[papajam]

There's no need to remove the Cold Start Solenoid (CSS) to test it. Actually, it can't be removed by unscrewing it anyway as it is mechanically attached inside the injection pump.
To test the solenoid, warm the engine to operating temperature (175F minimum). Disconnect the wire on the top of the solenoid. Now, with the engine idling, momentarily connect a jumper wire from battery positive to the top of the CSS and observe two things; one is a click (or a clunk) from the solenoid indicating that it works and two; that the idle speed drops about 150-200 RPM.
If the engine stalls when the CSS is engaged, the mixture is too rich. Loosen the locknut at the base of the CSS, turn the CSS clockwise and retest. If there is no change in idle speed when the CSS is engaged (AND the solenoid clicks), the mixture is too weak. Loosen the locknut at the base of the CSS, turn the CSS counter-clockwise and retest.
The CSS is but one component needed in the Spica fuel injection system. If you send me your email address in a private message, I'll send you a 10 page pdf document that guides you through the setup procedure without the need for special tools.