Read the Fuel Supply System Guide.
Until the ignition system and fuel supply system is good, you're wasting your time trying to start the engine. And in fact, may be damaging your injection pump by pumping a lot of particulate matter into it. The Spica pump section is very dependent on clean fuel . . . hence the TWO fuel filters.
If you have an original fuel supply pump, I can almost guarantee you that it's unserviceable, especially if it sat derelict for years. I would not trust an old OEM pump. In fact the entire fuel system, tank to engine and back needs to be inspected and cleaned. One of the surest ways to wreck a Spica system is to leave it derelict, although 6 months isn't too bad . . . rusty fuel tanks, clogged fuel filters, gummed/varnished up fuel supply pumps, front fuel filters/pressure relief valves, and injection pumps.
You can use an inline gauge (between the front fuel filter and the injection pump). With the engine off you'll get a steady reading. With the engine running, unless the fuel pressure gauge is dampened, you'll likely see wild pressure fluctuations due to the pumping action of injection pump itself. Depending on the gauge, you might be able to make out a "mean" reading. The salient fact is that the low pressure warning light needs to be out, indicating >7 psi. Normally, I like to see 10 psi with the fuel supply pump running on only battery (12v) and 13-15 psi with the engine running and alternator supplying around 14 volts. The supply pump is VERY sensitive to voltage in how much pressure it puts out. That's why it's very important to have excellent electrical connections to it (both power and ground connections) with no line voltage loss.