new user with bi-fuel 04 cavalier

[04CNG]

Several questions but first question is what type of gasoline to use in bi-fuel car if I intend to only use gasoline every 60days.
100% gasoline or
10% ethanol
Does any one know what manufacture recommends?


2nd?
Ran long trip on cng only ~400miles
Was running low on cng less than 1/4 tank and car died but started right back on cng.
Anyone with this experience?

Thanks in advance for any help

[siai47]

Re: new user with bi-fuel 04 cavalier

Pure gasoline with no ethanol (if you can find it) is your best choice. Ethanol does not play well with gasoline and deterioates quickly in storage. Run the car until it is out of CNG and then run it low on gasoline. Add a product like Sta-bil (auto parts stores, Wal-Mart, etc.) to the gasoline tank when it is nearly empty and then refill it. Allow the engine to run on gasoline for a short time and then refill with CNG. Every 100 starts, the car is programed to start on gasoline and then switch to CNG just to purge the gasoline fuel system. 1/4 tank of CNG changeover to gasoline is incorrect operation of the system, unless you were low on fuel, driving at high speed and then shut the car off. When you restart with less then 600 psi in the tank it will switch to gasoline and then not switch back until you are above 600 psi. In normal operation, you should be able to continue on CNG until the tank pressure drops below 250 psi at which point the fuel gauge should be on or below "E" and a check gauges warning light should be on. BTW 600 psi is well below 1/4 of a tank so if it keeps doing this, something is amiss . I also noticed in your post you "ran long trip on CNG only ~400miles". This is not possible with the standard Cavalier. It will only run on average 150-160 miles on CNG, 180 tops. If you got one that runs this far on CNG hang onto it forever!

[04CNG]

Re: new user with bi-fuel 04 cavalier

Sorry for my mis-quote
Ran ~319miles on cng with several fills as Oklahoma has more stations than most
Hope this clears up my mistake

Also the car "died while on cng" after about 275 miles and "re-started
and ran on cng" until system was empty of cng then switched over to gasoline
Sorry tried to be clear
Guess I need to go back to English 101

Thanks for you reply
Good suggestions

[siai47]

Re: new user with bi-fuel 04 cavalier

The only thing I can think of is a freeze up at the high pressure regulator. Just as the tank gets hot when filling, it gets very cold when using the gas. The faster you empty the tank, the colder it gets (i.e. driving at freeway speed). The regulator itself can freeze, usually at the porous inlet filter. The regulator is heated by engine coolant to prevent this. However, if there is moisture in the gas it may still plug the filter. When the car changed to gasoline (or quit running) it would allow the ice to melt thus allowing the car to run on CNG again. The '03 and '04 Cavaliers also have an additional filter that needs to be drained periodically. If this sounds logical, check and/or replace the filter in the high pressure regulator, replace the intermediate pressure filter and drain and clean the filter bowl. Finally check the coolant lines running to the regulator to be sure they are getting hot when the engine is running. There are threads on this forum that show how to do most of the maintainence items. Parts are available from GM although you may do better at a forklift dealer for the regulator filter and a Parker-Hannifin dealer for the intermediate filter. If you want to work on your car, you should buy the CNG service supplement from GM, or check with people that sell literature on E-bay. 2003 or 2004 supplements will work .