HARD TO START IN MORNING

ok,
all fuses good.
glow plugs test okay.
all filters good. fuel and air
fuel pumps all primed.
try test fuel? using a spray bottle with diesel in it ,past air cleaner point. if that works (runs)for say 3 seconds, the injectors are not injecting fuel.

ok no engine stated?
if gas engine, ?
I bet never tuned-up up in decade,right?> that gets 99% here.
but it can be far more complex, not guessing,,
what if , the ECT reads wrong.
and the PCM thinks you are in ALASKA,and you are in key west,FL..
so,it floods cranked. and cold running,same...

all EFI cars do that ,everyone, like that.'

forget heater (that blow'r motor sucks 15amps and alternator puts that load on the engine, breaking the CAMELS back, for get that
fix MISFIRE COLD that is the problem.!! real.

and new spark plugs top that list????
a rich engine needs more spark, and on HILLS

and scanning the ECT.
does ECT read correctly first thing in morning before starting engine
yes ECT can be scanned keyon, not started.

correct means if last night was 40f, the ECT is 50f in morning
or lower. say 41f.
-20f wrong, 0f wrong , got that? not blow average of last nights
ambient air temps or garage temps parked. there.
the air cleaner can be packed.up
the ISC valve stuck (my 4.0L did that ever 10k miles)most of the cured in 90s with better ISC
leaking injectr.
misfiring cold
and more
best is a tuneup ,pray, and work form there.
doing tests.

Usually check timing after dart and fuel check.

Your Idle Air Control Valve has gotton Carbon Build Up and needs to be cleaned. 75% of the time, you can clean them and they will work immediately but 25% of the time, you have to replace them but the IAC (Idle Air Control Valve) is the same as a CHOKE on older cars... and it is just not adjusting the Fuel/Air Mixture correctly

I had the same problem and it was a vacuum leak in the PVC hose. It's hard to track the vacuum lines, but if you take it into local mechanic they can do a "fog" or "smoke" test they call it, and if you do have a vacuum leak it will show up. My car was doing same thing and it was the PVC hose, which is hard to see & hard to get to. $200 parts and labor to replace and it was fixed.

Could be a long list of things.
Weak spark, too much or too little fuel, etc.
You'll need to check the spark at the plugs and try spraying carb cleaner into the air intake to try to determine if it is ignition or fuel related.

check fuel line for minor leaks and check valve also check the filters sounds like air bound problems

Try plug wires, that's about all you haven't replaced. Actually if you have an ohm meter you can test them - anything over 6k ohms per foot - REPLACE them. Also run a good fuel system cleaner through it and stay away from cheap gas.

Change the coolant temp sensor.The sensor could be sending warm up signal,all the time.

remove the air filter housing from the throttle body, or if its mult-ported injection, remove the large air duct. Do this the night before. The next day, before cranking and having a spray can of carb. cleaner, spray a couple of shots of carb cleaner either into the large air duct, spray towards the engine, or if its single body injection, spray directly on to the throttle body.

Crank engine immediately, preferrably have some one else sitting in the car to start it after you spray.

If the car even tries to start, replace cold start relay.