Taurus SHO starting problems-HELP!!!!!

I have a 1990 Ford Taurus SHO. The other day it would not start after stopping at a mini market. I had to have it jumped and then they checked the battery and it was totalyl charged after driving it only 5 miles. Checked alternator and was just fine (which I had replaced approx 6 months ago). I then bought a brand new battery thinking it must be that since it was about 5 years old. Well, it did not start with the NEW battery so the guy cleaned the connections better and boom - it took off. It started every day with no problem for 5 days until yesterday when I stopped for gas and shut it off and it would not start (seems like it is only when heated up)... I had it jumped and it took right off. I shut it off approx 20 minutes later and it sat all night long and boom - it started right up this morning with no hesitation. I drove it 85 miles and shut it off and for fun tryed to start it right away after shutting it off and the same thing -dead! Please help! Any advise..... Has a new starter AND a new alt (probably they used a rebuilt one) but should not be that then. New battery now too so NOT that.... Any and ALL suggestions would be most appreciated. It doesn't make any sound when I turn the key when this happens. No clicking or sound at all - nothing heard. Very wierd............... HELP!!!!!!!!!!
Thanks

I'm having the same problem with my 1991 SHO. Has anyone been able to help?

DS

Both of you need to hook your cars up to Diagnostics systems, when SHO's start developing electrical problems, quirky ones usually, the culprit is an odd sensor, CPS, CKPS, TPS, the list goes on...

My local Ford dealer could not find the problem. I guess I'll have to take it elsewhere to find the malfunctioning sensor. Any other recommendations?

DS

Ground problem?

Whenever I had 87 octane in my SHO in hot weather, it would die. As soon as I got the 92/93 octane in it, had no problems. My guess was the anti-knock sensor was retarding the timing too much in that hot stop and go traffic with the cheap gas, because it would never do it for the dealer. Though I've read several articles saying that the Ford test guys would run them in the desert with 87 octane with no problems, there would be a side note saying they would disable the anti-knock sensor to keep it from retarding the timing. I don't know if that was your problem, but you might want to try and remember what type of gas you put in last before the problem hits. (Back in the late 80's I worked at a gas station that put 87 octane in all 3 underground tanks, so be wary of those no-name gas station's also! I didn't work there for long, they tried to cheat the employees as much as the customers.)