Do glow plugs do this?!

[BradZ_09]

Hey all, bashin my buggy at he local dirt jumps, great fun Anyway, buggy died, had half a tank left, and it was a total A-Hole to start again, didnt seem to prime no matter what i did, more air in the line not enough fuel, i took the plug out, and the coil was black. but when you look straight down the plug, the ring around it is black aswell, I'm assuming the means its hell rich?
I think its a HSN issue as i leaned my LSN not too long ago and after puttin a bit of spit on the head after running it instantly sizzled, meaning its too hot, so id say the LSN is fine. Any suggestions?
Plug has a good solid glow, but ill change it soon

 

[chelseafc385]

this should have been posted in the general nitro talk section

 

[olds97_lss]

What were your head temps at the time you tried to restart? How old is the engine (how much fuel has been through it)?

A lot of times, a hot engine doesn't like to start right away until it cools down. In those instances, I hold the throttle wide open and pull the starter quickly 4-5 times and it usually gets enough fuel through it to stop the vapor lock in the carb.

This also happens as an engine is beginning to wear out. They will run, but once hot, they don't like to start until cooled off due to lack of compression when everything is expanded due to the running temps.

 

[BradZ_09]

Thanks, I'm not sure what the problem was, everything seems to be fine now.
Engine has had about 5 litres of fuel, so pretty new. Plenty of compression.
But whats the deal with the plug?!
Whats a vapour lock?
Thanks for the help anyway i have no idea why it does that.
PS. OOPS! I had no idea i posted it in the electric forum, POO!! Someone please move it for me?

 

[olds97_lss]

Vapor lock is caused by the fuel becoming a gas instead of a liquid by boiling in the fuel system. In RC, it's usually boiling inside the carb itself. It appears that you have air bubbles in your line, but it's actually the carb boiling the fuel and shoving the vapor up the fuel line. By holding the throttle wide open, then attempting to start it, it forces a lot of fuel into the engine which helps to cool the carb enough to get it running. Once a constant flow of fuel is present (from running), the carb stays cool enough to not boil it anymore.

As soon as the engine stalls, the fuel flow stops and the carb heats up to the temp of the crank case within seconds.

A lot of higher end engines run a composite carb body or some sort of insulator on the carb neck to help with this issue. But, if your running on the rich side, your engine shouldn't get that hot.

 

[BradZ_09]

Ok thanks mate, been out bashin car held up fine, will take plug out later and see if i still running rich