Bad Gas leak- 2000 cavalier

[ssybert]

Hello Everyone,

I have a 2000 cavalier bi-fuel. When on CNG it's got a terrible gas leak... so bad that if I turn the heat on it stinks so bad it gives me a stomach ache. I can smell it outside the car as well. I tried smelling the little screen ontop of the regulator and originally thought it was that. After further investigation, it looks like it's a device close by. the picture shows the device I'm referring to. I'm pretty sure this is where it's coming from.

My questions are:

What is this thing?

Is it safe to work on these lines just by turning the car off or is there an emgergency shut off I should activate somewhere?

There is a yellow capped, A/C charge looking thing on this line. Should I bleed this first?


Thanks guys. Any help to keep me from blowing myself up trying to fix it would be great

Scott

[Harpoon]

Re: Bad Gas leak- 2000 cavalier

That is the lower pressure solenoid that turns off the lower pressure gas line when the ignition is turned off. In the service manual it is called the Lower Pressure Lock-off (LPL). To verify this is leaking I would mix some soapy water together and spray the LPL and watch for bubbles while the engine is running. The most come failure is the LPR (Low Pressure Regular the round thing with the screen on top) gasket fails and causes the oder in the engine compartment and through the vent.

The yellow (bleed line) is actually the 150PSI test port that is used to verify the pressure is good from the High pressure regulator to the low pressure regulator. It is used for diagnose the system.

Steps to work on the LPL
1) Relieve the CNG fuel system (this varies from 98 to 99+ in 98 there was a emergency shutoff under the drivers side rear door) I only have the 98 manual and this doesn't apply to the 2000.

I would assume the procedure is the same exepct instead of closing the valve under the car you close the valve on the High Pressure Lock-off (HPL) using a hex wrench. Once you close the the valve then you proceed to start the car 5 times (gasoline starts) this relieves the 150 PSI pressure to the Lower pressure regulator.

Once the 150 PSI is relieved these are the steps.
1) disconnect the negative battery terminal
2) remove the air cleaner assembly (I wouldn't do this)
3) disconnect the fuel line to the LPL

If the LPL doesn't make bubbles while running on CNG then I would recommend rebuilding or replacing the LPR. The rebuild kits for the LPR run ~$125 or so from Alternative Fuel Systems Inc. The rebuild kit part number is RK-PEV-2

-Harp

[ssybert]

Re: Bad Gas leak- 2000 cavalier

Harp,

Thanks for the tips on tracking this leak down. I did just what you suggested and used a bottle of soapy water to find it. It turns out, that part I suspected, was indeed the leak. The red/brownish huge nut looking part has a hairline crack on the back of it. It looks like it's seaping right through the metal. Do you happen to have a blowup of this part? Can I buy just this huge nut thing or do I have to buy the entire assembly? It looks like one side of it's electrical (which seems to get pretty warm via electricity pretty quickly) and the other side is mechanical.

Any help with this would be great.

thanks again,
Scott

[Harpoon]

Re: Bad Gas leak- 2000 cavalier

I wish I had a part number to provide you with, however the repair manual sucks when it comes to part numbers. I would suspect you will have to replace the whole assembly. If anyone has the part number please post it to the thread as mine is leaking as well

-Harp

[ssybert]

Re: Bad Gas leak- 2000 cavalier

Did you discover the leak after I explained where mine was, or was this already a known issue?

Scott

[ssybert]

Re: Bad Gas leak- 2000 cavalier

Harp,

I called up my Chevy dealer and tracked down the part name and number.

It's #11 on the GM parts department blowup illustration (page ID: MJ03-027)

The name of the part is 'CNG Pressure Shutoff Valve'

The part number is '52368527'

The price my dealer gave me is $104.69

I plan to try and repair it with a JB Weld first. I doubt it's going to hold that kind of pressure, but I'm going to give it shot anyway.

Scott

[siai47]

Re: Bad Gas leak- 2000 cavalier

For the cost of the valve, I would just replace it and be done with it. JB weld might stop the external leak, however, if the valve is cracked all the way through, the valve seat may not be working either. In any event, there is no reason to risk leaking gas into the engine compartment at 150 psi when you are driving if the JB weld fails. Install the new valve, check it for leaks and be done with it. P.S. a couple tanks of CNG will pay for the valve anyway.

