fuel pump has been replaced with a brand new one i used the seal provided as the stock one became brittle as broke apart with it for the tank lock, fuel pressure was 34lbs while idleing rev it up goes to 42

gauge is accurate starts 44 lbs when the key is turned, 34 lbs while idling, and rises in conjunction with the throttle to about 42lbs at 3,000

Before modifiying anything We put a fuel pressure gauge onto the fuel rail, and it was running 42 lbs. of pressure while starting. While running it would drop down to about 34 lbs of pressure, and after shutting the car off the pressure would drop straight to zero. We replaced the fuel pressure regulator, and it would start and hold pressure fine, but when I would run it over 3,000 rpms it would start to bog out instead of giving more power

Replaced the fuel filter, and the following day it would still have the same symptoms, the fuel is getting starved from the low fuel pressure that the pump it pushing. Removed the fuel lines from the fuel sending unit and there was no pressure at all, so now im replacing the fuel pump and strainer which is done now its much harder putting all the lines back on than there was taking off always fun spent about 4-hours so far

Put the computer scanner back on today, no error codes, fuel pressure gauge is at 42 lbs while starting and while running has 34 lbs of pressure, still hesitates really bad at intersections, doesnt want to run at high speeds

so the fuel pressure was the same now as it was before I replaced the fuel pump

only borrowed the gauge so I dont have one at the moment to test once again

here the w-body threads

1
http://www.w-body.com/forum/index.php?topic=77060.0

2
http://www.w-body.com/forum/index.php?topic=81857.0

maybe this can help a lil

I reused the old fuel pump pulsator when replacing with the new pump maybe this is leaking and maybe my old pump really wasnt bad is it normal for the fuel pressure to be at 34 lbs, while idleing in park

From what the books tells me, it says. 41-47 psi for KOEO test line off.  It should hold that pressure for atleast 2 hours dropping no more than 1-3 psi per 2 hours.

I had just replaced the fuel pressure regulator , before KOEO 42 psi, KOEO 34 psi , turn key off all fuel pressure would instantly drop 0

now KOEO 42 psi, KOEO 34 psi, KOEO with a lil rev at would rise to 40-42 psi

On my TGP, the Pulsator in the tank got all gapped out and let all the pressure bleed off and make it run odd. Also, the pump SHOULD put out 40 psi when running or just key on engine off. I couldnt even get my TGPs fuel pressure below 42psi. Sounds like the wrong pump, its easy to put a normal pump in.

Almost positive the pulsator was bad to begin with not my fuel pump because pressure was the same right as soon as it startin runnin shitty before i replaced the pump, after that used the old pulsator, it must be leakin because the pressure regulator is brand new, no gas in the vacuum line, holds

The pump was one of these two cant remember what harness code mine is but i did put the correct coded one in because I removed the old pump first got the code from the harness plug bought the right one then replaced
Airtex Master / Fuel Pum
For your 1990 Pontiac Grand Prix 3.1L FI Turbo 6cyl

Part Number:     E3265
Weight:    0.8 lbs
Warranty:    1 YR
Notes:    With harness code "WAA" or "WEK" ***Caution*** A fuel pump is more likely to fail if installed without a new strainer and filter. Warranty valid only if strainer is replaced at the same time as the fuel pump. Drop fuel tank and clean before replacing fuel pump.
Fitting Size:    Outlet - 5/16 in.
Fitting Type:    Inlet - filter, outlet - hose connection
Gallons Per Hour:    40
Pressure Rating:    65-95 psi
Shipping Information:    Overnight and Two Day shipping are not available for PO Box, APO/FPO/DPO or US Territory addresses.

