04 won't turn over

Okay, the other day walked out to my Suburban, got in drove up town and back turned it off and got out. Went to get back in later to go back up town and it would not start. It would turn over, you could hear the fuel pump kicking on, but wouldn't start. FP was 37 i believe. Hit the fuel tank etc. later it started up. Didn't go anywhere, cut if off. Went to move it the next day to cut the grass and you could hear the fuel pump kick on, but would not turn over. Did not hear anything. Kept trying and nothing. Messed with some fuses, etc it started and I moved it. I went to get in it to take it to the shop to get the fuel pump replaced and still nothing. You hear the fuel pump kick on once you turn the ignition, the dash lights light up, but the motor will not start. No sound at all. Does anyone know what this could be?:confused:

You need to isolate whether the issue is fuel or ignition. Spray some starting fluid into the air cleaner or throat, see if it runs for a few seconds. If not, check for spark.

So what was the cause for the vehicle not starting.

Fuel pressure is WAY WAY too low.

Do a complete fuel pressure test.

This is a quote from MT-2500:

You need more fuel pressure for injectors to squirt on a cold start.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.