Engine Cranks too much prior to starting

[drummerdude]

I have a 2002 Tahoe 4x4. I was having some problems starting it. It has been cranking too long prior to starting. My check engine light was on and the codes read P0171 and P0174. These related to the 02 sensors, so I went ahead and replaced them all. I also have cleaned the MAF and the Throttle Body. I also put new plugs and wires in it.
Had the codes cleared and the check engine light is on again. Not sure what the code is just yet as I have not had time to check it.
However I do notice a low pitched humming near the gas tank. Is my fuel pump going bad?
Any help is appreciated. Thanks

 

[Donut Slayer]

Sounds like it. Try this, turn the key to the run position but don't start it, wait til you hear the pump turn off then try to crank it. If it starts right up, your pump is loosing its prime.

 

[drummerdude]

Thanks dude. I will try this. I do notice that my fuel pump does sound differently that it normally does. It used to be kind of high pitched and now it seems to be a low hum. Does the fuel tank need to be dropped to replace it?
Thanks

 

[Donut Slayer]

yep, tank has to be dropped. But before you do, get a fuel pressure gauge and test it on the schrader valve on the engine to confirm low pressure. BTW, have you changed the fuel filter lately? its located on the frame rail under the driver. That would save a headache if that was the cause.

 

[drummerdude]

Yes, the fuel filter was changed about 3 months ago. Taking to a mechanic today, so we'll see how it goes.
Thanks for all your help.