Having trouble with fuel flow!!

Is it perhaps because the needle is open more than you
Expect?
I think the instructions say four turns open but mine is
Six and a half to run correctly.
J

Another thought, are you choking the engine while you turn it over, that is, putting a finger over the air intake and turning it over until you see fuel reach the spraybar?
Tiny engines don't have a great deal of fuel suction , and need a bit of help to get it flowing.

Yes Ivanhoe, I did choke the engine but the fuel did not travel through the tube so I removed the
hose from the engine and the fuel flowed quickly. I then put tube back on carby when fuel was
half an inch away from carby; then I choked engine again, opened needle valve and fuel did flow eventually?
But it doesn`t flow everytime I do this!..perhaps there`s not enough suction like you mentioned?
I open my tee dee 5 turns and it runs (rich) of course!..then I tune it by leaning mixture. I only managed to do
this one time while the engine ran for 50 secs. I couldn`t start the engine again because I`m sure the batt. voltage
was too low because the plug only had a slight orange glow. I checked my batt. with a voltmeter and it read 1.4V.

Mr G

Thats a big tank, the .010 does not have much suction to pull fuel through so the line must be short and the tank at a reasonable height.
But really that tank is a bit large for the .010!

Hi nitroairplane,

Yes the tank is probably a bit too big but I`m only using it to bench test egines.
I have recently shortened the tube and the fuel does flow better. I do have other smaller
airplane tanks but I still don`t know how to set these up? the 2 tanks, one a wedge and
the other a retangular type have 3 pipes and I`m a bit confused?
Could you explain how to set this type of tank up please?

Mr G

coxxoc wrote:Hi nitrairplane,

Yes the tank is probably a bit too big but I`m only using it to bench test egines.
I have recently shortened the tube and the fuel does flow better. I do have other smaller
airplane tanks but I still don`t know how to set these up? the 2 tanks, one a wedge and
the other a retangular type have 3 pipes and I`m a bit confused?
Could you explain how to set this type of tank up please?

Mr G

Don't use the wedge tank on the bench, you're just adding to your problems if you do. Use the rectangular one, set it as close to the engine as you can, then line up the outlet pipe with the spraybar of the engine, I use bits of packing under the tank, adjust it so that outlet and needle/spraybar are on the same level, this is the only rule you need.
The problem you are having sounds to me as if it's caused by that huge tank, with a clunk tank the engine has to suck fuel quite a long way uphill before it even gets to the outlet (Before anyone else jumps in, yes I am aware of head of fuel issues, but I'm being simple here!) and an .010 aint got much suck!
Using a smaller tank should improve matters for you, but don't worry, setting an external tank is not rocket science!
To explain the 3 vents in the tanks, on the wedge tank, the pipe in the corner of the wedge is the supply pipe, the smaller side of the wedge faces to the right of the model when it's used, the top pipe is then the filler, and the bottom one the vent. The pipe in the small end of the rectangular tank is the feed, the other two are normally set together in the top, one is filler (either one) and the other is the vent.
If I haven't made this clear I'll find pictures for you

Wilf

Seems to me if you pull off the line and it flows freely but, when connected it does not then you need to open the NV a little bit more. I open mine up until they draw then close it.

A little trick I do is blow in the vent line until fuel reaches the spraybar. It helps in low vacuum situations. Kinda like a siphon effect.

cribbs74 wrote:
A little trick I do is blow in the vent line until fuel reaches the spraybar. It helps in low vacuum situations. Kinda like a siphon effect.

If you do this remember to put your finger over the other vent or you can get an eye full of fuel, and by 'eck that stings!

I noticed one thing you said, "fuel was half an inch away from carby; then I choked engine again, opened needle valve and fuel did flow eventually..."

If this means, you choked the engine, flipped the prop and then opened the needle, then choking didn't draw fuel because the needle was still closed when you flipped the prop. Sorry if I misunderstood.

I once had an .049 and a wedge tank on a plane and I had to open the NV way more than normal, 6 turns, to get flow, then close it back down to 3 turns before cranking.

Wow, that tank is WAY too big (1oz) and your engine does not have enough power to suck the fuel up the clunk line. The tank is designed for a .049 to 09 size engine.

