Hard starting, starts & dies. fuel press. is 38 psi. not losing spark when it dies. when stone cold it starts fine & will idle till first time you shut it off.

no car told maker or model or engine size.
there are lots causes that, hard starts
if spark good and strong and even HV spark wire sets fresh.
the short list.

1. bad fuel
2. too much fuel cranked and floods
3. IAC bad, idle air valve stuck and wants to flood cold.
4. cold idle is the big clue, where too low. IAC failing
5. EGR sticking open at idle. possible.
6. if you press gas Pedal, at 5% (about) and starts easy and likes that until it worms up that means the IAC is dead.
7. I stop here lots more, no car told.

all cars modern EFI is it EFI> have IAC and ISC valves 1 or both.
and if stuck idle fails. hot or cold.
no car told why post like that 100 year of cars and 10,000 engines.
????

IF YOU HAVE NO HARD START PROBLEMS, COLD OR HOT, I WOULD START WITH A PC SCAN FOR CODES, EMISSIONS TEST & FUEL PSI CK. IT COULD BE AS SIMPLE AS A VACUUM LEAK. THAN SCAN PC FOR CODES (TPS, IDLE SPEED SOLINOID. OR RUNS LEAN OR RICH- VAC LEAKS AIR/ GF, INJECTORS FUEL PSI ETC. START WITH THE BASICS. AIR, FUEL & SPARK/ TIMING. GOOD LUCK FRANK M

not much info to go on. more info would be helpful. for example does it run fine for a few then it dies. my guess is a fuel filter or pump. you can run it till it dies and then hook up a fuel gauge to see if it has any pressure. when they get hot thy will lock up. so if your suppose to have 50 psi. and it gets hot. you might not get 10 psi and it wont run with less then 30 psi if its fuel injected

First thing is to check the fuel pressure regulator it could be faulty then i would check the fuel pressure it should be 60-66 psi with the key on and engine off.If its below 54 psi i would replace it.

check for 12v constant at your fuel pump if you are not getting that replace your relay.
if you are getting 12 volts at your fuel pump the fuel pump is possible to run tuel it gets warm then shut down to a lower rpm I would then replace the fuel pump

What engine do you have? You could still hear your fuel pump running but if you haven't checked the fuel pressure you may still have a problem with your fuel pump. You should be around 38 to 44 PSI when key is turned on not running. Did you verify you are getting spark or is there nothing to the plugs? Your ignition coil resistance should be (cold 9000-15,400 ohms) Primary should be .36-.55.
Your pickup coil resistance depending whether you are California or excluding California
California is
cold- pick up coil terminals G1 & G- Ohms 125-200
cold-Pick up coil terminals G2 & G- Ohms 125-200
cold-Pick up Coil terminals NE & G- Ohms 155-250
Ex. California models
cold-Pick up coil terminals G+ & G- Ohms 185-275
Cold-Pick up coil terminals NE+ & NE- Ohms 370-550 ohms
You also need to check air gap between PIck-up Coil & Signal rotor
California is .008-.020
Except California .008-.016

Here are some of the suggestions from Mitchell books:
ENGINE CRANKS BUT FAILS TO START:
*Ensure proper spark exists from ignition system
*Ensure Fuel system performs properly (fuel pump, Fuel filter, Fuel injectors, fuel pressure regulator).
*Check engine compression, valve clearance, valve timing and timing belt (if equipped)
Check airflow meter or MAP sensor and wiring
*Check idle air control valve (if equipped) and wiring.
*Check circuit opening relay and EFI main relay.
*Check STA signal at Engine Control Modual (ECM)
*Check Engine Control Modual (ECM) and wiring.

Just having fuel is not enough on this engine, here are the spec's. Even 1 psi out of spec can cause a no start.

Fuel Pressure
Pressure 1 (PSI) Pressure 2 (PSI) Pressure 3 (PSI) Range Note Range Note Range Note 60.0 - 66.0 Y131 50.0 - 63.0 Y132 66.0 Y133 Y131: System pressure with ignition on (PSI).
Y132: System pressure while idling (PSI).
Y133: Fuel pump pressure (PSI) with return line briefly restricted.

Bad ground to computer or bad crank sensor

Need to get a scan tool and look at the data stream while it is running for alot more info.Also any trouble codes.Sounds like initially,the engine isn't getting any fuel.I would have a pressure gauge connected to the fuel rail on the engine,so i could monitor the fuel pressure while all this is going on.Items to look at on the data stream would be timing,what timing is the PCM commanding for the engine.Also,have you checked for continuos power feed to the coils during this no start condition,and fire at the plugs while cranking.You could possibly still have spark,but maybe it is extremely weak?I have seen bad ignition switches cause weird problems before too.Many things power up through the ignition switch,just a thought.Have also seen bad PCM's cause strange problems..38 volts is a little on the low side for GM.Usually see those at,at least .50 and up,and rise steadily while pressing the throttle,up to just under 5.0 volts.Potentiometer with 5 volt supply.Vacuum leak can be checked with engine running at a steady idle speed,spray brake cleaner all around the intake manifold and listen for engine speed change.

Check the condition of the wiring coming off of the ECM. at the fender. I've seen the wiring insulation rub off causing no starts.