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03 chevy avalanche 5.3L 1/2ton 4wd
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wrenchdawg
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Apr 23, 2013, 5:52 PM
Post #1 of 29
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03 chevy avalanche 5.3L 1/2ton 4wd
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Fuel pressure issue. This engine requires 55 to 62 psi to idle and run correctly. After installing a new fuel pump the pressure was only 45psi and only rose 5psi with pressure regulator disconnected. Next install was a new pressure regulator. still only 45psi. Thought was, bad pump or regulator. checked pressure at fuel filter connection and it was 80 plus psi. that was with key on engine off. But at test port only 45psi. OK bad regulator, right? Replaced it with a top of the line regulator and still only 45-50psi.
Truck will start and run but quickly stalls after revving breifly. So, quality pump and regulator installed. What else could cause this problem? It has an electronic throttle, (no cable). TPS? Bad knock sensor? PLEASE, NEED HELP!
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 6:00 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Check engine light on?
Did you replace the fuel filter?
Did you dead head the pump at the fuel filter and got 80 psi?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 23, 2013, 6:01 PM)
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wrenchdawg
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Apr 23, 2013, 6:03 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Hi No engine light, no pending codes. New fuel filter. Dead head pump? I disconnected the line going into the filter and checked my pressure there.
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 6:11 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Dead head mean you basically cap off the supply line with your gauge, so there is no where for the fuel pressure to bleed off too. It puts a lot of stress on the pump motor, but it tells you what kind of pressure the pump is capable of putting out.
If you T'd your gauge inline before the filter and had 80 psi, but have 45 psi at the rail, you should check to make sure you didn't get a defective fuel filter ( should be able to blow through it) or check the line going from the filter filter to the rail for an obstruction.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 23, 2013, 6:12 PM)
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wrenchdawg
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Apr 23, 2013, 6:15 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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OK I capped it with my gauge & got 80psi
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 6:19 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Does the pressure hold at the rail when the pump isn't running after it has been primed and the pressure stablized? That is called rest pressure. It shouldn't bleed down more than 5 psi in one minute.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 23, 2013, 6:21 PM)
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wrenchdawg
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Apr 23, 2013, 6:21 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Yes it holds pressure. No bleed down.
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 6:27 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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What is the 8th digit of the VIN?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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wrenchdawg
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Apr 23, 2013, 6:31 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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T
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Discretesignals
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Apr 23, 2013, 6:40 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Reading the fuel pressure testing procedure. Fuel pressure without the engine running and fuel pump turned on a couple of times you should have a pressure of around 55-62 psi. When you have the engine running and vacuum at the regulator the fuel pressure is going to be around 3-10 psi less than 55-62 psi. So engine running pressure of around 45-50 psi should be good.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 23, 2013, 6:43 PM)
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wrenchdawg
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Apr 23, 2013, 6:47 PM
Post #11 of 29
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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With engine off and pump cycled 2 or 3 times I cant get over 45psi. With engine running my needle bounces rapidly between 35 & 45. with regulator connected. with vacuum disconnected it never reaches 50.
I am going to disconnect the fuel line again and put air to the line from the rail back to the filter and see if I get any junk comming out
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 6:52 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Did you make sure that your pump has good power and ground?
Did you install the updated pump connector?
You should see close to charging system voltage or battery voltage at the pump connector and less than 0.30 volts from the pump ground at the connector to the battery negative with the pump running.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Hammer Time
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Apr 23, 2013, 6:56 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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I don't believe 45 to 50 is acceptable here. This thing should be reading close to 60 KOEO and closer to 55 with vacuum applied to it.
Are you sure your gauge is accurate?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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wrenchdawg
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Apr 23, 2013, 7:14 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Yes, gauge is accurate. No, I wasnt aware of an updated connector. Still, why would I have strong pressure from the pump and such a huge drop at the rail? Thats not a voltage problem.
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 7:17 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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I've read several posts in IATN that around 48 psi KOER was normal in those years.
They list two different OEM part number for the fuel pressure regulator depending on if it is manual or automatic. Don't know the difference except for the price of the automatic OEM is more.
You really should validate your gauge as HT pointed out. If you could find another truck to plug into for comparison.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 23, 2013, 7:20 PM)
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Hammer Time
Ultimate Carjunky
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Apr 23, 2013, 7:19 PM
Post #16 of 29
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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They are normal for VIN "Z", not "T"
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 7:32 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Well, 35 psi definitely isn't normal.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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wrenchdawg
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Apr 23, 2013, 7:39 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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My gauge is accurate. My gauge doesnt have anything to do with the truck stalling. That other regulator for manual trans is smaller in diameter and has the vacuum port on the side rather than the top. One will not fit the other.
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 7:44 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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How does it run when your driving it? Does it bog out at wide open throttle while driving?
Did you disconnect the battery at any time?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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wrenchdawg
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Apr 23, 2013, 7:51 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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It does ok driving down the road. But aproaching a stop is when it dies. The negative was disconnected while I did the pump.
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Discretesignals
Ultimate Carjunky
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Apr 23, 2013, 7:56 PM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Try cleaning the throttle bore and throttle blade with a rag and carb cleaner. When you disconnect the battery it will clear the throttle adaptation. The computer will try to learn throttle adaptation on a gummy throttle and it will cause stalling and/or low idle, especially when the a/c is running.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 23, 2013, 7:57 PM)
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wrenchdawg
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Apr 23, 2013, 8:11 PM
Post #23 of 29
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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Ok Going to blow out fuel line, clean throttle bore and plate and just because, Im going to get another regulator.
I will post the results when I have them.
Thanks
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Hammer Time
Ultimate Carjunky
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Apr 24, 2013, 3:22 AM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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There is nothing wrong with your fuel line. Putting air pressure to your fuel line is very risky to the EVAP system and I wouldn't do that.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
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Apr 24, 2013, 5:07 AM
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Re: 03 chevy avalanche 5.3L 1/2ton 4wd
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It probably isn't a fuel delivery issue if you only have stalling at idle speeds
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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