Cox International wrote:Wow, that tank is WAY too big (1oz) and your engine does not have enough power to suck the fuel up the clunk line. The tank is designed for a .049 to 09 size engine.

If that's the case, coxxoc, raise the tank higher on your test stand and let gravity do the work. Just keep the line pinched when the NV is open and the engine isn't running. And pinch it between flips. That will keep the gravity feed from flooding it.
If you accidentally do flood it, clip the line or close the NV and flip until it fires and burns off the flood.

Think we're getting a little mixed about face here guys, engines don't suck it's atmospheric pressure doing da work.

Hi guys,

thanks for all the advice; I`ve put all notes in my tip book.

Mr G

John Goddard wrote:Think we're getting a little mixed about face here guys, engines don't suck it's atmospheric pressure doing da work.

When the piston travels up the cylinder, it creates a partial vacuum, proportional to its displacement, in the crankcase and pulls air to fill that void in through the venturi. Since the venturi is a constricted orifice the air accelerates creating an even higher negative pressure at the NV orifice to pull fuel in. It seems to me, that sucks.

Thanks Rusty!

Mr G

RknRusty wrote:

John Goddard wrote:Think we're getting a little mixed about face here guys, engines don't suck it's atmospheric pressure doing da work.

When the piston travels up the cylinder, it creates a partial vacuum, proportional to its displacement, in the crankcase and pulls air to fill that void in through the venturi. Since the venturi is a constricted orifice the air accelerates creating an even higher negative pressure at the NV orifice to pull fuel in. It seems to me, that sucks.

Yep, that really sucks.

RknRusty wrote:

John Goddard wrote:Think we're getting a little mixed about face here guys, engines don't suck it's atmospheric pressure doing da work.

When the piston travels up the cylinder, it creates a partial vacuum, proportional to its displacement, in the crankcase and pulls air to fill that void in through the venturi. Since the venturi is a constricted orifice the air accelerates creating an even higher negative pressure at the NV orifice to pull fuel in. It seems to me, that sucks.

That's always been my understanding of the process, and you're right, it sucks!

I was being pedantic guys.
It is actually the 14.7 psi pushing the fluid in
To fill the void.
Sometimes it's easier to understand why plumbing
Tanks works and sometimes not if you think of the
Above.
Brian Winch (the Wizzard of Oz) explains it and much more in
His excellent monthly articles in RCM+E.
If you like engines the cost of the mag is worth it just for
That single article per month.

PS
It is available in the States as (I think) Radio Control Model Flyer
PPS
Coxxoc he's in your part of the world so perhaps writes in an Aussie Mag?

Ivanhoe wrote:

cribbs74 wrote:
A little trick I do is blow in the vent line until fuel reaches the spraybar. It helps in low vacuum situations. Kinda like a siphon effect.

If you do this remember to put your finger over the other vent or you can get an eye full of fuel, and by 'eck that stings!

oy, i hate when that happens i learned that trick from my uncle when i was first getting into fuel power. It deffinetly is not fun to get nitro fuel in the mouth or the eyes

Yes, I love the smell of Nitro but not splashed in the eyes thanks!
And a word on siphoning and blowing fuel through tubes; be careful this type of fuel is toxic!!
We have all placed and removed fuel contaminated lines on and off engines..BEWARE!!! of
putting them in your mouth?

Mr G

coxxoc wrote:Yes, I love the smell of Nitro but not splashed in the eyes thanks!
And a word on siphoning and blowing fuel through tubes; be careful this type of fuel is toxic!!
We have all placed and removed fuel contaminated lines on and off engines..BEWARE!!! of
putting them in your mouth?

Mr G

Yes, it's toxic if you drank a full can, but the sort of amount you can accidentally get in your mouth from these sorts of events won't make you drop dead instantly! It's happened to me no end of times, and I'm still annoying people on this forum!

Mr G is right, my niece is a chemist and she tells me they
will only handle/pour methanol in a fume cupboard.
Makes you think!!!
john

Look I've drunk gallons of the stuff and there's nothing wrong with me

Woof