Cannot start after warm up

[daisyrocky]

:scratch::scratch:Hi everyone, my 97 Ex 4.0 will start up fine in the morning but after parked for 45 min or so and it needs to crank at least 2-3 times before turning over. This never missed. I've replaced the upper lower intake gaskets, iac valve, clean the maf sensor and it's still doing it. After 3 or 4 hours it start right up the first crank but not after 30 minutes -1 hour, I need to step on gas pedal to help get it started. What can it be???:scratch:

 

[Flag Gibby]

I am thinking that it might be your oxygen sensor.

 

[2000StreetRod]

ECT sensor?

A rich mixture will impede a warm start. Are there any DTCs? Maybe the engine coolant temperature (ECT) sensor is defective.

 

[daisyrocky]

Thanks everyone. No codes and just replaced with the updated thermostat housing and the two motorcraft sensors with the clip on kind. Won't the oxygen sensors throw any codes if they bad?

 

[daisyrocky]

Cut fuel pump access door, replaced fuel pump. No more starting problem!