737 Max 8 Engine(s) Won't Start in Cold Conditions (< approx 6C) Following Checklist

[BragRaindrop933]

ISSUE DESCRIPTION

Description of the issue:

The 737 max 8 engines (especially ENG2) can’t be consistently started from cold and dark in cold conditions < 6-8C. Even when following checklist procedures. I have had some conflicting experiences, where on my very first 737 flight I could start both engines, second flight I could start neither, but most consistently in recent attempts ENG1 will start up fine but ENG2 will refuse to start up.

This has looked random, but has been proven by trial and error to be linked to colder air temperatures <6-8C. If ambient air temp is above 8C then both engines start every time. If ambient temp is approx 6C then ENG1 will start but ENG2 won’t. At temps <6C then both engines will fail to start.
See post below.

737 Max 8 Engine(s) Won't Start in Cold Conditions (< approx 6C) Following Checklist

You are both onto something @DrVenkman3876 & @CommonBloom31 . I’ve just quickly tried 4 cold and dark starts at various locations and when Air temp is 8C or higher ENG2 (right side) starts. When Air temp is 2C neither engine starts. In between those temps left side ENG1 engine starts and right side ENG2 doesn’t. This definitely ties in with that switching live weather off thing. There’s been a good few colder mornings here in UK and most of my 737 flights have been originating locally where …

Did you experience this issue before you joined the Beta?

No, the startup on the 737 max was always consistent for both engines in FS2024 in original release as well as SU1.

If applicable, which aircraft is experiencing this issue:

Asobo 737 Max 8

[PC Only] Did you remove all your community mods/add-ons? If yes, are you still experiencing the issue?

YES

FREQUENCY OF ISSUE

How often does this occur for you (Example: Just once, every time on sim load, intermittently)?

Just about every time (see inconsistent reference in first paragraph). ENG2 will not start. Neither ENG1 or ENG2 will start below outside air temp of 6C

REPRODUCTION STEPS

Please list clear steps you took in order to help our test team reproduce the same issue:

1. Enter 737 cabin cold and dark with weather set to < 6C
2. Follow checklist until ENG 2 start
3. See if ENG2 will start (it doesn’t for me) N2 @25% then Fuel cutoff to idle does not start engine.
4. Try ENG1 start which will not start when ambient temp is <6C

YOUR SETTINGS

If the issue still occurs with no mods and add-ons, please continue to report your issue. If not, please move this post to the User Support Hub.

What peripherals are you using, if relevant:

TM Hotas One & Pedals

[PC Only] Are you using Developer Mode or have you made any changes to it?

NO

[PC Only] What GPU (Graphics Card) do you use?

3090

[PC Only] What other relevant PC specs can you share?
5950/3090/54GB/WIN11(24H2)

MEDIA

Please add a screenshot or video of the issue occurring.

[END OF FIRST USER REPORT]

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Do you have the same issue if you follow the OP’s steps to reproduce it?
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[Sleevezipper]

Do you have the same issue if you follow the OP’s steps to reproduce it?
• Yes, but also somewhat inconsistent. Today I started from EDDK, the left engine started just fine but the right engine didn’t want to start after the introduction of fuel. I tried to repair and refuel the aircraft but that didn’t help either. Yesterday I was able to start both engines.

Provide extra information to complete the original description of the issue:
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If relevant, provide additional screenshots/video:
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[Fadros6669]

Just happened to me to. Restart 3 times the Sim and ENG2 wont come on everytime.

[BragRaindrop933]

I’ve been playing around with it a bit and it’s too early to diagnose, but it seems to relate to the two ELEC1 and ELEC2 HYDRAULIC SWITCH positions. I played around with them and got both engines to start. I need to try to refine what I’ve found though.

[Nikita]

Perhaps you have already tried this, what happens if you start the right engine first? As I recall, the APU Bleed should be On and the Isolation Valve should be Open. Not in the sim right now.

[BragRaindrop933]

I always have APU bleed on the engines don’t start without it. I also always have the Isolation valve set to ‘Open’.

