1996 Chevrolet Blazer Fuel pressure

1996 CHEVROLET BLAZER
189,900 MILES • 4.3L • V6 • 4WD • AUTOMATIC
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TOM1984
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Last week i went to start my car and i had a no start, checked schrader and had no fuel but i heard the pump turn on everytime. So i dropped tank and tested fuel pump with my jumper box and it shot gas out no prob. I put the tank back in the blazer and put in new filter, and it almost started for a few cranks then after about 7 tries it lost all pressure again. So i got a new pump dropped the tank again replaced the pump and put everything back primed the pump and started the blazer and it idled very well. I let it idle for a little bit then i got in and reved it up but it just bogged down. I tried playing with it for a little bit but kept trying to bog down then it died. I started it back up and it revved really hi then died and now its back to no pressure just cranking over . The pump always turns on and primes everytime. Wondering if maybe there is air in the line. Im so stumped any help would b appreciated
Jan 20, 2015 at 7:37 PM
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OBXAUTOMEDIC
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Hello,

The most likely culprit is what is known as the Spider Assembly or Fuel Injector Assembly it is located under the Plenum.

To Test you will need a fuel pressure tested.You will need to do a leak down test.

1) Connect the pressure tester. Place some rags or something to catch any gas that may spill

2) Have someone cycle the key to the on position Not Start/Run a few time to pressurize the system, check around the pressure tester to make sure of no leaks.

3) Pressurize the system again and Watch the gauge - one of 2 things will happen

1 - you will see a drop of 5 psi and then hold steady for at least 1 minute

2 - the gauge will drop to 0 psi

If the gauge drops to zero then most likely the Fuel Pressure Regulator is bad. And in order to verify you will have to remove the plenum.
Jan 20, 2015 at 8:29 PM
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TOM1984
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Ive heard of those going bad. My problem is before the schader vslve though. When i first put fuel filter and tank in it get fuel pressure but after just a few minutes it starts to loose pressure. Even with new pump it starts fine then starts to bog then barely starts then just cranking. Was thinking air got in the fuel system some how
Jan 20, 2015 at 8:47 PM
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OBXAUTOMEDIC
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OK, if you have checked and have no leaks between the schrader valve and the tank then what you are describing is possibly the Fuel Pressure Regulator or the Spider assembly.
Jan 20, 2015 at 9:25 PM
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TOM1984
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And those would cause zero fuel pressure at the schrader valve?
Jan 20, 2015 at 9:47 PM
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TOM1984
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I put on the pressure tester and im getting 0 psi and thats with a new fuel filter, and i can hear the pump turn on every time. When i push the schradder in i get alot of air coming out.
Jan 20, 2015 at 10:22 PM
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OBXAUTOMEDIC
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Yes, the fuel pressure regulator regulates the pressure and if it has failed then it is not doing it's job and a very low pressure or a zero pressure is a result.What happens is it is just redirecting all the gas back to the tank threw the return line.
Jan 21, 2015 at 4:52 AM
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TOM1984
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Ok well i believe you are correct, but is there a way i can test for leaks or something just to make sure? I was trying to sell this blazer and after one person test drove i took it home, and the next morning is when this happened. So i want to get it fixed asap but dont want to throw money where i dont need to since that will lessen my profit. At the same time i dont want to sell someone a lemon either
Jan 21, 2015 at 9:20 AM
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OBXAUTOMEDIC
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Well if you're not seeing any leaks from the Fuel Rail back to the tank then it is most likely leaking at the fuel pressure regulator. And the only way to check is to remove the intake manifold plenum. And so you know there is a strong possibility that if no corrected and you keep trying to start and run it that the fuel leaking into the top of the intake manifold can start a fire and then you'll be out even more $$$. The only thing to do is fix it and raise the price. Also better that it done it before then a day after you sold it.

It is not to difficult if your mechanically inclined but would recommend replacing the whole assembly and not just the pressure regulator.
Jan 21, 2015 at 5:01 PM
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TOM1984
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ok i replaced the fuel pressure regulator with a new one and hooked the lines up with the plenum off real quick and when i turn the key the psi jumps up to 60 or so then when the pump relay clicks off it drops down to 10 or so instantly. any ideas?
Feb 4, 2015 at 11:43 AM
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OBXAUTOMEDIC
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Sorry didn't get back sooner been little busy...

OK, well it shouldn't drop instantly but at least your are now getting pressure. So, you may also have an open injector. You could if still have intake off pull injector and pressurize the system and see if any are leaking.
Feb 5, 2015 at 12:23 PM
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TOM1984
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well i did notice just now that one of the little plastic tabs at the end of the injector is broke so thats the one leaking im sure i just ordered the whole assembly
Feb 5, 2015 at 4:18 PM
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OBXAUTOMEDIC
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Yes unfortunately that tends to happen when working around them especially if original, Sorry for the misfortune nut should be good to go once get the assembly replaced.
Feb 6, 2015 at 7:17 AM