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chevy 2500 bi fuel problems

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  • #16
    Re: chevy 2500 bi fuel problems

    Variation learn procedure can be done on either fuel. Watching the fuel gauge drop and changeover to gasoline is a positive indication that the tank valve is closed.

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    • #17
      Re: chevy 2500 bi fuel problems

      Another symptom to watch for with Bi-Fuels is related to dirty or sticking CNG injectors. If you vehicle starts on gasoline, but is taking a longer than normal time to crank before it starts, you may have NG bleeding into the intake when it should be closed (sealed). In essence, you vehicle with try to start but may act like it is flooded. Ford has a service bulletin which someone posted within the forum, giving the details for cleaning CNG injectors. I have had good success with using cleaners for intake manifolds. We can't use the in-tank additives suggested for gasoline injectors beacuse that fuel never travels through the CNG injectors. It may take just a 'spritz' in each injector, let it sit for 5-10 minutes then run it on CNG as soon as possible to clear the stuff out. This does have three symptoms: 1) Rough Idle on CNG (or stalling near idle), 2) misfire codes on specific cylinders and 3) symptoms of flooding causing longer cranking times starting on gasoline.
      '11 Fusion Bi Fuel & FMQ2-36 VRA
      (Former owner '09 Civic GX)

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      • #18
        Re: chevy 2500 bi fuel problems

        Due to our oklahoma flood storm, I didn't get to test swapping coils yesterday. Hopefully today. I would really like to do the Tech 2 injector balance test but I wonder how it would present a leaking injector? Larger or random pressure drop I suppose. If I can't get acess to a TechII or person, I will probably clean/inspect the injectors anyway when I change the high pressure filter. It doesn't have any hard starting on gas or cng but the other two symptoms are there. Thanks for the input.

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        • #19
          Re: chevy 2500 bi fuel problems

          Bought two new coils and did some swapping around but to no avail. Still throwing cylinder 7 misfire. I also noticed tonight that that injector seems to be ticking much louder than the others so perhaps its the whole issue. So shut down the tank, bled the HPF and removed all the injectors. Going to send them off to be cleaned (whether they need it or not) ;-) . BTW, there wasn't much goo in the filter and it is very clean, with the exception of some black chalklike particulate on the plastic cartridge spacer. I'll new this up when I put the injectors back in.

          It will be a week or so for the service so I will post when I know more.

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          • #20
            Re: chevy 2500 bi fuel problems

            Well, the verdict was a bad injector on number 7! Both good and bad news given the priciness of those little darlings but glad to know there was a real issue. I sent mine to Ole's Carb and Electric and they turned them around in one day and shipped yesterday. I found a replacement for the bad one on good ole Yahoo for $260 and I should have them all back early next week. Next update when I get them installed.

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            • #21
              Re: chevy 2500 bi fuel problems

              hey question back to the 2500 bi fuel problem it looks like my injector is sticking. i tried all cleaners like intake manifold, carb, brake and it still sticks. is there a better cleaner to use or can I use some kind of lubricant to free it up?

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              • #22
                Re: chevy 2500 bi fuel problems

                How are you getting the cleaner into the injector? You could try something as simple as WD-40 to flush out anything that might be gumming it up. But you need to be able to pressurize the injector with whatever you are cleaning/lubing with while pulsing the injector at the same time. If it is really dirty, it should be ultrasonically cleaned.

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                • #23
                  Re: chevy 2500 bi fuel problems

                  Sorry to hijack, I am having a similar issue to my 02 2500 CNG. Just replaced the plugs with NGK TR5's and a set of MSD wires. It is a little better but not great. I am very new to CNG vehicles so not sure where to go. I did put a gauge on the CNG pressure test port and it was bouncing around 125psi on the rail. I also removed the filter under the cover to see if that would improve the problem but it did not. Not sure where to go from here.
                  Any info would help.
                  I would like to start a new thread but couldn't find a way to post new topic.

