I'm with the previous post...check the compression. My son's '88 had much the same experience. We verified fuel pressure at the rail with a gauge, verified spark by pulling a plug and watching it, verified injectors firing with a noid light, then checked compression on a couple of cylinders...found it to be lower than I like. Then I remembered a trick a REAL mechanic taught me in my college days of part time work at a service station...
The mechanic taught me that when lots of cranking yields no start, often times the unburned fuel washes down the cylinder walls, removing the thin coating of oil that assists with achieving good compression. Not only that, but the unburned gas also gets into the oil sump, further reducing the ability for the oil to assist with good compression.
Well, long story short...we did an oil change, put a little bit of oil in three cylinders to assist, and I'll be damned if the thing didn't start right up!
You might want to pull your oil dip stick and give it a smell. If you smell gas, change the oil and then try to start it up.