04 5.3 fuel pressure issue

[skaffy03]

I have a 2004 Tahoe 5.3 Flex Fuel (L59) @ 172k miles
212/218 Comp Cam
CAI
LTs
BB Tune

Anyways... girlfriend calls me a few days ago, says truck will crank but not start. I had a friend go check it out while i was working and he got it to run. It had 1/8 of a tank, facing downhill, and had not been started for 2 days. It's been fine since...

but.. i used a fuel pressure tester anyways.. flex fuel engines run at lower pressure around 45-54psi with regulator line disconnected.

With the key ON, engine OFF, my pressure does not build unless I cycle the key on and off and even then it only builds about 5-10psi at a time, but does not drop rapidly. Weird...
With the engine ON and idling, my pressure holds steady around 45psi and dips to 40psi with more throttle. Regulator is dry and does not have an overwhelming smell of fuel and the pressure increases to about 52psi with the vacuum line OFF the regulator. Getting odd...

So, to sum it up... when I turn the key and crank the engine, it starts up the first time (most of the time) but takes a second longer. If I have to try cranking again, it "chugs" to life. If I just turn the key to ON and engine OFF, the pump will not make sufficient pressure. I do have intermittent 'surging' if I let the truck idle forward at a stop light and a hesitation when giving enough throttle to downshift and accelerate.

I'm thinking pump is on the way out, and soon. Can anyone back up my assumptions before I throw dollar bills at my "Hoe"?


This doesn't happen all the time and the truck drives fine most the time but just feels doggy some days. It's still driveable so I don't know if I should replace what's not broken.


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[electro]

I might suggest buy one and have it ready. With a good warranty and return policy.


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[dmperfection]

Did you get this figured out? I would have suggested fuel filter first, but pumps are notorious for going out. Mine has gone out twice, but I've got 230k miles on my '02 Tahoe. The pump sits right smack in the center of the tank. You can smack the center of the bottom of the tank with your hand or rubber mallet to see if the pump reacts for better or worse to get you closer to determining if the pump is bad or not.

 

[skaffy03]

Sorry, I have not been able to figure out the problem yet.

When I was on my way to my buddies house to do it, my tahoe starting making a whining and howling noise like the rear end is going out. So I figured I'd get that taken care of first before it grenades at 70mph. But I do believe it is the pump


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