Hard starting on CNG - Cavalier

[Going Natural]

This isn't really a big deal to me, just more of an annoyance. Both of my Cavaliers are hard starting on CNG but on the rare occasion when the CNG is out, they start so easily on gasoline. Has anyone installed a momentary interrupt switch on the 20 amp CNG breaker? It seems like it would be very easy to have a push button interrupt switch under the dash to solve this idiosyncrasy of such an economically fantastic car. Am I crazy?

Thanks.

[siai47]

Re: Hard starting on CNG - Cavalier

It's the nature of the beast. If you read the CNG owners manual supplement it points this fact out. Because the Cavalier uses a fumigation system to supply the CNG and it requires some engine vacuum to start the CNG flow, starting takes longer. Many times the car will try to start and then stall---If your car is prone to this, just keep the starter running until a little longer until it is running smoothly. Also because engine vaccum is very low during cranking, it is important that all fittings, gaskets, seals, etc. in the intake system are tight and not leaking. BTW if your car is subject to the "thermal event" recall and it hasn't been done, get it fixed before you run the starter for longer periods of time then a normal start.

[Sam Taylor]

Re: Hard starting on CNG - Cavalier

I am not sure what should work best in starting. My Cavalier takes two to three and sometimes four start attempts on cold mornings. The cg manual says to give it no gas at all on a start. The Chevy dealer says to give it about half an inch of gas on the pedal. This has nearly never worked for me. Usually on the first attempt I give it no gas and it starts up half the time. When it does not work on the first attempt I put the pedal to the metal for the second, third or fourth time. I have only run down the battery once in the past two months. I worry about the poor starter. Should I be doing something different here? On gasoline it always starts with the first attempt with not touching the gas pedal. After an engine warm up, it starts easily without touching the gas pedal in the natural gas mode. Would it help to replace the low pressure regulator? The car is a 2001 with 40,000 miles. The Chevy dealer, checking out the computer codes, thinks there is nothing wrong with the car.

[Lancer Automotive Group]

Re: Hard starting on CNG - Cavalier

We had a Cavailer in our shop last week with the same problem; he had a small pin hole in the diaphragm allowing the system to purge so on starting it would have to recharge the fuel line.

[siai47]

Re: Hard starting on CNG - Cavalier

Sam, you need to crank the engine for at least 8 seconds before you give up trying. If the engine cranks longer than that, it will start on gasoline even if you have CNG in the tank. Do not push the accelerator pedal when cranking or try multipule attempts--it builds up gas in the induction system an sometimes blows your air cleaner off . If the car does start on gasoline, it will quickly change to CNG the first time you let off on the accelerator after you start to drive. Check for leaks in the low pressure gas system and the intake system. If you think you have a regulator problem, it needs to be addressed.

[siai47]

Re: Hard starting on CNG - Cavalier

Sam, you need to crank the engine for at least 8 seconds before you give up trying. If the engine cranks longer than that, it will start on gasoline even if you have CNG in the tank. Do not push the accelerator pedal when cranking or try multipule attempts--it builds up gas in the induction system an sometimes blows your air cleaner off . If the car does start on gasoline, it will quickly change to CNG the first time you let off on the accelerator after you start to drive. Check for leaks in the low pressure gas system and the intake system. If you think you have a regulator problem, it needs to be addressed.

[Lancer Automotive Group]

Re: Hard starting on CNG - Cavalier

Cavalier is fixed, had a small tear in the diaphragm. We rebuilt it and we cleaned the Mass Fuel Sensor. Running great now, customer has is up for sale, let us know if your interested.

[bufordthelittle]

Re: Hard starting on CNG - Cavalier

Cavalier is fixed, had a small tear in the diaphragm. We rebuilt it and we cleaned the Mass Fuel Sensor. Running great now, customer has is up for sale, let us know if your interested.

Lancer Auto, could you give me a ball park figure of how much it costs to rebuild the diaphragm?