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  1. #1

    Default 1997 gmc yukon 5.7 fuel pressure

    i have a 1997 gmc yukon that i purchased for my 17 year old son. figured be a great first truck for a new driver. been running great for 6 months till now .truck kept dying so i replaced battery .next day my wife drove it and died .started back up when i meet her to pick it up on way home i noticed my 17 year old didnt put gas in so was running low .as i proceeded up a hill the car would not exceed 30 mph and loud clanking noise coming from engine .proceeded to make it home put fuel in and it did get a little better .drove around and check engine light came on .bank 1 sensor 1 code and maf came up. all changed and still stalling every once and a while .oh and also changed fuel filter .today i changed iac valve running a little better .about an hour ago driving around will not exceed 30 mph but no clanking from engine .went to auto zone rented fuel pressure tester .numbers are as follows at prime 35
    at start up 50
    at 2500 rpms 52
    holds at 50 for 20 mins then drops to 46
    release air valve while running truck shuts off

    please advise what to do next if you can thanks

  2. #2

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    All of those numbers look low to me. If you cycle the key on and off a few times (to "prime" the pump more), does the pressure ever get near 60 psi? If you can find the "test lead" for the fuel pump (see a wiring diagram) so you can run the pump manually, can you run the pump so the pressure gets up near 60+ psi? If you carefully clamp off a rubber section of the return line, does the pressure increase? The highest pressure you list is 52 psi -- much lower than the spec of 60-66 that is usually given for these fuel systems. It suggests to me that something is wrong in the fuel system. At this point, bad pump seems most likely.
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  3. #3
    Jr. Engineer Jamm3r's Avatar
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    Dec 2012
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    Minneapolis area
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    Fuel pump problems are common with these; so are fuel pressure regulator problems. If the truck is holding pressure then the regulator is probably not the problem. Neither is easy to fix.

    If you want to be sure you can duct tape your fuel pressure gauge to the windshield so you can see it while driving.

    You will have to drop the tank to fix it, I think, unless maybe it's possible to cut a hole in the floor. Not that hard to drop the tank, be sure there's no fuel in it and then use a floor jack to support it.

    I replaced mine with a cheap fuel pump and had to do it again three years later. Don't make that mistake.
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  4. #4

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    Yeah I would say fuel pump.. And if you still have problems check the pressure on the new one.. I have gotten a bad fuel pump(and sending unit) before and paid big money at autozone for it. I bought the replacement pump only(no sending unit) off ebay for less than $100. It came with a one year warranty (better than the local auto parts stores which were only 90 days) That one lasted.... yup you guessed it.. 1 year and 3 weeks... I actually bought another from the same guy only because of the warranty. They were AC Delco pumps too.




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  5. #5

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    Quote Originally Posted by the phantom View Post
    Yeah I would say fuel pump.. And if you still have problems check the pressure on the new one.. I have gotten a bad fuel pump(and sending unit) before and paid big money at autozone for it. I bought the replacement pump only(no sending unit) off ebay for less than $100. It came with a one year warranty (better than the local auto parts stores which were only 90 days) That one lasted.... yup you guessed it.. 1 year and 3 weeks... I actually bought another from the same guy only because of the warranty. They were AC Delco pumps too.
    just picked up a fuel pump from napa debating to do it myself or pay somebody.cost me $193.00

    - - - Updated - - -

    got some young guys from napa that would do in my driveway .one kid wants 40 bucks an hour and the other wants 120 if he doesnt run into any problems .

  6. #6
    Jr. Engineer
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    You said you "almost" changed the fuel filter,,,well,, you "almost" might have had it fixed! That would have been the first thing I would have changed!

  7. #7

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    Quote Originally Posted by zuki82 View Post
    You said you "almost" changed the fuel filter,,,well,, you "almost" might have had it fixed! That would have been the first thing I would have changed!
    I didnt see "almost" in his post. It says "oh and also changed fuel filter"

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