I have a 2002 duramax 2500HD. the garage replaced the glow plugs because it would not start. Left the garage with it got it home and it once again won't start. Runs fine once started, no smoking at all, no decrease in power, no hesitation once started.

Check spark plugs, leads, distributor cap & rotor arm, fuel pump, fuel filter, coil pack(s), relays, replace any items that are suspect IE Fuel filter which has probably not been changed since new even though they should be changed on all vehicles every 18 months, all of this can be done at home & will save you a lot of bucks in mechanic/garage fees,

just had this problem it was the PDM ended up replacing the glow plugs
best price and life time warranty for both was at Auto Zone recommend if you buy the PDM get the extension cable and move the PDM to a cooler location

The Duramax fuel filter assembly is bad about sucking air. Replace the fuel filter assembly. It comes with a new fuel filter.
I need some good feedback.

Does it have diesel?
Could be fuel filter or fuel pump.
Glow plugs?
Injectors? these trucks have been known to have bad injectors.
Possibly the oil pump, the injectors run off the oil pump.

You need new glow plugs. Im guessing you live somewhere kind of cold maybe. It starts just fine after running because the motor is already warm. Quick start will work.....or at least it did for me until I used one mornig and went to crank and BOOM. It blew my air filter case to pieces and caught the filter on fire. Starting fluid is not meant for diesel motors. If you cant afford new glow plugs what worked for me is turn on the key all the way but dont crank wait 10 sec then repeat a few times and it should crank unless its really cold out or the plugs are really bad. Trust me thats what it is. I replaced mine and now It cranks right up even when its super cold.

Actually GM gas engines are 1,3,5,7 on the left and 2,4,6,8 on the right.
The diesel engine is actually just the opposite. 1,3,5,7 are on the right and 2,4,6,8 are on the left

Probably got air the lines....bleed and it will likely start.

make sure you coolant level is topped up.this happened to me once.it was just low coolant not allowing enough to circulate thru the heater

check fuse and fuse link to glow plugs.

THE DURAMAX ENGINE INJECTORS GO BAD AND SPRAY TO MUCH DIESEL AND IT FILLS THE CRANK CASE UP 200 THOUSAND MILE WARRANTY COMMON PROBLEM DON'T DRIVE IT ANY MORE IF U HAVE BAD INJECTORS.