Fuel Pressure Regulator - Problem after Intake Manifold work

Discussion in 'General Chevy & GM Tech Questions' started by thisiscrazy, Feb 27, 2013.

  1. thisiscrazy

    thisiscrazy New Member

    '99 Suburban 1500 V8, 5.7L 2WD

    Dealer replaced Intake Valve. "Service Engine" light on 8 miles later. Back to dealer. Saying need to replace Fuel Regulator, holding 50 lbs pressure but should hold 55 lbs.

    Thing is, the regulator is new, has maybe 500 miles on it. (Work done by my mechanic other than the dealer). And dealer said there is a problem with the intake gasket. They were wanting to charge me for both parts, but thanks to my warranty, we learned that the gasket was part of the work that they supposedly did during the first visit. Dealer caught in a LIE (shocking!).

    Question: Is it possible that the dealer damaged the regulator when doing the intake work? Or that the faulty gasket damaged the regulator? (Apologize if this is a dumb question!)

    Thanks for any feedback...

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  3. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    I'm sure it is possible that the regulator was damaged during the intake work. Determining yes or no with reasonable certainty will be difficult. I doubt the gasket itself would have any impact on the operation of the regulator.

    Is there more to the diagnosis other than the fuel system hold too low of pressure? If that's all there is to go on, I would suggest that the fuel pumps seem more prone to problems (be unable to generate enough pressure) than fuel pressure regulators are prone to not hold sufficient pressure. Did they do enough diagnosis to determine that the fuel pump is working correctly?
  4. thisiscrazy

    thisiscrazy New Member

    Thanks, that sounds reasonable. Is there a way to test each part independently? The service agent I'm working with said they "ran diagnostics" that shows pressure at the regulator, pump, injectors, etc. Based on their work so far, I don't believe anything they say. They're using the old "not an OEM part" excuse (referring to the regulator). Very frustrating.
  5. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    Testing the different parts of the fuel system is mostly accomplished with a fuel pressure gauge. The fuel system is a fairly simple continuously circulating system. The fuel pump is designed to be able to send more fuel at higher pressure than needed by the engine. The fuel pressure regulator is a basic back pressure regulator that allows the pressure to build to its set point (~60 psi), then opens to allow the excess back to the tank. A typical fuel pressure test starts by hooking up the fuel pressure gauge, run the pump and see what pressure is generated (I like to use the test lead to run the pump continuously). If the pressure does not come up to 60 psi like it should, then the question is whether the pump is generating enough pressure or if the regulator is opening too soon. This can be tested by finding a suitable "clamp" and clamping off a "soft" spot in the fuel return line. If this causes the pressure to jump above 60, then the regulator is opening too soon. If the pressure stays low, then the pump is not generating enough pressure.
  6. thisiscrazy

    thisiscrazy New Member

    Thank you for that explanation, Mr. Shorty. The better I understand the system, the better I can detect malarky. End of day call from agent, saying "the mechanic working on your vehicle was out today." Yeh, right. I think they're going to voluntarily eat the work b/c of the gasket lie. Not sure what truly caused delay. Straight answers tomorrow hopefully. Again, thank you for taking your time to post here.

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