Help Me Diagnose This Fuel Problem

[glueguy]

2001 Suburban LS1500 5.3 Vortec, 133k. Long but I want to give all the info I've got.

 

Started it yesterday, no throttle response in the driveway, ran terrible down the street. Backed up to punt and take another vehicle, magically cleared up. Drove it 5 miles no problem. At a light died and wouldn't restart. Finally caught and with lots of throttle input stayed running and cleared up again enough to get home. Set codes P0171 P0174.

 

This morning cleaned the MAF. Reassembled, started and run perfectly smooth. Idled 3-5 minutes then died on its own and wouldn't restart. Took off the air duct from the MAF to the throttle body, sprayed starter fluid, would start and run a few seconds and then die.

 

Tried to coax it from the street into the garage, thinking fuel pump. Air duct off, spray starter fluid, would be able to move it 6 inches before it would die. Then I disconnected the MAF (realizing that without the air tube there was no connection between the MAF and the engine). As soon as I disconnected the MAF it started, idled smooth and made it all the way up the drive.

 

Went to pick up a fuel pump and got to thinking. Came back, started with the MAF disconnected. Started right up, idled for a few minutes. The second I touched the accelerator pedal (after perfect dead smooth idle for minutes) it coughed and died and wouldn't refire. Got it to restart but it ran low rpm for 5 seconds and died.

 

With the air duct off, turn the key on and there is a click from underneath at approx two seconds, and a buzz under the hood for about 10-15 seconds. This one sounds like the fuel system pressurizing. When this happens, the throttle body cracks open, and then when the buzz stops it shuts again.

 

I put a test light on the fuel pump relay in the underhood fuse box and it lights for two seconds. There is a click near the back of the intake when the light goes out. I can't convince myself that I hear the pump running, but there is that definite high pitch whine related to the throttle body cracking that sounds so much like fuel pressurizing the system. Hate that I don't have a pressure gauge with me.

 

I'm not excited about changing the fuel pump if that's not the problem. Any ideas? I can buy a replacement MAF tomorrow but I hate just throwing parts and hoping for the best, although I would _much_ rather change the MAF rather than the fuel pump.

 

Appreciate anything you've got for me.