96 contour plug arking/rough iddle issues

[merlin1977]

Ok 96 contour runs great on gas, just installed a new gfi reg. when connected a plug wire test light noticed major arking at the plug on cng. using auto light double platinum plugs, new plugs,wires, and coil pack. does not do this on gasoline. I cannot figure out why on cng it would ark and on gasoline it would not. please any help would be appreciated

[smartineau]

Re: 96 contour plug arking/rough iddle issues

cng requires higher kv to fire and will significantly increase misfire problems. What is your plug gap, suspect it is .048 - .052, try running at at .036 to .042 Did you use dielectric grease on boots? Have you verified good contact with the clip inside on the spark plug ends. Anything like that will cause a miss on cng and not on gasoline.
Stan

[larrycng]

Re: 96 contour plug arking/rough iddle issues

Reducing the gap will help. Sounds like a boot problem or carbon tracking down the plug insulator. Once they start arcing you should probably replace them on a CNG applications.

You should not touch the plug porcline with your fingures the oil in you skin can cause carbon tracking (from John Deer CNG engines). Alcohol is a good cleaning agent. Use a clean dedicated magnetic plug socket - the carbon in the rubber in a regular plug socket can carbon tracking. And of course don't use piece of vacuum hose to start the plugs.

As was said the voltage requirements to fire a CNG mixture are significantly higher and sometimes require extra care.

larrycng