00' Denali Fuel Problems

VoCS · October 27, 2007

Hello,

I am assuming my fuel pump is bad and I want to check any other options before dropping the tank. Here is what preceeded my problems and what I have done:

-Fuel guage stopped working properly, shows full drops to no reading etc (normal running)

-Ran the truck very low on gas (very near out, if not completely) after years of never getting below 1/4

-2 days after running very low on gas truck sputtered on the freeway and would attempt to die with any acceleration, pulled over turned the truck off then on and it started and ran fine after some high rpm revs

-next week, intermittently (usually while cold) would hesitate/sputter on ~+1/3 pedal acceleration

-next week, worsening hesitation to today where anymore than 1/8th pedal would hesitate

Diagnosing today:

-"eye checked" fuel pressure by hitting the valve by the intake manifold while running spurted a little gas (not very high presure)

-decided to replace the fuel filer again even though normal service it was replaced ~30-40k ago (quick lube shop though so who knows)

-after replacing the fuel file and priming the pump a couple times the engine started fine but still had the same hesitation for a few minutes then died and showed little or no pressure at the valve described earlier

-Seemingly no pressure and engine won't start as if the new filter made things worse.

Notable point:

-the truck always had a "whine" while the ignition was on and I noticed today there is no more whine or anything really.

So my question is is there anything left I should check/replace that is cheap before dropping the tank or is what I have described the perfect death of a fuel pump in a 110K mile yukon?

Import Hater · October 27, 2007

I'd say you're on the right track. Little fuel pressure and the erratic fuel gauge readings would be all I'd need to see to diagnose the fuel pump module as being bad. Unfortunately, they're not cheap since they don't come as just a pump. You get a complete assembly with a pump, sender, float, and the pumbing. Be careful with the hard formed plastic EVAP lines when dropping the tank. More specifically, the little plastic retaining clips that latch the ends onto the fittings. They're not cheap to replace since they can't be bought seperately of buying the entire line it's on.

VoCS · October 28, 2007

Thanks for the advice. I replaced the fuel pump today and after two "primes" all my worries went away.

I got the fuel pump and decided that a "top down" approach would be the best since there are wire harness issues and repeat pump replacement for a self repairer could become costly in time and money. (mostly that I had a full tank of gas)

Trip report:

I have a "side tank" and underneath the drivers side back seat there is a hump where the fuel pump is located.

After removing the seat, trim, and carpet (in my model the sections of carpet meet around the point of access) I opened a large (but shallow) hole with a drill as close to the middle as possible to inspect and back out if needed.

I then used metal sheers to cut open an access area taking note (by diagram) of where the fuel lines and wiring are (all ran towards the drivers side).

Replaced the pump (two people needed or the gm tool to get the securing ring into place). A special tool (for weekend mechanics) is also required to remove the intake and return lines(is there a name for this?).

I covered the hole I made with a dual hinged plate with thick weather stripping and epoxy lining with a single screw "latch".

Things I would have done different:

Go OEM. The new pump is making "whining" noise already

Replace the fuel filter more often than recommended around 30-40k (you can't blow through *any* fuel filter taken off, there are liquids in there!)

NEVER EVER let my GM truck go empty or even close

Stay top heavy, keep the tank at or above half.