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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"?
 
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