[ssybert]

Re: Bad Gas leak- 2000 cavalier

I took a close look at it again in preparation for my cheap-o fix and realized, I'm not fixing this. We're talking hairline cracks in a high-pressure gas valve with less than 1/8" of area to work in to spread the goop.

Forget it... GMPartsDirect has it for like $65.00. I'm ordering one now.

[ssybert]

Re: Bad Gas leak- 2000 cavalier

For the cost of the valve, I would just replace it and be done with it. JB weld might stop the external leak, however, if the valve is cracked all the way through, the valve seat may not be working either. In any event, there is no reason to risk leaking gas into the engine compartment at 150 psi when you are driving if the JB weld fails. Install the new valve, check it for leaks and be done with it. P.S. a couple tanks of CNG will pay for the valve anyway.

Oh.. and a couple tanks of CNG wont cover it in my neck of the woods. On the east cost there is only ONE CNG station within a tanks worth of driving... lucky for me it's on the way to work . It's still $2.56GGE though

[DannyCNG]

Re: Bad Gas leak- 2000 cavalier

I have a strong feeling I have the same problem with my
bi-fuel chevy lumina. $65! That makes me happy!

[Hughes]

Re: Bad Gas leak- 2000 cavalier

Steps to work on the LPL
1) Relieve the CNG fuel system (this varies from 98 to 99+ in 98 there was a emergency shutoff under the drivers side rear door) I only have the 98 manual and this doesn't apply to the 2000.

I would assume the procedure is the same exepct instead of closing the valve under the car you close the valve on the High Pressure Lock-off (HPL) using a hex wrench. Once you close the the valve then you proceed to start the car 5 times (gasoline starts) this relieves the 150 PSI pressure to the Lower pressure regulator.

Once the 150 PSI is relieved these are the steps.
1) disconnect the negative battery terminal
2) remove the air cleaner assembly (I wouldn't do this)
3) disconnect the fuel line to the LPL

-Harp

Are these steps the same for my 2002?

I have a new LPL and am planning using it to replace the old one. If I run the thing out of CNG is that a good idea too?

Also, you recommend using thread "Tape" sealant on the threads?

[siai47]

Re: Bad Gas leak- 2000 cavalier

There is no reason to run the car out of CNG, remove the air cleaner, close the HPL manually or disconnect the battery terminal. There is a single connector in the trunk located near the drivers side end of the tank. Disconnect that connector and start the car. The fuel gauge will drop like a rock and it will switch over to gasoline. Removing this wire prevents the HPL from opening relieving the fuel from the HPL to the HPR. It also verifies the HPL is working and shut off fuel to the rest of the system. Manually closing the HPL is a pain compared to removing the electrical connector. There is no way to completely relieve the intermediate pressure line without some gas escaping. Just loosen the tube nut at the LPL and allow the gas to escape. The fittings that are pipe thread style should be sealed with liquid sealant, not tape. Teflon tape sealant tends to grind itself up into little strings that can get caught in things like lockoff valves and regulators and therefore should never be used. Some of the fittings are equipped with "O" ring face seals. These can usually be re-used and need to be lubricated with Vasoline before assembly. Never use sealant of any type on these fittings. If you have a bad seal and need to replace it, you must get one from the dealer. It looks like an "O" ring but it is a 1/4" ORFS instead. It should be GM part # 52368711. After you get the car back together, reconnect the connector in the trunk to restore CNG operation. Start the engine and check all fittings for leaks with soapy water. You should have a "check engine" light caused by starting the car with the connector removed. This light will clear itself after three ignition cycles or you can remove the battery ground terminal to clear the code.

[Hughes]

Re: Bad Gas leak- 2000 cavalier

Ok... I'm going to run and get some liquid sealant from the auto parts store for the threads.

I ended up running the tank empty anyway. I understand there's still a bit of cng in there right? So, I'll do the wire disconnect thing, and disconnect the negative terminal.

Looks pretty straight forward from there.

Thanks so much!

[siai47]

Re: Bad Gas leak- 2000 cavalier

Whoa! Don't disconnect the negative terminal until you have started the car after you disconnected the connector in the trunk. You must bleed off the high pressure to minimize the amount of residual CNG in the system. If you don't do that, it isn't dangerous except you will have more gas to get rid of. If the tank is out of CNG you will only have about 200 psi to deal with anyway. Be sure you keep track of all the face seals, lube them with Vasoline and make sure they stay in their grooves when re-installing.

[Hughes]

Re: Bad Gas leak- 2000 cavalier

Check... thanks for you quick reply. :-)