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2002 Chevy Express 3500 CNG fill up ????????

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  • 2002 Chevy Express 3500 CNG fill up ????????

    Ok....we finally got a couple CNG fill stations in our area..and although I've owned this van now for a little over a year..this past Sunday was my first EVER CNG fill on the van. I admit I was a little scared and didn't know what to expect. The sound of the gas entering the tanks made me jump a bit at first..but I got used to it.

    Anyway, the pump ran and filled my vehicle with just UNDER 9 gallons equivelant..and my bill was under $15.00......is this REALLY all my van holds for CNG? THere are two tanks under the rear end. Anyway....the fuel gauge in the van registered FULL, so I assume that was a FILL UP.....We drove around running errands all day sunday and we just ecstatic to be running on CNG..and no more RIP OFF unleaded. I drove from my home to work (14 miles) and notice the gauge slowly dropping from about the 3/4 mark down to just under 1/4 tank by the time I reached the parking lot. I could also smell just a "hint" of NG as I was driving.

    When I got to my parking spot, I opened my van door first, and then shut the van off, and I heard a loud "PPPPSSSSSS" for bout 2-3 seconds..just behind the driver side and under the van. Can I assume a leak somewhere? or is this a pressur relief..or normal operation??

    I have no owners manual or any info on the CNG system.....and like I said this was my first time using the CNG system..and it seemed to be working great.

    Any help, tips, or insite would be most welcome at this time.
    Thanks

    Dan H

  • #2
    Re: 2002 Chevy Express 3500 CNG fill up ????????

    Yep, that's about all the Bi-fuel van holds. Completely empty, and a good slow fill, it will hold about 9.5 GGE. You should get around 100 miles on a tank in city driving and possibly up to 120 miles in steady highway driving on a fast fill. The noise you heard might have been the relief valve on the high pressure regulator. The regulator (which is mounted on the frame rail near the rear of the drivers door has a PRD (pressure relief device) mounted on it to prevent high pressure NG from bypassing the regulator and getting into the intermediate pressure system. This is usually caused by the regulator sticking either by mechcanical failure in the regulator, or by the regulator freezing. It is getting cold enough right now to start seeing freezing at the regulator. Next time you run on CNG, listen for any noise from the regulator. The PRD usually "pops" when it goes off, not a PPPSSSSSS. The sound you are hearing may be a leak in the system in the area of the regulator. When you shut off the vehicle, the main gas valve (HPL) shuts off and then any excess stays at pressure. A fairly large leak would bleed off in a few seconds. Two things to check with the van running. First, find and check the high pressure regulator. With the vehicle warmed up, the regulator top cover (where the single line from the back of the van enters) should be warm to the touch along with the rubber hoses going to it. Next, with a spray bottle filled with soapy water, spray the regulator, lines and fittings in the area you heard the PPPPSSSSS and look for bubbles to see if anything is leaking. This includes the PRD on the regulator. You should not smell any "hint" of NG while driving.

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    • #3
      Re: 2002 Chevy Express 3500 CNG fill up ????????

      Hope you find that leak .... and quick.

      Remember to park that vehicle out of the garage! Also, keep away from any ignition source like open flame while leak continues.

      Let us know how this ends up getting resolved.

      P.S. Curious which Wisconsin city now has CNG for you? I've read that Kwik Trip is active in building public cng pumps at their petrol convenience stores.

      Comment


      • #4
        Re: 2002 Chevy Express 3500 CNG fill up ????????

        Thanks guys...I'll check those items...you have already helped me TONS!!

        KSneedsCNG - I am in LaCrosse, WI. We have two stations now with a 3rd on it's way, all 3 of them being at local Kwik Trip stations. We also travel up to Wausau WI to visit family...and they just got a CNG pump at the gas station located on exit 188...I can't remember the name of the station, but I know they just put in a CNG fill station.

        Dan

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        • #5
          Re: 2002 Chevy Express 3500 CNG fill up ????????

