Hello - Fuel Problem

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Daniel1960

RC Newbie
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Location
New Zealand
RC Driving Style
Hey guys, great site, lots of info.

Bit of background, Names Daniel for New Zealand, age 19, been a mechanic for the past 5 years. Interested in anything with a motor :p got a fairly modified real life 4x4.

Have recently just got my first nitro rc.

http://www.tiger.com.tw/product/6719-F.html

I'm in the breaking it in process and have come to a halt, runs fine, drive it around for a couple of mins then.... it stops. Can see the fuel going back from the carb to the tank, and it takes ages to prime again.

Have had a search around and have checked the basics: fuel lines, tank seal.

I was wondering if it was at the exhaust end, as the pressure pipe just feed through a hole instead of a fitting like other cars i have seen (pics in above link)

Any help is appreciated, as so far I'm loving the world of nitro RC

Cheers Daniel
 
The break in process can take a bit of time. As it wears in, you're going to have to re-tune it as well. Is it idling well at this point? What are you doing when it cuts out? Are you light on the throttle? Heavy on the throttle? Not on the throttle?

I'm in process of breaking in my Truggy engine as well right now. I went to the track yesterday and my bench tune was WAAAY off from what it needed to be. Took me a good half hour of fiddling before I got it runnable on the track. When I got up towards half throttle of more it would choke itself and flame out. WAY too rich.

I would doubt it's the pressure line, especially if you bought it new....but it's always a possibility. Stranger things have happened.
 
I would doubt it's the pressure line, especially if you bought it new....but it's always a possibility. Stranger things have happened.

It would seem to suggest the back pressure line off the exhaust is blocked. Engine is drawing fuel on it's own effectively and the fuel tank goes negative pressure, engine cuts out and without the engine 'pumping' full with the crank the fuel is pulled back into the tank.

I'd take the pressure line off and check its open on both ends. ie. remove it from the exhaust and check you can blow into the tank and then reconnect the exhaust end and check you can blow in the fuel tank end.
 
Hi

Thank you for your speedy replies,

I have check the pressure lines.
It idles fine, when just driving around, maybe quarter throttle. Doing figure of 8s (or anything ie. big wide circles) it just cuts out, well actually it runs out of fuel. And i can visually see the fuel returning to the tank from the feed line.

There is no fuel or air leaks i can see.

This ones got me stumped.

Once again any help is very appreciated

Cheers Daniel
 
Hey all

A bit of an update, was running the truck before. It did the same thing, still running out of fuel (so to speak). When it does do it, and i leave it alone for 5 mins it self bleeds and fuel is back up at the carb. It has got me really stumped.

Anyone?? :\

Cheers Daniel
 
When the motor stalls, is the fuel boiling in the carb?

Do you have an inferred thermometer? If you do, check the temp at the glowplug, exhaust port, and side of engine block.
 
I was thinking the same as gnarkill. Sounds like your running a bit on the toasty side. Usually, when an engine is silly hot (270F+) and the engine stalls, the fuel in the carb gets a chance to sit long enough to boil in the carb which pushes it up the line.

When it does this, can you put a drop of spit or water on the top of the cooling head to see if it sizzles? (poor mans temp test ;) )

If it sizzles and jumps off, your way too hot and lean. If it just sits there and slowly evaporates, then it must be something else like an air leak at the carb or something.
 
Hey, thanks for the replies.

I've done the poor mans test, and it seem its not overheating.
But now when i start it it revs up, like really revs, on its own. I've checked all my settings and reset them to factory settings.

Does this sound like a air leak, after the carb???

Cheers For all your help.

Daniel.
 
Does sound like an air leak somewhere.

Take a look at this thread, post #6, it will walk you through a pretty thorough sealing process you can do to eliminate an engine air leak as a problem:
https://www.rcnitrotalk.com/forum/showthread.php?t=60832

I do this to all my new (or used) engines before firing them up for the first time just to avoid annoyances.
 
how high from sea level are you? methanol has a lower boiling point than gasoline.
 
Could just be some junk in your fuel/carb?? Have ya tried removing the highspeedneedle and housing, and flush it out with nitro.. Also make sure you dont have debris in your fuel tank/filter..
 
They have it covered, check everything from the fuel tank to the engine and pipe for leaks/blackages. New fuel tubing is sometimes bad, all it takes is a pinhole.
If all that checks out, your carb is vapor locking from the heat as stated above.
 
Hey guys, sorry havent been on for a while, or even lookd at my car, works too busy. Will try all the above :)

Cheers Daniel

ps. I'm in wellington.
 
Slightly off topic, but when my car was running too lean, and thus hot, when it emptied a fuel tank the remaining dregs of fuel were boiling in the exhaust gas heat from the pressure line. Looked like a right nasty place to be that fuel tank!
 
Hey guys, right I've figured its running a bit to hot and boiling the fuel. Can hear it boiling.
So do i have to lean out the hsn or the lsn or both??

Cheers Daniel
 
There is no way for us to know that from here.... a video will show me what is wrong.
best I can tell you is to richen both up close to factory and start over.
First just try richening both needles 1/8th turn and see how it does.
 
some info: methanol boiling point 148 degrees f, flash point 54 degrees f. nitromethane boiling point 217 degrees f, flash point 95 degrees f just for reff.
 
OK smart guy, what about the oil? And what temp do all 3 combined boil at?:p: Just messing with ya'!
250F is when a non insulated aluminum carb starts to vapor lock. That's just from my personal experience.
 
ok scrogg thats above my pay grade. i just barely passed high school.. hay an idea just hit me. even though you are not old enough to remember carburetors on street trucks, heres what i had happened to me.. the fuel line going from the fuel pump to the frame is under suction, if it has even a small leek it will suck air LONG before it will pull fuel. ie ANY pump will pull air LONG be for it will liquid. so this r/c carb might be doing this, if it has suction on the fuel tube. i say replace the tube. and my idea is make it as short as you can.
 
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