First off, welcome to FTE and the Big Bronco Forum.
My first suggestion would be to check electrical connections. I know, I know, "but it tries to start sometimes". But if the weather where you are is anything like it is here, its so freakin humid that flash-corrosion occurs in hours rather than days or weeks. Enough in the right (or wrong as the case may be) places can let it start but vibrations will work things loose in a hurry.
If that yields nothing tangible and the problem persists, run a KOEO test first and see what the computer says is ailing it. If there are no codes present or you get a 11 or 111 then move on to a KOER test... the tricky part with the KOER is getting it started and keeping it running long enough to get to operating temp BEFORE you run the test.
On a side note, unless your '94 happens to be OBDII (which is rare if I recall), you don't need a decoding device any more complicated than a paperclip.
Check this out..
