01 Cavalier

[wclx44]

Curt,

I take the liberty of asking you this question directly because of your expertise. Hope you don't mind helping me out.

I wanted to remove the filler tube + the check valve that goes between the fill valve and the tank. Seems easy to do because both ends are connected by compression fittings which can be removed by ordinary wrenches. I plan to loosen the fitting next to the tank to let out the gas before fully decoupling it. My question is, can I safely do this? I'm not concerned with any risk of fire but I'm unsure of any danger from the 400 psi residual pressure that may still be in the tank.

Thanks, Curt!

wclx44

[siai47]

Re: 01 Cavalier

This is easy to do. If the CNG system is still working you can bleed off the residual pressure. Open the trunk and locate the little pigtail connector with a single wire (I believe it is orange). Seperate the connector and start the car. It should run on CNG for a few seconds and then switch over to gasoline. You will also get a check engine light which will go away after three ignition cycles after the wire is reconnected. This will drain the system of fuel downstream of the high pressure lockoff including the fill line. Leave the connector off until you are done with your work. If the car is not able to run on CNG or to varify the pressure is bled off (and to get the last 200 psi off the high pressure side) crack the fuel line going into the low pressure lockoff under the hood until all pressure is released. None of the fittings are compression fittings, they all have "O" rings in them. Be sure to check the condition of the "O" rings and lube them with silicone grease before reinstalling them.

[Curtis]

Re: 01 Cavalier

I personally don't recommend anyone not certified to work on the fuel system to actually open the system due to the inherent risks. Those that do so, do it at their own risk. That said, members who do work on their own vehicles state that the proceedure they use is to run the vehicle until it runs out of fuel to relieve tank pressure. Then bleed off residual line pressure before attempting to decouple anything in the fuel system.

Saia47 seems knowledgeable about the process, although I don't know what his specific knowledge base is. I would recommend anyone working on their own car to obtain a shop manual as a reference for the factory recommended proceedures.

You noted what type of vehicle you are wanting to work on, so the process, although possibly similar among cng vehicles in general, may vary from model year to model year. What wire color to disconnect might not be the same on various years of Cavalier.... I don't know specifics about the Cavalier.

We do not like to give out repair proceedures here on the site. The liability issues are huge and we don't want to see anyone get hurt. I highly recommend letting a cng certified mechanic do the switch out for you. If you apply the information provided by other members of cngchat, be mindful that you do so at your own risk.

[wclx44]

Re: 01 Cavalier

Thanks, Siai47 and Curt, for your good answers. Excellent advices from both.

I stand corrected to call the fittings with "o" rings as compression fittings. I also left out an important condiion: the car is non-operational. I'm trying to remove the stainless tube leading from the filler valve to the tank.

Before the car became inoperable, it has cycled through 2 tanks of regular gas without using cng. So I know there isn't much left but residual pressure.

Thanks again!

wclx44