Chevrolet Repair: 99 tahoe hard start when cold, 99 tahoe, hard start

Question
Hello, question has probably been asked many times before but here goes....1999 tahoe 4x4, 5.7 gas engine, 116 miles,new fuel pump, new filter recent (20K) tune up.   It WILL NOT start after sitting overnight unless few drop off gas (or starting fluid) placed in throttle body, then starts right up and will run and start all day long just fine except I have noticed at sea level, it boggs down when floored, but  drove it to denver and it runs perfect at higher elevations. any ideas??  Thank you

Answer
There are a couple of things to look at. First , is the check engine light lit ?
if so the first step is to find out what the codes are. Auto zone and Kragen etc.
will usually do this for free. Most of these guys are not mechanics and just having
the code will only tell you what road to go down.

That being said , fuel pressure on this vehicle should be approx. 60 to 66 psi ,
it wont start on its own with less.

There is a recall # 99066f regarding the fuel injectors , either sticking closed
or part way open. this could cause your problem. try cycling the key on and off
3 times (on position for about 4 seconds) before attempting to start. This will
attempt to gain full fuel pressure if it is bleeding off over night.

Could be that your new fuel pump is defective. again check fuel pressure.

The problem with running at sea level but runs fine at higher altitude sounds
like a possible map sensor problem. this could also cause a hard start. did
the vehicle start ok in denver ? In a nutshell the map sensor tells the ecm
what altitude the car is at and how much fuel to deliver , i have seen some in
the past that basically told the ecm that you were at 19000 ft. when you were
at sea level , this wont necessarily set a check engine light. the ecm has no
way of knowing that this is a false reading.

Hope this helps ,, let me know if you need further help or information.