Been running fine this weekend until just now. Parked for an hour, then a difficult crank followed by slower-than usual cranking and no start. I have fuel pump prime and fuel pressure at the Schrader valve. I am NOT seeing oil pressure at the gage during cranking. I can't remember whether or not I should be. I torqued the oil pickup myself when I rebuilt the engine in '17, doubt it would have just fallen off. Wondering now if the timing chain snapped.
It's easy and fun to jump to a conclusion, but review the basics to rule them out. Have you used up the battery? Is the tach moving up to 300 when you crank the starter? Is some wiring loose or corroded? Is the oil level OK?
[This message has been edited by Gall757 (edited 01-12-2019).]
I've left the car for the night. I didn't think to check the tach while cranking, yeah that would have told me if the ignition module is dead, but it's still cranking and it's a year-old Optima Red Top. It had just started fine 30 minutes before so I don't think wiring problems. I just put in a new distributor that came with a new module a year ago, so I doubt the icm is bad either. I reconnected all the plugs on top to make sure they were secure - coil, plug wires, tps, maf, dist, etc. Just had a new catback installed at Midas yesterday, so they were welding on it, and I changed the oil less than 300 miles ago.
If your timing chain snapped, Im sure you would hear some nastiness while cranking it. Take a jump box n some starter fluid. If it starts on the fluid you got no gas getting to the motor. If it doesnt- U have a spark issue. Wiggle your fuses n shake some wire harnessesesses, worked for ol shemmy many a time.
Year old battery means nothing and Do not trust gauges in the dash.
First Check Volts @ the battery. Then check volts at the starter w/ ground probe to starter case or engine block. Because Slow to crank is is very likely a "dead" battery, alternator problems and/or wiring to them.
battery charged should be ~ 12.6 to 13.6 volt battery bad or not charged < 12.5 v
Volts @ the starter should = or be Very Close to same volts @ the battery. If not then cables are bad or loose.
Check volts @ the starter trying to start is better but Do Not get under the car when you try to start. You might be able to check w/o getting under at all. Carefully use a meter thru driver side and trans on top or mayby use a stick to extent probe handle but GT body makes this harder and likely have to lay over the trunk. Probes w/ "alligator chips" may help because you don't have to hold them trying to start.
Can be the starter w/ problems but If you to run starter w/ iffy battery and/or cables then you can kill the starter.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
The battery is supplying adequate voltage to the starter, and the starter is turning over the engine adequately for it to fire. The question is why it won't fire. I'm going back over to check on it, and if it's still there I'll see if it's registering on the tach during cranking. Big question remains - should I expect to see oil pressure during cranking?
Unplug your coil and remove the distributor cap and see if the rotor spins while cranking (cam gear/oil pump drive). If you have the old distributor, you can remove the gear and use it with a drill to spin the oil pump and watch the pressure gauge with the ignition on. Or, remove the oil pressure sensor and see if oil shoots out, lol.
Does the Tach climb while cranking? It should. Do you have fuel pressure with the ign on? Codes? Spark while cranking?
[This message has been edited by ZCR1 (edited 01-13-2019).]
Yeah I know, that's what concerned me about it... but it drove fine all day Friday and Saturday before this happened. I've got tools and am checking it over now.
Just FYI, the oil pressure sender does not act as a fuel pump kill switch. That's a common misconception. What it actually does is act as a backup for the fuel pump relay. Since the fuel pump is priming, the relay is good. Therefore, the function (or lack thereof) of the oil pressure sender doesn't matter.
When I tried to start it again the battery was so low that it wouldn't crank at all. Jumped it from my girlfriend's car, and it started up just fine. That Optima was just plain weak, so I had it tested and it failed. I swapped it at a nearby Autozone for a fresh one, as it was still under warranty. It was cranking, but not fast enough to fire. TheOgre definitely had a point, and for me, sometimes knowing too much isn't such a good thing. Thanks to everyone for your suggestions.
Just coincidence... or not? 
