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Cng leak out of prd valve

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  • Cng leak out of prd valve

    I have a 2000 cavalier I had my impco hpr 3600 just replaced. I started to smell natural gas coming from the hpr I got under the car with soap water and figured out it was the pressure relief device. So I called up s and l automotive and they said they could adjust it. 108 dollars later still leaking and not fixed. Go in again to s and l auto and they said they would fix it but it still leaks does anyone know what I should do or how to fix my problem please let me know thank you.

  • #2
    Re: Cng leak out of prd valve

    The pressure relief device on the HPR is there to protect the HPR. Most of the problems associated with this pressure relief device is that it will make popping sounds. This is the first time that I have heard of one leaking (I assume you are talking about a small continous leak). Replacing just the pressure relief device often times doesn't fix the problem. Most people end up replacing the entire HPR. You can search Ebay, KSL, etc. and find a used one somewhere.
    Jared.
    Mountain Green, Utah
    2003 CNG Cavalier
    2003 CNG Silverado 2500HD

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    • #3
      Re: Cng leak out of prd valve

      I agree with Highmarker. In addition you stated that the HPR was new; return it as defective. From what I have seen, that "mid pressure relief " is set at about 400 psi. Why did it activate? Was the relief valve was defective from the start or it was activated because main part of the pressure regulator failed to limit pressure to something below 150 psi and the relief is protecting the low pressure side of the system.
      Also, I do not believe these relief valves are NOT adjustable. Does this shop have the equipment to properly check and adjust the relief valve (it is not rocket science) My best guess is that it activated and got some dirt under the valve. If it is anything like the GFI "mid pressrue relief" I've disected, it is a flat rubber valve with a half round seat which will leak and do. Yes Impco has a much petter record of relief valve service.
      Although chances are slim, you might ask for t he $108 back, and try another shop

      NFPA 52 states that PRD' s are not to be adjustable on automotive systems, and are to be a one time use item. (paraphrased). If you consider this a PRD (which I don't be cause of the its construction) it should not be adjusted

      Larrycng

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      • #4
        Re: Cng leak out of prd valve

        I don't hear a popping sound it just leaks slowly thats all. If anyone knows how to fix this please let me know I dont have the money to go and buy another hpr and have it installed its expensive. thanks

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        • #5
          Re: Cng leak out of prd valve

          I don't know the price but the part number for the HPR-3600's "pressure relief valve" is V1-14137. This is from the August 2008 Impco Master Parts Catalog. page 213.

          Good luck

          Larrycng
          Last edited by larrycng; 05-19-2010, 09:17 PM.

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          • #6
            Re: Cng leak out of prd valve

            I don't know the price, but the part number for the HPR-3600's "pressure reliev valve" is V1-14137. This is from the August 2008 Master Parts Catalog page 213.

            Good luck

            Larrycng

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            • #7
              Re: Cng leak out of prd valve

              I had a problem with my HPR a couple of years ago, and I found it leaking from the pressure relief valve as well. I removed the pressure relief valve from the regulator, Googled the part number and came up with an alternate - Sherwood PV3865 rated at 400 psig. I bought some on E-Bay (package of 3), but it didn't work. Turned out that my HPR was bad and the relief valve was just doing it's job. You're welcome to take one of these relief valves that I have and try it, but I'd place a bet you have a faulty regulator.
              2000 Cavalier

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              • #8
                Re: Cng leak out of prd valve

                If the PRD is indeed leaking, it means that 400 psig plus is in the second stage of the regulator, which should be around 125 psig, and that means that you are getting 400 psig plus into your injectors and related fuel lines. I would be surprised to see the vehicle even run.
                Also, if the PRD is activating, it usually pops, not seeping. It is possible the threads are not machined fully and it is leaking there, or a possible defect in the HPR itself. I agree with Larry, diagnosing this is not rocket sciehce, and the PRD are NOT adjustable and cannot be according to code. Anyone who adjusts them are violating code and could be subject to penalties, depending on where they are.

                Franz

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