MDS 40 engine Runs cuts out when plane is vertical

by Brian
(San Antonio,Tx)

My MDS40 engine runs great at idle and on the ground when the airplane is straight and level. But when I take the airplane and tilt it 90 degrees the engine cuts off...

Like I said, the engine is a MDS 40 glow engine. It's about 2 yrs old and I'm currently running 15% nitro glow fuel. I was told that 10% nitro was good for breaking in the engine. But once the engine has broke in use 15-20%...

Any Ideas...

Just got into this hobby and have not had much luck with tuning this engine.

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MDS 40 engine Runs cuts out when plane is vertical

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90 degree Engine Stalls
by: Tehachapircflyer

Ok you state the the engine stalls at 90 Degrees. Well there are two 90 degree Directions. Is this with the engine facing the ground? Or facing the Sky?

If facing the ground then it would be the pickup in the tank is not falling forward and starving for fuel. And if facing the sky well then there isn't enough pressure to push the fuel upward against gravity to the carberator sounds like your tank may be the issue not the engine.

Make sure your tank is sealed with no leaks. The muffler pressurizes the tank and feeds the engine. On the ground it runs fine doesn't need as much pressure to push fuel to the carb.

Just my thoughts may be it is the engine but I'm thinking not. If it is then it would be a port timing issue and I wont even go into that.

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Vertical starving of fuel
by: Bill

In addition to all the good advice you received there is the possibility that the clunk has fallen forward and not falling back when you go vertical. Can you see the tank if you hold the plane in your hand as you tilt the plane horizontally and vertically?

Actually, the clunk line should not fold in on itself, it should have enough stiffness to stay in the fuel at all angles and yet flexible enough to stay where the fuel is. The length of the clunk line should be just short of the back of the tank when the plane is level.

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Figured out problem BUTTTT....
by: Anonymous

the issue was the needle valve seal, replaced it and engine ran PERFECT!!

Not even 4 min into this flight after rolls spins hammerheads the wings folded in at about 600ft so all I could do at that point was watch the plane crash down motor first, still has good compression spins well but broke the plastic that holds the needle valve on to the engine...

:/ oh well at least we figured out what the problem was in the event someone else has this issue...

what we did to fix it was cut a small 2mm size of fuel line and fit it over the needle valve and screw it back on...

the fuel would cut out if pointed vertical into the sky ran perfect when pointed down to ground...

checked fuel lines in the tank and all was well.. but this seemed to fix it and it ran flawless for 4-5min with no cut outs...

Thanks for the help, well try to get this put into another plane this week and give it another try in hopes nothing is damaged inside the motor, wont know that till later today when I can open it up and check parts...

Thanks again!!

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aww man...
by: Matt

Glad to hear you figured out the problem with the engine.

Sorry to hear about your plane. But look the bright side, you are getting a new plane!

That's always what makes me feel better after a crash... Buying a new one!

Good luck to you, let us know how it goes...

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MDS 40 engine Runs cuts out when plane is vertical
by: diego

Hi! I have the exactly same problem when pointing my plane up, the engine dies after like a couple of seconds. what I realized is that some fuel drips out from the needle valve! maybe that's the problem but I don't know how to fix it! I've checked the fuel line into the tank and it's working perfect!

can you explain me more detailed about fixing it with the fuel line as a sealer??

I really aprecciate your help in advance!!

Good flights!!

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Return to sender
by: Anonymous

Totally non technical solution:
I had the self same problem... I took the engine back to the shop and next thing I knew a brand new engine arrived through the post, without the problem.
Viva consumer rights!!!!

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Possible lean condition, or...
by: I_FLY_LOW

If the plane was in a hard landing, in a previous flight, where it nosed over, the clunk in the tank may have been shoved to the front of the tank, it'l run out of fuel in a nose high attitude, otherwise, it's set too lean.

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Minimizing damage
by: Anonymous

You claimed that after the wing folded there was nothing you could do. Sometimes you are right but many times it is possible to greatly reduce damage.

Once, after folding a wing, I inputed full up and full rudder and the model went into a spin. Another time I broke the wing hold down and the entire wing came off.

I was able to hold full rudder and that caused the fuselage to come down at an angle, instead of straight in. This greatly reduced the damage, but it would have been less if I had held right rudder instead of left. By holding left it caused the fuselage to hit on the right side and the tuned pipe (oh well).

In both cases the model was repaired and flew again. NEVER GIVE UP!!!!

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