          Originally posted by siai47 View Post
          Yep, that's about all the Bi-fuel van holds. Completely empty, and a good slow fill, it will hold about 9.5 GGE. You should get around 100 miles on a tank in city driving and possibly up to 120 miles in steady highway driving on a fast fill. The noise you heard might have been the relief valve on the high pressure regulator. The regulator (which is mounted on the frame rail near the rear of the drivers door has a PRD (pressure relief device) mounted on it to prevent high pressure NG from bypassing the regulator and getting into the intermediate pressure system. This is usually caused by the regulator sticking either by mechcanical failure in the regulator, or by the regulator freezing. It is getting cold enough right now to start seeing freezing at the regulator. Next time you run on CNG, listen for any noise from the regulator. The PRD usually "pops" when it goes off, not a PPPSSSSSS. The sound you are hearing may be a leak in the system in the area of the regulator. When you shut off the vehicle, the main gas valve (HPL) shuts off and then any excess stays at pressure. A fairly large leak would bleed off in a few seconds. Two things to check with the van running. First, find and check the high pressure regulator. With the vehicle warmed up, the regulator top cover (where the single line from the back of the van enters) should be warm to the touch along with the rubber hoses going to it. Next, with a spray bottle filled with soapy water, spray the regulator, lines and fittings in the area you heard the PPPPSSSSS and look for bubbles to see if anything is leaking. This includes the PRD on the regulator. You should not smell any "hint" of NG while driving.
          Yep, I'd have to hear the noise it made again to make sure..but when I turned the key off the first sound was "loud" almost made me jump...so it could have been more of a POP..but it was definitely followed by just a second or two of PSSSSSSSSS. Also...as another note....when I came out and started her back up when I was done with work I turned the ignition key to the acc position and heard just a very quiet, small PSSSSSSS from that same general area. then it stopped

          That's all I got for now.

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          • #6
            Re: 2002 Chevy Express 3500 CNG fill up ????????

            You have a leak. Don't operate the van on CNG until you find it and fix it. Under the hood by the drivers side fender is a fuse box. Take the cover off (it's kind of hard to work it around to remove it) and remove the fuse listed as "CNG". You will find it by referring to the cover for a layout---It's a yellow 20 amp fuse which should be the farthest to the right and the front of the vehicle when looking at the fuse box from the top. This will disable the CNG system and still allow normal gasoline operation till you can fix the problem. You will need to replace the fuse to test for the leak. Have a friend turn the key on while you are under the vehicle in the area of the high pressure regulator. Each time you turn the key from off to run, the high pressure lockoff valve will open allow a one second shot of CNG to fill the system. Find the leak (most likely the HPR) and repair it.

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            • #7
              Re: 2002 Chevy Express 3500 CNG fill up ????????

              LOL....ok, but there's a leak....the CNG has leaked out. I am using the van, but it's running on regular unleaded right now..like I said, I couldn't run on CNG right now if I wanted to....if I filled it again, it would just leak out again anyway.

              Anyway, I have it scheduled to go in for service this Wednesday to the Honda Dealership..where they have 3 actual CNG mechanics.

              If it is the HPR, about how much will this be to replace/repair???

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              • #8
                Re: 2002 Chevy Express 3500 CNG fill up ????????

                If it is a GFI part number P101-100 I have a new one that i am not using.

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                • #9
                  Re: 2002 Chevy Express 3500 CNG fill up ????????

                  The regulator on the van is a Impco regulator, not a GFI. It is GM specific, however Impco sells a regulator that looks like it but has a different port configuration that should be easy to change on the van. If I remember the Impco is a HPR-3600 and the GM regulator is a HPR-3600 GMC (suprise!) The regulator inlet might be smaller on the replacement regulator then the one on the van, however the fitting that is on the inlet can be swapped from the old regulator to the new one.

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                  • #10
                    Re: 2002 Chevy Express 3500 CNG fill up ????????

                    Gap....I'd gladly take that regulator off your hands if it'll work for my vehicle. Just send me a PM.

