R/C Tech Forums - Hard to restart

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- - Hard to restart (https://www.rctech.net/forum/offroad-nitro-engine-forum/1049782-hard-restart.html)

Is it common to have a hard time re starting a nitro motor after 5 minutes of run time? I haven't ran a nitro in 15+ years. Everytime I roll the truck and it stalls it will not re start even after several different methods.

Fuel tank is 3/4 full, jetting on the rich side to be safe. dont know engine temps as of right now.

Its been years since I’ve run nitro also, but what are you doing when you try and restart it? I’d definitely be checking temps. Have you tried a new glow plug when this happens? Maybe the plug is fouling out due to the rich jetting and possible cool head temps?

I have not tried a new plug yet. I do know if you wait an hour or so it will fire and run again for about 5 minutes. I will check temps soon, I do have a temp gun but haven't found out what temps I should be seeing yet.

Starting it cold I will put my finger over the hole in the pipe to build some pressure then it will fire usually in a few pulls. HOT I generally just stick the glow plug heater on and start doing short rapid strokes on the pull start.

It almost sounds like the engine is running lean and overheating if you have to wait a while before it’ll restart. How do you know it’s running rich? By the smoke coming from the exhaust? Depending on the engine and the adjustments it has, you could be rich on the low speed needle and lean on the high speed or vice versa. What kind of engine? You mentioned a pull start. I’ve been out of the hobby for over a decade, but in my experience in the past, most engines that come with a ready to run aren’t of high quality and are usually difficult to tune and to keep running properly. The quality could have changed now though. Is this a brand new engine? Did you break it in properly?

No it's not brand new that's for sure. I bought it from a local hobby shop's owners brother. It's a HPI 1/8 scale truggy. I dont know just yet what motor is on it. Still trying to even figure out what model it is. I'm definitely a backyard basher and dont need any higher end models. I believe it is running rich due to the sound of the motor & considerable smoke out the exhaust. The smoke cleans up quite a bit at WOT but not completely.

Check to see if the carb is getting hot enough to boil off the fuel and push it back towards the tank.

I would be starting with a cold engine and turn the engine over by hand by turning the flywheel. Turn it over counter clockwise looking at the front of the engine. If it turns over really easily (with glow plug IN and TIGHT), the engine is probably worn out. If this is the case, it will run for 5-10 minutes and quit until it cools off where it will restart again. If the engine turns over with a good snap - hard to turn past TDC, then it’s likely a mixture issue.

Engines that quit are typically too lean or WAY rich. After rolling over however, the engine will consume the fuel in the line while upside down. You will need to re-prime the fuel system (just get fuel to the carb, don’t force any into the engine as you would with a cold engine). Make sure you’re not trying to tune the engine until it’s heat soaked. Run 1 tank through it to heat it up thoroughly.

Make sure you have a good glow plug - use a new one if in question. Medium heat long reach is good - OS #8 plugs are too short. Try a McCoy MC8 or Novarossi C6S. Ensure fuel is fresh or if old, that it was well sealed in storage.

Awesome info!! Thanks I will get to working on that.