CalCBR

Hey guys,

First off I'm Cal, from Queensland AU. I do apologise that my first post is a noob "car won't start" thread, but there you go.

So, I have done a search but didn't come up with too much information. If there's somewhere that covers this topic well please link it and I'll have a read through it to save you retyping and such.

I can't tell you too much about the car's details because I don't know a lot about RC cars and I actually got this one as a gift. Score.
I do know that it is a Chinese branded one.

I have had it running before, but not for long. It got quite hot (melted the plastic cover) and conked out. Nothing was seized or blown, but the car wouldn't restart. I left it sit for a fair while but I've had more time now so I've been playing about with it.
There is discolouration on the (>technical term missing<) part that joins the engine to the gears that turn the driving gears. So the part with discolouration is joined to the engine.

I seem to be having fuel flow issues. Reading some things I found online and on this forum I've done the following:
Checked glow plug (works, and is a new one anyway; I do have a spare)
Cleaned carb and set to factory (no blockages)
Checked fuel lines (all fine)
Blown through the pressure line attached to the exhaust (pushes fuel through the fuel line when detached from the carb, but doesn't when the fuel line is attached to the carb)
Used the pull start with my finger over the exhaust (this pulls fuel through the system and did give a bark of life but it didn't continue so I'm assuming the fuel isn't flowing under the vacuum of the engine alone)
Checked the exhaust gasket (the gasket between the two halves is fine, the rubber that joins the exhaust to the manifold (correct term for an RC?) is fine, inside the exhaust however there was nothing (struck me as odd, but again I don't know much about RC cars) other than a metal plate with several holes that I assume is a baffle of sorts to help back pressure and noise)

I will mention I did have the cylinder head off (the part the glow plug screws into and is finned to dissipate heat; in case I've got the wrong term); but I screwed it back down as I would on a normal engine, tensioning the bolts quarter turn at a time in diagonal opposites, to ensure a good seal.
Is there a way to check compression on these little cars?
I can feel compression if I put my finger over the plug hole (with the plug out) and I can tell there's compression with my finger over the exhaust; but I don't think there is enough.

Anyway, that's all the information I can think of for now but if I've left something out please let me know and let me know how I can get the information (as I said I don't know much about RCs).

Thanks in advance for any help you guys can give, and again I apologise my first post is a problem one.

scary_jerry

That's a pretty impressive list of 'checklist items and procedure' for a 'nitro noob'.

I'm picturing that the 'meltdown' started as the fuel setting kept getting 'leaned' (fuel supply/lube) got decreased by closing the needle valves.

I would 'pull glowplug.......cover plug hole with rag just to keep from getting fuel in the face.....Open fuel needles about a turn (counterclockwise)-crank motor over a few times....hopefully getting some fuel/lube into the engine-install glowplug and with a fully charged/fresh battery glow igniter get it to come to life'. It sounded like no fuel was being drawn into engine because needle valves were closed too far and that will cause excess heat during running. If the 'meldown temperature' has happened you would be able to turn the engine over very easily by hand with the glowplug installed when it should actually give you that little 'bump' off top dead center when it should be providing the 'bang'. (the 'OTHER meltdown' is .......SEIZED........)

I found a very 'tight window' for the tune on my son's 'Chinese 1/10th scale nitro car'. So to get it going you have to get an indication that it's got a drop or so of fuel in the combustion chamber and the 'glow' on the plug and some 'squeeze' for that 'nitro moment'......

Geezatec

Recheck your GP & Igniter. Is it wet with Fuel? Color of GP w/ Igniter orange or yellow? If orange replace Battery. If using alkaline, use fresh ones, if rechargeable, charge the up 24hrs before retrying.

CalCBR

Thanks for the replies guys!

Heh, I am a nitro noob, but I've got a couple years of mechanic experience. Same thing, just this is smaller.

I thought the same thing with regard to the overheat being from a lean mixture.

I do get a nice bit of resistance when cranking so I'm happy that the chamber is mostly ok.
If I crank the car with the air filter off, plug in and my finger over the exhaust I get fuel squirting out of the carb but I don't know if that's getting through to the chamber.
If I try the same with the air filter on and plug out and get fuel coming to the cylinder that would solve that mystery I suppose; but if I need my finger over the exhaust to do so does this indicate a vacuum leak?

The old glow plug was wet and quite a nice darker colour; what I would call rich actually.
I recharged the igniter fully before trying this most recent time, and I also checked it with the plug out of the car and got a nice bright, strong glow.

Although I believe they are fine should I be checking the batteries in the car as well? Starting the car is separate from the car's electrical transmitter yes?

blis

Mix should be very light mist, not wet fuel!
Sound like your idle mix is rich... Reduce the IDLE and chase with LSN needle until you cet an idle without using throttle. It's going to richen and stall after 4-5 seconds for a good tune, so heat it up with hair dryer as well. Once it's firing and idling (4-5sec) then tune up the HSN TOP NEEDLE so you can throttle the car without it leaning out and top revving. Then set it down and drive around till it warms up and then set top needle till she's blowing a very light trail of at TOP WOT.

• Set Carby Idle gap to a maximum of 1mm
• Check and set SERVOS and throttle return so carby is closed to idle gap.
• Ensure all fuel and pressure hoses dont leak
• Check plug and glow starter
• Check flywheel and clutch, ensuring it's not engaged
• Richen the Top needle 1 turn to ensure fuel pressure (dont throttle)

1) Remove plug and crank engine until there's no chance of flooding
2) Replace plug and attempt to start

3a) If it seems to fire at the first pull and richens - LEAN CLOCKWISE 1/4 TURN the BOTTOM NEEDLE (LSN) and go back to Step 1).

3b) If it doesnt start at all, block the exhaust stinger and build up fuel pressure and still no luck - RICHEN ANTI-CLOCKWISE 1/4 TURN the LSN. Go Back to Step 1).

3c) If nothing still works, remove the fuel pressure line from the exhaust manifold and blow some pressure down the fuel line, you'll hear the fuel squirt into carby. If there's fuel, you've just flooded your engine, Give it 1/4 turn more IDLE and LEAN the LSN 1/4 TURN, and go BACK TO STEP 1).

There's always a chance the engine isnt run in, or it's so shagged it wont start, but in my experience one can always get a COLD Nitro engine started unless it's not broken in, so if the engine is tight, it needs heat, if there's no compression, it will fire cold and will likely flame out when it gets to full operating temps.

Good luck.

Geezatec

Put 3 drop in carb, and try starting. If it starts a second, you have enough compression, if it starts than dies, no fuel entering the carb. Your carb air gap maybe to wide. 1.5 or over. 1mm would be fine. Elimentery science class, of vacuum and siphoning. Knowing how to prime the engine.