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                  • #24
                    Re: chevy 2500 bi fuel problems

                    Does cng require special spark plugs?
                    What brand do you guys prefer?

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                    • #25
                      Re: chevy 2500 bi fuel problems

                      Originally posted by ousoonerfan22 View Post
                      Does cng require special spark plugs?
                      What brand do you guys prefer?
                      I'm guessing it depends on the conversion... For the kit that was put into my 2000 Tahoe (I'm the second owner), I have an "owners" card that recommends one heat range higher. To be honest, I've done that, used regular plain Jane AC Delco, platinum, and even Iridium over the years.... and I can't tell the difference... again just a sample of one 5.3 liter Vortec with a fumigation system
                      2008 GX (extended range, trunkless version)
                      Polished Metal Metallic 2012 Civic Natural Gas
                      Fuelmaker FMQ-2-36 (since 2001)
                      Previously owned: 2000 GX (11 years), 1995 Bi-fuel Sonoma, 2000 Bifuel Tahoe, 2000 Bi-fuel F150

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                      • #26
                        Re: chevy 2500 bi fuel problems

                        I've been driving this truck the last 2-3 weeks and it was running rough,backfiring through the throttle body but would still run on cng.Now this week it stays on unleaded and won't switch over to cng.....what would cause that? I fill up at the local ONG and with the tank empty I can only get the tank to hold 4-5 gallons of cng.
                        The previous owner had the truck for about 2 years but only ran 2-3 tanks of cng in it because there was no place close to fill with cng.The truck is a '98 chevrolet 2500 with 132,000 miles and is an old ONG truck. Opinions or suggestions are welcome!

                        Brian

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                        • #27
                          Re: chevy 2500 bi fuel problems

                          Originally posted by hmdive View Post
                          Hi I am new here and have a question regarding maintenance on a 2004 chevy 2500 bi-fuel van. I have had it over 4 years and only occasionally had some rough idling when using cng, on regular gas it has always run really smooth. I recently moved out of cng fueling station range and for the last 5 months used only gas with 10% ethanol. I noticed that it doesn't start great lately and runs a little rough on gasoline sometimes. After reading other posts about changing the plugs, wires, distributer and cap I realized I am overdue for a tune-up. I bought this van with 112,000 miles and now have 178,000 miles and never changed the plugs. Do you have any suggestions for service when out of cng mechanics area. I called the gm dealer and they want over $550 to change the plugs, wire harness and remove any carbon tracings. Is this a job that must be performed by a dealership or can goodyear or firestone perform the same service for a lot less? I just worry that there are some special components, etc. that are specific to a cng vehicle and that they will unknowingly mess something up. Any thoughts? One more question, is there a fuse on this vehicle that needs to be unplugged if not using cng for extended periods of time?
                          to change the plugs on your 03/04 you'll need to remove the engine cover and replace the 8 plugs with ac delco pn 41-110.

                          to take off engine cover:

                          1. remove the passenger seat by taking out the 4 nuts that hold it down
                          2. the 4 screws in the center console below the cupholder to remove the center console.
                          3. remove the 2 screws in each right and left knee bolster to remove them
                          4. unbuckle and remove the engine cover

                          then twist the spark plug wires so you can yank them off. remove with spark plug socket, put in new ones with anti-seize compound and dielectric grease, put the spark plug wires abck

                          mines took about 2 hours to do.

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                          • #28
                            Re: chevy 2500 bi fuel problems

                            I had a similar problem with my 03 2500.I tried plugs/wires/coils and nothing. I'd seen similar problems with fords so I ended up removing the catalytic converters. Mine were totally burned and clogged up. Major improvement to the performance with the new Cats!

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                            • #29
                              I just purchased a 2013 Silverado 2500 HD with CNG we don’t have any place to fill the tank I removed the tank and plugged the line I now have and check engine light and code that says low fuel pressure has anyone else had this problem and how is it fixed

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