Cavalier question

[goodforyou]

What are the top 3 usual reasons a cng vehicle (cavalier) won't take a fill when the cng tank is empty?
(It is in gasoline mode and the light on the indicator is lit showing show also)

[CNG MOTORS]

Re: Cavalier question

The only reason is because it is already full. Assuming no tampering or modifications. Why you won't run on CNG is another matter. Transducer could be a culpret. Cavaliers have a high failure rate of the mass gas sensor 2002 and older. But what to check first is the 20 AMP fuse located in the fuse box under the hood on the driver's side fender, it will be the only 20 AMP fuse in there.

[goodforyou]

Re: Cavalier question

The fuse seems to be okay. The gas mass sensor thing bothers me. I can't believe that a car that only has 20k miles on it is experiencing problems like this. It's a 2001, we're not the original owners, so more than likely, no warranty.

Is this something that you can run down to auto zone and hook it up to the OSII thing or is this something that for results a dealer/certified tech needs to do?

[CNG MOTORS]

Re: Cavalier question

gass mass does have an OBDII code that can be read by a scanner but not all failures will generate a check engine light.

[goodforyou]

Re: Cavalier question

The check engine light only comes on while running on regular gasoline.

[freedml]

Re: Cavalier question

How about something simple, like the filler check valve is rusted shut? Some of these vehicles may never have been run on CNG. Is there any CNG pressure anywhere in the system?

[nttrainer]

Re: Cavalier question

I can't believe that a car that only has 20k miles on it is experiencing problems like this.

It may sound like backwards logic but one reason the car only has 20k miles on it is that nobody wanted to drive it in the government agency that originally owned it. I've often seen two cars from the same agency at an auction, one with a lot of miles and one with relatively few miles. Inevitably, the car with the higher miles drives better than the one with low miles.

The people knew which motor pool cars drove well so they would always choose that one.

[goodforyou]

Re: Cavalier question

It wasn't a pool car. This one was with the US Navy and it belonged to an individual. We were lucky (?) to have come upon it.

[siai47]

Re: Cavalier question

If you could, try to keep your questions about this car in one thread. It is hard to chase your problem around through several different posts . Everything still appears to be related to a bad GMS. Have you tried to find one on E-bay, contacted other members on this fourm or responded to the PM sent to you? Just trying to help .

[CH-4]

Re: Cavalier question

How about something simple, like the filler check valve is rusted shut? Some of these vehicles may never have been run on CNG. Is there any CNG pressure anywhere in the system?

I agree. Most Cav's only ran on gasoline, so it may need a new P36 fill connector. Read the manual also for filter and seal replacement.