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Thread: Fuel Pressure drop @ WOT?
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08-10-2008, 09:00 PM #1
Fuel Pressure drop @ WOT?
I'm diagnosing a lean condition at WOT. Pretty much have it something in the fuel delivery.
I checked the fuel pressure, 58 steady, and then dips to 54-55 when I hit WOT. Pops right back to 58 when I let off the pedal. I assume that is a normal drop, right?
So if pressure is good, does it mean the pump is perfectly fine? Or is there some other way to check?
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08-10-2008, 09:02 PM #2
- Join Date
- Aug 2005
- Location
- Thornton, CO
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- 23,773
Red Tint Jewelcoat- 2008 Trailblazer SS
Completely normal.
Flow = loss of pressure.2008 Trailblazer SS
Yank PTB3600, Kooks 1 7/8" LT's, 4" intake, E-fans, Magnaflow, Sonnax kit, tranny cooler, tune.
Lowered, HID's, tinted.
1999 Pontiac Trans Am WS.6 #1747 SOLD
531.1 RWHP 481.3 FT/Pounds all motor.
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08-11-2008, 06:34 AM #3
So if that pressure is normal, should I assume my pump/regulator is good and look elsewhere?
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08-11-2008, 06:42 AM #4
- Join Date
- Aug 2005
- Location
- Thornton, CO
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Red Tint Jewelcoat- 2008 Trailblazer SS
What mods?
If you are at 54PSI with WOT...that is normal. Maybe just a touch low, but you are safe over 52-53.
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08-11-2008, 01:37 PM #5
My mods
228R cam, pulleys, LT headers, LS6 intake, GMAF, lid, SY3500 converter w/ shift kit, 3.90 gears, cutout, borla...
I've eliminated the GMAF (problem remains even in SD mode) and I think the fuel pump/regulator is fine do to that pressure test.
Even when we forced the air/fuel ratio to 10.1 through EFILive, it still logged data at 14.7/1 at heavy throttle.
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08-11-2008, 07:18 PM #6
- Join Date
- Aug 2005
- Location
- Thornton, CO
- Posts
- 23,773
Red Tint Jewelcoat- 2008 Trailblazer SS
What tuning changes did you make when you ran SD?
Got a stuck injector?
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08-12-2008, 02:47 AM #7
Mr. Luos that is what i was thinking. maybe its stuck, but that would most likely set a P030X code. how lean are you at WOT
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08-12-2008, 02:50 AM #8
I don't have the full extend of all the details, and I'm away from my car until the weekend. Wouldn't a stuck injector be an easy find and wouldn't I feel it in performance?
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08-23-2008, 08:11 AM #9
Lean problem found!
I finally found my lean problem at heavy throttle.
I had an A/F gauge as a place holder tapped into the wires just before the PCM. When I removed that, I still had the lean condition, but when I went to SD (disconnected MAF) I now showed a little rich at WOT. So I got a new stock MAF and left the A/F gauge out... and all is good. A little rich at WOT, but my tuner will tweak that.
That stupid A/F gauge was masking the ture problem because before when I drove in SD with the gauge still wired in, I still was lean.
Feels so good to have it fixed!
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08-23-2008, 04:40 PM #10
are you running a K&N filter by any chance?
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08-23-2008, 05:51 PM #11
K&N has been in for 50k miles or so. But the new MAF fixed my issue. I had a GMAF, instead of the stocker. Living proof that staying with the stock MAF is a wise choice.
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08-24-2008, 05:23 AM #12
fo sho. my slp maf was messing up a few weeks ago so i swapped my stocker in and runs great now. kn is excellent at getting oil on your maf wires and f'n it all up. glad to hear its running good now
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