intermittent starting. spark ok. starter fluid works. cause?

No shit Sherlock! Gas in what? There's plenty in the tank, it's just not getting to the injectors. The starter fluid primes it & it runs fine; shut down, start up, no problem until the next time with no warning. As I said, it's an intermittent fuel problem. Any thoughts are appreciated.

Well there Watson.. When it will not start, be a damn good time to have a fuel pressure test guage hooked up so you can tell if it's an injector problem or a fuel pump/pressure problem! .. There are quite a few possibilities like TPS .. CTS .. ECM injector driver etc.. I wish I were able to tell you exactly what it is but my Chrystal Ball seems to be on the fritz.. I have to use a high end scanner, fuel pressure guage and a noid light for testing in these cases... Any trouble codes present?

Thanks pushrod. Good thoughts. No trouble codes. Trying to do elimination diagnosis, but don't want to just start replacing sensors indiscriminately. I especially like your etc. idea. Can I borrow your tester for that? I actually was hoping someone out there has caught this phantom & could identify it for me. Oh well, at least I have a good stock of starter fluid. P.S. If you send me your Crystal Ball, I'll polish it for you. Mine's cracked.

If you don't have easy access to a fuel pressure guage.. Rent one from parts store.. Hook it up and configure it so hood can be closed and guage can bee seen..then drive the car and note fuel pressure reading at each start-up... I think you'll see a lower pressure reading when it doesn't start.. A code reader (scanner preferred) with live sensor data would be extra nice so the TPS (throttle position sensor) reading can be monitored as well which is equally important! .. That's the only way you're going to find this problem without guessing at it!.. You can post test results for more info... Good luck!