Gas Smell

[Philster]

I just purchased a 1999 Chev Cav CNG and when I pull it in my garage, I get a Nat. Gas smell coming from under the hood. I have narrowed it down to the area under the air cleaner. How is the best way to find the leak? I leave it outside and in the morning I can't smell anything so I am assuming that I have a small leak that drains my fuel line. Any suggestions would be appreciated.

[Highmarker]

Re: Gas Smell

Philster,

I have moved your thread into the GM/Chevy Vehicles forum so that those with GM/Chevy expertise can chime and answer your question. Here is what I know:

It sounds like your problem is coming from the Low Pressure Lockout (LPL) or the Low Pressure Regulator (LPR). The LPL is located just before the LPR, it is a small solenoid in the CNG line. The LPR is the large cylindrical part on top of the engine. You can spray some soapy water on the LPL and see if it creates bubbles. Bubbles = Leak; No Bubles = No Leak. If either one is leaking, they need to be replaced. You can get a replacement kit for the LPR on the internet.

[kirkbenge]

Re: Gas Smell

My brother had a similar problem. Check out this post(Smell gas in 2001 Cavalier) for some useful information and links regarding where you can get parts etc.

[Yroc]

Re: Gas Smell

Is that a fumigated system or port injected? If it's fumigate and you are smelling it through the air filter, then that is normal. You can check all your connections with soapy water to make sure you don't have a leak, but it sounds like you are smelling it through the air filter? That should just be the gas left in the hose that runs from your regulator to your intake.

[Philster]

Re: Gas Smell

UPDATE:

It appears that the smell is only present after I fill the car up on my way home. The two days that I filled up in the morning before driving my 100 mile commute, I did not have any smell. The two days that I filled up just before returning home, the smell was there. If this is the case, I will just fill up in the morning. I have checked the line connections that are below the air filter and cannot see any leak, and the smell is only present by the air filter. My main concern is that I have my boiler for my home in my garage and I really don't want to expand my garage through an explosion. Is it possible that the fueling station that I use overfills my tank or something like that?

Thanks for your input, I really am enjoying driving and paying for the fuel for my car.

Philster

[siai47]

Re: Gas Smell

The only thing I can think of (beyond the obvious, its normal) is that the low pressure lockout valve is not seating and allowing pressure in the line between the HPR and the lockout valve to bleed through the low pressure regulator and out through the air cleaner. Only a guess

[Philster]

Re: Gas Smell

Where would I get a Low Pressure Regulator valve?

[kirkbenge]

Re: Gas Smell

It sounds like it's probably fairly normal. I get a small whiff of gas about 30% or 40% of the time when i park my car in the garage, if the timing is right. It seems to be that If I park in my garage for the night, I can never smell anything in the morning, but if I park in the garage and then go to get in the car an hour or two later, I can smell a whiff of gas about 1/3 of the time. This seems to be coming from my air filter, as what's left in the line bleeds out. It certainly isn't very strong, as I usually only catch a whiff, and I would need to sniff around the car to smell it again.

Just remember that your nose is VERY sensitive to mercaptan (the chemical that gets added to NG to give it that smell). The human nose can detect methyl mercaptan at concentrations as low as 0.002 ppm! That is WELL below a dangerous level. If you are dealing with a significant leak, or a dangerous level of gas it will typically smell very strong. If what you are smelling is an "occasional whiff" and no leaks are detected, then it probably isn't an issue. I once traveled in a car with a leaking LPR and the gas smell was very strong, even nauseating while in the car. When that car was parked in a garage, the smell was quite strong and unmistakable, despite the fact that the leak would stop when the car was turned off.

KIRK

[Lancer Automotive Group]

Re: Gas Smell

If you want to bring it by our shop we can use our sniffer to see if we can find a leak (no charge for the sniffer). Just give us a call.

[Philster]

Re: Gas Smell

If you want to bring it by our shop we can use our sniffer to see if we can find a leak (no charge for the sniffer). Just give us a call.

Where are you located?

[Lancer Automotive Group]

Re: Gas Smell

3687 South 300 West
Salt Lake City UT 84115
801-268-8863
http://www.lancerautoand4x4.com/

[Philster]

Re: Gas Smell

Does anyone know where I can buy CNG parts. If I need a low pressure lockout valve, I don't know where I can buy one. Please let me know if there are good online resources.

Thanks

[Lancer Automotive Group]

Re: Gas Smell

We carry Advanced Fuel Components parts, they have a lock off that may work. If your in the area stop by and one of out techs can take a look.

[awood]

Re: Gas Smell

All the above info is good and accurate as far as I know. Permit me to share my experience with my 2000 Cav... I had a smell that was very strong coming from under the hood. I could smell it while driving as well. It was more pronounced when my face was just over the small vent holes for the low pressure regulator. After reading here on the forum, I tried some leak detector solution (soapy water) over the vent, and there were many bubbles, indicating a leak. After replacing the diaphragm in the regulator (rebuild kit), I now had no leak at the vent on the LPR, but I could still smell the gas while driving. Then one day when refilling the tank, I heard a very loud pop from under the trunk area, followed by a loud rush of "air" (CNG). It seems like I had a dual problem with both the LPR and the HPR (High Pressure Regulator). The HPR must have been leaking as well, since the smell went away after replacement.

Bottom line...if someone has a sniffer, that would likely solve a lot of guesswork. If you don't want to go that route, just follow a process of elimination. You may be able to find some commercial leak detector solution that will indicate a leak better than soapy water. Keep your mind open. It could be just about anything. I had a smell inside, even though the HPR is in the back of the car, just above the muffler.

[Philster]

Re: Gas Smell

Great news. I called my local Chevy dealer and they ordered me a low pressure lockout valve and I put it on in about 30 min. It cost around $110.00 but the gas smell is GONE and what is better, the car starts immediately. No more cranking and waiting. Thanks for all the great info. This car is not only paying for itself in savings, but last month it put around $80.00 back into my pocket.

Philster