may be able to buy the motor without the pump assembly (I know you can with a Flojet)
Safe and happy servicing:)
Ken