Part Number:     E3210
Weight:    0.9 lbs
Warranty:    1 YR
Notes:    With harness code "WEG" or "WES" ***Caution*** a fuel pump is more likely to fail if installed without a new strainer and filter. Warranty valid only if strainer is replaced at the same time as the fuel pump. Drop fuel tank and clean before replacing fuel pump.
Fitting Size:    Outlet - 5/16 in.
Fitting Type:    Inlet - filter, outlet - hose connection
Gallons Per Hour:    40
Pressure Rating:    65-95 psi
Shipping Information:    Overnight and Two Day shipping are not available for PO Box, APO/FPO/DPO or US Territory addresses.

when i put in my 255lph pump in i didnt use the pulsator.... can anyone confirm this pulsator does anything? If not you could just bypass it with FI grade hose. 

Quote from: PhatMpk on December 29, 2009, 04:29:47 PM
I had just replaced the fuel pressure regulator , before KOEO 42 psi, KOEO 34 psi , turn key off all fuel pressure would instantly drop 0

now KOEO 42 psi, KOEO 34 psi, KOEO with a lil rev at would rise to 40-42 psi

I told you in the other thread your KOEO pressure looked ok, but running pressure was low. Does it still drop quickly when you shut off the car or does it hold now? Pressure should hold for a while after shutting off the car. If it bleeds off quickly, you have something leaking down. Usually, you'll have a bit of a hard start with a leaking pulsator....but if the leak is very small, it might start normally but just have low pressure.

Here's a quote from me about fuel pressure drop acceptable rates:

QuoteThe general rule of thumb is that the pressure should not drop off more than 5psi in a 10 minute time period.

Quote from: killinprixs on December 29, 2009, 08:25:32 PM
when i put in my 255lph pump in i didnt use the pulsator.... can anyone confirm this pulsator does anything? If not you could just bypass it with FI grade hose.  

The pulsator is there to dampen vibrations/pulses from the pumping operation/action of the pump. It basically cancels out noise. If you used the supplied fuel grade hose instead of the pulsator, you might notice a bit more fuel pump noise. The little circular object on the fuel line just before the fuel rail supposed to serve the same purpose. A lot of people use the hose instead of the pulsator. AC Delco Pulsators used to be available from part stores(autozone) a few years ago if you do choose to run one.

yes thanks man i noticed it but didnt really think of it going to bypass it prolly this coming week, fuel pressure holds fine at 42-40 in the rail when key off doesnt bleed quickly

great info , thanks Matt!   

good luck man, at least you have those new injectors in there so when you finally fix the problem she should be running like new again.  Good to see another TGP owner with patience anyway.

Quote from: killinprixs on December 29, 2009, 11:05:10 PM
Good to see another TGP owner with patience anyway.

Patience is a virtue thats for sure!

I can't believe my car even ran when I put it back together! Ive been working bugs out since march and the cars still not 100%

Plug wires seem to go fast! :laugh: 3rd set now

ordered my OWN fuel pressure gauge kit, comes with fuel grade hose and clamps as well needed to bypass, need to get the jack stands back from my dads friend, he is out of town at the moment so prolly get to droppin the tank in the next couple weeks

friend threw out maybe the new fuel pressure regulator is out of spec, its looks like its a universal regulator Gp-Sorensen Fuel Injector Pressure Regulator Part # 800-218
fits these makes cant seem to find any other specs
what brand do you guys use to replace the regulator?

Make   Model   Year
BUICK    CENTURY SEDAN / COUPE    89-87
BUICK    REGAL SEDAN / COUPE    93-88
CADILLAC    CIMARRON    88-87
CHEVROLET    BERETTA    93-87
CHEVROLET    CAVALIER    94-87
CHEVROLET    CELEBRITY    90-87
CHEVROLET    CORSICA    93-87
CHEVROLET    LUMINA    94-90
OLDSMOBILE    CIERA / CUTLASS CIERA    89-87
OLDSMOBILE    CUTLASS / CUTLASS SUPREME    93-88
OLDSMOBILE    FIRENZA    87
PONTIAC    6000    91-87
PONTIAC    GRAND PRIX    93-88
PONTIAC    SUNBIRD    94-91
PONTIAC    TEMPEST    91-87

IIRC they are all the same.  I had replaced mine 4/5 years ago with a stock one with no issues.  make sure you replace the "o" rings.