                    Thanks

                    Comment


                    • #11
                      Re: 2002 Chevy Express 3500 CNG fill up ????????

                      Hey guys...well you said you'd like an update..so I have one for you.

                      Just got back today with my van from the Honda Dealer..as they have a couple CNG "certified" mechanics that work on CNG stuff all the time....Everything in the system checked out OK...regulators in good shape, etc.

                      They also FOUND the problem. Off the regulator there is a hose that runs from the high pressure side to the "vaporizer" in the engine compartment...anyway, this "gas line" is about 3 feet long, and 12 inches of it, coming out of the regulator is black rubber. This was rubbing on the frame and wore a spot in the hose until it leaked. OK, I can deal with that..let's repair it...NOT SO FAST. GM has evidently discontinued this part, and the guy said, even if he COULD get it, I probably wouldn't want to pay for it..as it was $890.00 !!!!!! SERIOUSLY????? for a gas line that is 12 inches of black flex hose, and then the last 2 feet is stainless steel. THAT IS HIGHWAY ROBBERY right there.

                      So...my question to all of you guys...How can I best repair this? Can I just cut out the hose section that has the hole, and slip in a nipple fitting of some sort, and clamp each side???

                      Any thoughts, comments, or HOW TO's would be most welcome...or maybe if someone knows where I can get this part, for WAY LESS than the original LIST price.

                      Thanks
                      Dan

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                      • #12
                        Re: 2002 Chevy Express 3500 CNG fill up ????????

                        You could try to find the part from someone parting out a van. Unfortunately, junk yards don't take the time to remove lines and therefore they are usually destroyed. The line in question runs from the high pressure regulator to the low pressure lockoff valve which is mounted in the back of the doghouse. There is no "vaporizer" on a CNG vehicle---I hope Honda isn't providing them on GX's! If it were my vehicle (and the original part was unavailable), I would go to the local Parker hose distributor and have him make up a replacement hose. Parker carries a line of CNG hoses and should be able to get the "O" ring face seal fittings you need for the hose ends. He might even be able to swedge the stainless and flexible hose back together saving you the cost of a longer hose. You are only dealing with working pressures of between 85 to 120 psi on that part of the system. 250 is max psi as that is when the PRD will open. It won't be cheap but far less then $890. I have no idea of what the hose costs per foot but I just bought 10 feet of 5/16 gasoline fuel line and about passed out when the bill came to $47.00---so don't be in a panic when someone quotes you the cost. BTW--did the dealer check "Vintage Parts" to see if they had it? They buy most of GM's old obsolete parts inventory for pennies on the dollar and then resell it for dollars on the pennies. While you have the doghouse off, you should inspect, no replace, all of the rubber vacuum hoses on the engine. They really get hot under there and any cracked, leaking hoses can really mess up the operation of the CNG system. Also make sure the plastic adapters between the throttle body and the CNG distributor assembly and the one from the CNG distributor and the air cleaner are not cracked or leaking. It's also a good time to change the distributor cap and rotor as they are a problem on this model.

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                        • #13
                          Re: 2002 Chevy Express 3500 CNG fill up ????????

                          wow..thanks for the quick response...so do I take the entire hose off and take it in? How do I find my local Parker distributor? can you tell me the GM part number for this hose? Also what size fitting is it that goes from the flex hose into the regulator? can't I just reuse the original fitting, and splice in a new piece of flex line? like some LP gas line line???

                          Does "vintage parts" have a website? Is this something I could look up??

                          Thanks again

                          Dan

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                          • #14
                            Re: 2002 Chevy Express 3500 CNG fill up ????????

                            Doghouse = interior engine cowl/cover right?
                            Last edited by flyweed; 10-17-2012, 07:54 PM.

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                            • #15
                              Re: 2002 Chevy Express 3500 CNG fill up ????????

                              I went to one of the many Vintage Parts sites and found this listing for CNG hoses..but have no idea which one it might be..here's the link

                              http://www.vpartsinc.com/search?manu...de=starts_with

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