Compression should be OK if it starts cold, even if it doesn't do it reliably, compression is not a "come and go" thing.
That's the first of the big 3 for a running gas engine
1. compression
2. spark
3. fuel
If you add fuel to the intake and engine doesn't start then spark would be lacking.
If you think there is spark then spark can be weak so cold engine start would be marginal, or spark could be at the wrong time.
A timing light used while cranking can tell you if spark is timed correctly.
'91 should have a TFI spark system these do had their problems after 20 years of operation, good read here on testing for a problem:
http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml
Fuel, as said above, can be manually added to the intake, if engine starts up and then dies fuel would be the problem.
Listen for fuel pump when key is turned on, it runs for 2 seconds each time key is turned on.
Turn key on then off a few times, this builds up pressure in the fuel rail.
Fuel pressure regulator(FPR) on the fuel rail can fail, it gets stuck open, so fuel system pressure is lost after a few seconds, engine starts then dies.
FPR is connected to the fuel return line, remove this line and turn key on, no fuel should come out of FPR, if it does then replace FPR, it is leaking.
Fuel pressure on '91 should be 35-40psi, that more pressure than most tires, on the fuel rail is a schrader valve(tire air valve), press on the center pin and fuel should squirt out 30ft, 35psi is alot of pressure.