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Guest Dkoy

Engine starts even with fuel cut off?

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HiJust a little problem, - I have been living with since I went to FS9 I guess. When I start the engines - they start to run at 20% N1 even if the fuel levers is in cut off position.I am sure I have seen this with some other add on aircrafts - but yesterday I noticed it again with the PMDG737.Any idea why this is happening?BrSteen

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Yup!!! This is due to "gravity suck" from wing tanks...

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You're mixing some things up...I believe you are referring to "Gravity Feed", which enables the engines to be porvided with fuel from the wing tanks even without any fuel pumps operating.For the engine to work, you need to have the Cutoff lever in the Run position, otherwise the fuel can't reach the engine.If you were able to start the engine with the fuel levers in the cutoff position (and electrical power was available) then I'd say that's definitely a bug, and a serious one at that.Regards,Mark

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i think he was perhaps referring to the fuel pump switches.and if you are having the levers in IDLE position you can start the engines with no fuel pumps on.Otherwise all i could think about is that you think the engine is runnning if the N2 is reaching 20, this is not true at allthe only thing hapening at that time is air compression due to the startermotor but no fuel injection and no combustion either...but the air is being compressed and decompressed, that's true yet the engine itself is not 'running'Cheers

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There is a psuedo-BUG in the product that I mentioned in another post.The flight sim fuel logic DOES follow the default CTRL-SHIFT "mixture/jet fuel" commands.The PMDG Start Levers do NOT follow those commands.So, it's possible for your engine start LEVERS (on the pedestal) to appear to be in CUTOFF and still have your engines start.How can you tell what position your fuel valves are in? The lights on the overhead seem to work pretty well. If they're dark, your valves are open. When they're lit, your valves are closed.One caveat, though... When you hit CTRL-SHIFT-F1, your engines WILL die (because you just issued the FS command to cut the fuel), but the Engine Start Levers will not move and the valve lights will not light.I cover this in the new tutorial... for maximum realism, when you're preflighting the aircraft, in the first few steps bring up the throttle pedestal, and move the start levers from cutoff to idle and back again. Then you're sure that you've shut things off. But don't touch the mixture control on your yoke if you've got one!

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No I don't mean the fuelpumps - unfortunately. It is the start levers. I just did a test again. APU on, bleed air, and then the start switch to GND. At 20% N1 - the engines starts running with the start levers in cut off.See the screenshot here.BrSteen

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>No I don't mean the fuelpumps - unfortunately. It is the>start levers. I just did a test again. APU on, bleed air, and>then the start switch to GND. At 20% N1 - the engines starts>running with the start levers in cut off.>>See the screenshot here.>>Br>Steendid you read my previous post? move the start levers to run, then back to cutoff. Make sure the valve lights on the overhead are lit (signifying that the fuel should be cut off).Try and start now, by placing the start SWITCH in GRD.

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You were right. I just loaded the 737 and the valve lights are out. Then I moved the start levers to on - then off, and the light were lit.But what is the reason that they are "out of sync" when I load the aircraft? It has never been like this before, and if it is not happening at all PMDG737 users there must be something to do?BrSteen

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"Otherwise all i could think about is that you think the engine is runnning if the N2 is reaching 20, this is not true at allthe only thing hapening at that time is air compression due to the startermotor but no fuel injection and no combustion either..."Lenny... The normal idle rpm of a 737 engine is about 20% N1, (N2=59%). A pneumatically-driven starter motor cannot spin the engine this fast.There are other parameters you could use to check to see if the engine was actually running (and not just powered by the starter motor). E.g. EGT and Fuel Flow. Fuel flow should be about 600lbs/hr (272Kg/hr), although I believe the values in PMDG were modified to allow normal taxy in MFSF (due to the "sticky" runways).Hope this helps.Cheers.Ian.

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I believe it IS happening to everyone, and they either don't notice it and leave the levers in cutoff for the duration of the flight, (like I used to do before I discovered this) or they flip the levers to idle, then back to cutoff as part of cockpit prep, which is what I do now, and what Tim recommends in his tutorial and post above.I like to cycle the levers so that the valve lights come on. I like the visual feedback that I've got things set up right during preflight.Whether or not it's a bug in the plane, I don't know. I suppose PMDG could add code to the aircraft startup routine to check the state of the valves as far as MSFS is concerned, and set the lever position and light state accordingly, but perhaps that's not possible due to an MSFS limitation, or something. Dunno.

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