Loud whine, brand new fuel pump.

[jmc1997ck]

Mine sounds like an airliner on the tarmac, too (as did the original). Seems to be a signature sound of these Chevy's. Much akin to Ford power steering pumps...

 

[hefftone]

Lol, yeah fellas, it is TBI which specs 9-13psi. Initially it whines but quietly, sounds like any other fuel pump. But now after it runs for a few minutes is sounds like a freaking "power juicer" machine. I'll have to record it tomorrow morning. The pump was recommended by Brian @ TBi chips. I've been wondering if its a voltage/current thing. Not sure what kind of amps these pumps pull.

 

[hefftone]

More weird crap today. The pump was not noisy today, but it would only drive using the first 25% of throttle. Giving it more than that, there was just no power. It stalled out while I was driving about 45mph. I pulled off the road. Waited about 1 minute. It restarted fine and drove a little better. But on the way back home it still only made power with the first 1/4 of throttle. I'm baffled? Got a cell, but it went away when I turned it off.
**Pulled the codes. Got a 44 lean exhaust (again) and a 24 (vss). Speedometer did County out earlier. Now there is a rattling buzz coming from the IAC. Goes away on disconnect.
http://www.youtube.com/watch?feature=youtube_gdata_player&v=MxiELpTxebg
I took it out for another spin. Runs awesome and then it will just fall on its face. Feels like running out of gas.
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[jmc1997ck]

Issues like this make me miss my '70 Ranchero. Wish I had more insight, my friend. Keep posting as you find issues and resolutions...

 

[NacIK]

Mine has done it ever since I changed it out for the new ACDelco. Scared the crap out of me because my old one used to do it to me when it was extremely low on gas and right before it died.

It is common now for the new ones. I was told by Delco it is because the pump is mounted lower on the new design.

 

[hefftone]

It had even less gas in it before, and ran perfectly fine. I added more gas to raise the level....besides all that, I am running the new pump on the old style sender, so the pump is in the stock location.
Everything in the fuel system is new, pump, filter, tbi rebuild, new FPR spring, even The o2 sensor is a new bosch. With the air cleaner assembly removed and giving some throttle, their is no delay to the big blast of fuel.
But on the road, the problem worsens, its almost intermittent. It sits and idles just fine, it rolls out and cruises with extremely light throttle. But more than that and it feels like fuel starvation. Sometimes when I step on it, it hauls ass....but usually it falls on its face....feels like when you run out of gas.
I am thinking along the lines of fuel related sensor (map/O2) or somethinng in the ignition....but as far as my experience with ignition problems, when they go (coil, ICM) they are totally done.
Any ideas out there on the troubleshooting? I'm runnning out of ideas.

 

[sewlow]

Just an idea, but is there any vacuum leakage. These trucks are getting pretty old. Maybe there is a crack in one of the lines. Sounds like your getting a lean-out condition. A guess.

 

[hefftone]

*.*.*.*.*UPDATE*.*.*.*.*
I borrowed a fuel pressure test kit from the auolto parts store today. I hooked it up on the outlet of the fuel filter (2 months old). Fuel pressure is definitely the problem.
At idle, the gauge stays steady at 11psi (TBI). Blipping the throttle and it will dip down a couple of psi. So I pulled the gauge into the cab. And went on a short test drive. The truck will idle around and function with about 10% throttle, but if I bury it, the fuel pressure will fall all the way down to zero or about that in a matter of seconds.
Way I see it there is one of two things:
1.) The fuel filter is clogged and restricting flow.
2.) The fuel pump is bad.
I highly doubt #1, because when I replaced the pump, I used a shop-vac and sucked up every last bit of sediment I could get to. Regardless, I figure I will replace the fuel filter before I dive into replacement ring the #$%*ing fuel pump again!!!!
I'm thinking #2 could be the problem because of that sound it made. I wonder if the sock strainer fell off and it FOD'd itself out. The pump sounds fine now, but I figure whatever went through it trashed the internals and it can only push so much fuel.
Anybody heard of a pump strainer falling off?
Fuel pump in AC DElCO EP381 (97 Vortec)


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[hefftone]

Pull bed back and removed fuel pump. No obvious signs of trouble. Is there a way to have this pump pressure tested?
I hope I didn't pull it out for nothing.

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[hefftone]

Reinstalled pump to test. The pressure gauge was ill fitting to my schrader valve and was a little inconsistent. Squeezing the return line the pump would easily push up to 40psi. I revved the engine and could not duplicate the previous symptoms. I cleaned up some chassis grounds after measuring some voltage drop in the ground side (see you tube for voltage drop testing). I did not test the + side.

Well after all that inconclusive crap, I slapped the bed back on and took it for a spin. It did not display the same poor performance characteristics. Its definitely driving better. No stalls or heavy bogging. Did not feel quite as peppy as before at full throttle.
We'll see how it works after some more test drives. Will check +side for voltage drop. Will replace fuel filter as the fuel looks horrendous (bleed tube from pressure gauge, gas looked like tea).

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