2002 cavalier leaking under hood during refuel

[rguzek]

Our 2002 cavalier will not run on cng. The only symptoms include a check engine light and it is making a hissing sound under the hood when we are refueling it with CNG. I assume this is a leak. I tried soapy water all around the area of the sound but I couldn't locate the leak with any certainty. I can push gently on the air intake manifold and make the sound stop, which is odd, the car isn't running during this. It's only refueling. I also think it is doing this when it is running on gasoline. I'm pretty sure I can hear that same hiss over the engine noise.

The only thing I picked up from the repair manual that might help me understand this is that the low pressure lock off (LPL) and the high pressure lock off (HPL)should both close and prevent gas from flowing to the engine when the car is off. I think they are both controlled from the same source also. I think gas is flowing all the way through the system to the engine and back up into the air intake manifold??? I don't know much about engines. Does anyone have any ideas or experience with this?

[TheBundo]

Re: 2002 cavalier leaking under hood during refuel

Sounds like 2 issues if you can press on the manifold and make it stop. One is that your manifold is leaking, and secondly that there is pressure in the manifold at all with the engine off (or even when on, should be a vacuum).

[siai47]

Re: 2002 cavalier leaking under hood during refuel

When you are refuling, the line going to the High pressure regulator is pressurized to the same pressure as the fill port. This is regardless of the High pressure lockout valve position in the tank. The low pressure lockout valve located on the top of the engine should stop gas flow during refuling. If you are getting a leak, put soapy water around the lockout valve and at the fitting on the back of the valve facing the rear of the car. The line that connects to that fitting goes directly to the high pressure regualator at the rear of the car. There is a short section that is braided hose at the end of the line near the low pressure lockout valve. I would suspect that your leak is at one of those two points.

[rguzek]

Re: 2002 cavalier leaking under hood during refuel

Thanks for all of your input. I will put some soap on the LPL and see what I get. We actually replaced this about two months ago. I'll let you know what we find.

[siai47]

Re: 2002 cavalier leaking under hood during refuel

Did you ever find your leak? It said in your last post that you replaced the LPL. Did you possibly loose the O-ring between the fuel line running from the rear of the car to the LPL? It fits in a groove in the fitting that is screwed into the LPL. The line then attaches to this fitting and the O-ring seals it. This would explain the leak you mentioned.

[rguzek]

Re: 2002 cavalier leaking under hood during refuel

We just finalized the rapair on this vehicle last Friday. We took it into our local Chevy dealer and he originally thought the low pressure lockout solenoid was bad (that's what the computer diagnosis gave him). He replaced it and then determined that the line from the tank to the engine had two small leaks in it just under the air manifold on the top rear of the engine. The gas line was originally installed too close to the engine components and it vibrated holes in it. Chevy replace the line and the vehicle is now functioning without issue. This repair process took several weeks. Sorry for the slow follow up.

[krnorth]

Re: 2002 cavalier leaking under hood during refuel

How much were your repairs from the dealer?

[wjdaytech inc.]

Re: 2002 cavalier leaking under hood during refuel

if you have a engine ck light a qualifyed mech, can scan, you need the proper scan equimpment to trouble shoot. the leaking could be a shut off valve, however a qualifyed tech should look at it, remember you are dealing with 3600 psi,cng, which won"t cause a small fire, explosion, it will cause a large one!! race7019