Hard start, no start, erratic idle, random stall.

[tinfoil_hat]

Hello folks,
My truck was having some intermittent issues, now it won't start. When all this began a few months ago I hooked up a fuel pressure tester and got 62psi, no leak-down after 5 mins. Then a few weeks ago it was 60psi. Today she wouldn't start. The gauge read 52psi, no leak-down after a full minute. Does this seem like a clear fuel pump failure, or do I need to dig deeper?

Here is the full breakdown of what has been going on:
--This truck has always started instantly. About a year ago, it would randomly take about 3 seconds and then do a weak start, then even out. After a while this became a case of instant start up in the morning, then after work (in all temperatures) I would have to hold the throttle halfway down to fire up. This was pretty consistent behavior whether the truck was warm or cold but always instant start in the morning.
--The truck started to run rough with a #5 misfire which turned out to be a cracked spark plug. Plugs, wires, cap, rotor have maybe 15k miles, all Delco parts. New plug fixed the misfire but not the start issue.
--Truck has a lower intake leak near the firewall on the passenger side. It seems "stable" so I have been ignoring it for now.
--Compression test was good and pretty consistent (I forgot the numbers).
--Last few days the truck has done an odd thing where it would idle normally at 650rpm, then randomly idle at 1400rpm in gear or in park.
--Truck died when pulling away from a stop sign day before yesterday. Idiot light said "CHECK GAUGES". Temp normal, 1/4 tank of fuel, 14V. Fired up again, died when moved to Drive. Full throttle start, truck ran, idled high for a few miles. Did not die again despite several more stop signs. No codes thrown.
--Today, strong crank but no start.
--Battery is maybe 3 months old and strong. Clean, tight terminals.
--215k, hoping to drive it to 250k. I average 10k a year

My plan was to replace pump, filter, and maybe pressure module on spider. MPFI spider upgrade is on my to-do list but maybe outside the budget today.
Am I barking up the wrong tree here or throwing parts at it prematurely?
What is the p/n's for the correct Delphi or Delco pumps?
Better to replace the entire pump/hanger/harness ass'y, or just the pump motor?

Thanks for any help you can offer.

 

[stutaeng]

So you have a 5.0/5.7 Vortec? I would fix the intake manifold gasket first before doing anything else. Vacuum leaks cause all sorts of surging and stalling problems.

Do you have any codes? Sometimes codes are stored even though the SES light on the dash is not illuminated.

Also, 52 psi is below spec, so that needs to be addressed.

An yes, MPFI upgrade is a great time to do it when you do the intake manifold gaskets.

 

[Awest623]

So you have a 5.0/5.7 Vortec? I would fix the intake manifold gasket first before doing anything else. Vacuum leaks cause all sorts of surging and stalling problems.

Do you have any codes? Sometimes codes are stored even though the SES light on the dash is not illuminated.

Also, 52 psi is below spec, so that needs to be addressed.

An yes, MPFI upgrade is a great time to do it when you do the intake manifold gaskets.

And while you're at it you'll have the chance to inspect the distributor for a worn gear, etc.

 

[tinfoil_hat]

Here is an update:
I replaced the fuel pump and the truck now starts instantly every time. The engine feels smoother and I have more power. I will occasionally get an uneven idle at a stoplight which could very well be that vacuum leak. I also replaced the fuel filter.
As for my fuel pressure, it still reads low on my gauge. This could just be an inaccurate gauge but I am wondering if it's the fuel pressure regulator allowing fuel to bypass to the tank. I was going to do the spider in any event but I see the price of the Delco unit has gone up almost $100 since the last time I checked.