Chevrolet Repair: 1998 7.4 l hard to start warm, coolant temp, descretion

Question
I have a 1998 gmc 2500 4x4 with a 7.4 l engine. Starts better the colder it is-have to crank a long time if the engine is warm.Fuel pressure is fine -coolant temp sensors fine Any suggestions? It is very frustrating-otherwise truck runs fine-also doesn't matter if you cycle the key or hold the pedal to the floor.Thank-you.

Answer
Hi Daniel,

You have a very large truck.  Sounds nice.  My idea is to check the O2 sensor.  Have you noticed a drop in fuel economy?  Do you have a check engine light?  I am guessing NO or you would have stated that.  

Once you are warmed up, you are in closed loop.  In that mode, you are mostly at the descretion of the O2 sensor, concerning fuel delivery.  All the other sensors react the same way, hot or cold.  If the O2 is telling the computer that the fuel is too rich, it will lean the mixture at cranking.  It will also work in reverse, but you are not complaining about gas smell.  Typically when an O2 gets gunked up, it will register too rich.  May not always throw a code.  

You want to go to a store who will check your computer for you, for free.  I live in Michigan, and here we have Autozone.  If you go there, they will check your computer for you for free, and then sell you the part you need.  You may have a place similar by you.  The O2 needs to cycle up and down constantly.  If it does not and stays high, your computer is being told to lean the mixture.  

Hope this helps.

C J S