91 GA cranks but won't start

I really need some ideas on my 91 grand am w/ 2.5 engine. My wife was coming home with on the hiway and she said it just keep losing power and then she pulled over and it died. Got it home and could hear the fuel pump running and had fire at the plugs. Changed the fuel filter and it seemed restricted. But still didn't start. Checked the TBI and could see fuel but no a good spray impulse. Checked the fuel pressure and only had 28 psi. Haynes manual said was suppose to be upwards of 40 psi, so I figured it needed the fuel pump changed. Did that, still didn't start, but had good pressure and great TBI spray! Then I thought maybe the ignition was maybe not real strong as it didn't seem to shock me that bad when trying to check it again and the spark seemed kind of purpleish and not a strong white fire to it. So I changed out the coils/module/cranksensor assembly with one I had for my daughter's '90 Skylark with the same engine awhile back that was good, but still never started. I don't see any bad fuses. Best I can figure I got good fire and fuel but it just won't even consider starting up. I hate to think that somehow the timing chain is out of time, but it doesn't act at all like it could be as no back fire thru anything or hard cranking at times like you'd expect on something like that. It had run great (except I was still in search of the mysterious oil leak I had sought ideas on sometime back) and got 30 mpg. Am I forgetting to check something obvious? Or any other ideas before I dive in on the timing chain? All help would be greatly appreciated! thanks everyone!

timing chain and gears is the worst case scenario.
have you checked the connection to the MAP sensor?
have you pulled the vacuum lead to the EGR?
an EGR that loses its spring (weakens in vacuum operation), can weaken the combustion, and rough idle/stumble conditions will generally occur.
an EGR locked open, or burnt out, allowing excessive air flow through it can kill the engine right after cold start and/or warm-up, or surge and run rough during idle and cruising speeds.
no EGR (clogged) can cause high idle/revs and higher coolant temps, higher combustion temps, and engine knock/detonation.

or is the '91 got an IAC motor? might pull it off and rap/tap all the carbon deposits out. you never mentioned mileage?
battery is fully charged? plugs have been changed recently?
timing chain is like THE LAST item on troubleshooting steps...
a timing chain can go at 120K, but I've seen them go for 300K before flapping around loose in the cover. I've even seen a 327" chew through the cover, and the chain at idle would slap/fall partially out of the timing housing, and then, jump back on those gears at 5500RPM and run like nothing was wrong at all, until you got back to idle (or almost idle).

unplug the MAP and see if the vehicle will start. if it does, definitely replace, if not the MAP can be checked at local AutoZones, or with a multi-meter:

three terminals at the plug housing may be marked A,B,C; if not, A will be the one closest to the edge of the MAP body, and C will be the closest to the inner/center of the MAP housing body.

take some jumper wire (speaker wire, etc.) and jump the connection plug terminals A & C to where they would plug on the MAP itself (leaving only the middle terminal (B) on the MAP open.
turn ignition on, but DO NOT START engine!
set multi-meter to 20V setting and connect POS(+) to terminal B, and NEG(-) to ground.
reading should be between 4.5 and 5 Volts.

hope this helps,
chris
nrt racing

Another thing to look into is your ECM/computer. When that goes out you can get similar issues of starting. Mine went out several years ago, and stumped our mechanic, because the car was getting fuel and spark just wouldn't turn over.... Apparently the computer was telling all the compenents to go at once instead of insync... causing the engine to flood itself out and not to start.... just another thought..... If the timing went out, she should have gotten a Check engine light prior, if that came on, have the computer scanned for codes... Good luck

Do a compression test before you start on the timing chain, that will tell you if you have a problem with the timing chain off a tooth, broken, or if everything is normal. Also on a 95 (which is what i have) if the computer turn on the check engine light will come on when you turn the key on, I don't know if thats the case for yours or not.