The starting issues are manifesting I feel in the hydraulic ELEC1 and ELEC2 switches. Before SU2 I never used to turn these on until after engine start, but if you go by the checklist it says to turn ELEC1 Hydraulic switch ON before start. (which is new to me). See first line in the checklist in the screengrab. (ps. don’t go by the position of any other switches in this screengrab as I only opened this up to show you the relevant EFB checklist section.)

[Nikita]

Sounds like you may have this sorted out.

Here is my procedure flow from the PMDG 737s. I bolded a few items to confirm yours…

DEPARTURE (B737/738)

• Cntl 6: Wing fuel pumps ON
• APU Start, SET Cruise ALT
• Briefing Preview/Charts set
• APU Gen ON, APU Bleed ON
• Electric Hydraulic Pumps ON
• Cntl 2: GND PWR, JETWAY REL
• PUSHBACK, CHOCKS, TUG
• STYLE, DIRECTION, DEG
• START, LEGS, PROG
• MFD: ENG
• Release [Park brake]
• Cntl 0: GRD, fuel at 25% N2
• Air Gens ON, APU OFF
• APU Bleed OFF, PACS Auto
• APU Isolation valve AUTO
• [Park brake] [Park brake]
• [Anti-collision lights] ON
• Autobrake RTO, Flaps 5 SET
• MFD SYS, Flight controls
• [Taxi lights] ON

[BragRaindrop933]

I’m now back to Left ENG starts no problem but the right ENG won’t. I’m doing nothing different from earlier. Tried various combinations for ELEC1 and ELEC2 Hydraulic switches. Nothing works one ENG2 decides not to start. N2 climbs to 24.4% and adding fuel does nothing. It just sits there forever on 24.4%. Seems like a bug but an inconsistent one. Also continually getting an ELEC warning on the front panel. Which also ties in with the electrical blackout were seeing at cruise. Maybe it affects engine startup too. Who knows. I’ll keep plugging away for clues.

[Nikita]

I really have to get into the Max and give it another try, but life is in the way today.

If you have not already, try starting the Right engine first. That is SOP in the NG 737s and possibly the same in the MAX. Both Electric Hydraulic pumps go on in the NG after the APU is running, did this change in the MAX?

About that electric bug, I was going to suggest that you pull a “Sully” and leave the APU running and on the bus in-flight to see if that proves the defect case; but it appears you and others already proved that with leaving the GND PWR switch open as a work around. Will have to look at that tomorrow or over the weekend to see if I can confirm the bug report you folks reported.

[BragRaindrop933]

The only reason I started the left engine just now first is because the right engine wouldn’t start. So I tried the left and it starts fine. But the right still won’t start.

Earlier tonight I got them both to start fine for a flight, just doing the same thing as I am doing now. So all I can deduce right now is there is a bugged state that can effect the engines starting up. Mostly right hand one, but sometimes both. But not every time, which is what makes it weird.

[Nikita]

Morning, well I’m sitting here in the MAX at KPHL (default) with the APU running and Engine 2 start stalled at 23.6% N2. For some reason the N2 doesn’t come up to 25% and the sim won’t continue the start sequence upon the introduction of fuel. I’ve tried waiting for 25% N2 and also introducing fuel sooner, which should not matter as Boeing has a bit of automation here to make sure fuel is not introduced too early, causing a hot start. This is a defect. The question is, is it a defect in the checklist (unlikely) or a defect in the bleed air management or other start sequence simulation. Would be great if some other pilots could confirm this right engine start defect so we can get this one bug logged.

[BragRaindrop933]

@Nikita

I’ve tried waiting for 25% N2

As you say N2 never reaches 25%. 24.4% was the highest I saw. It doesn’t start by using their checklist either. I just don’t know why sometimes it starts fine. Definitely some bugged state going on. Sometimes it’s both engines that refuse to start. So all in all it’s a bit of a mystery.

[Nikita]

If you know anyone else who has been flying the Max before SU2, maybe reach out to them to see if they can get #2 started? Good to have others eyes on something like this.

[BragRaindrop933]

@DrVenkman3876 Are you stable enough with SU2 to run your eyes over the Max for this RH engine start? Right engine is frequently not starting. Lots of bugs fixed, but new ones introduced. This startup thing is weird, and currently no workaround.

[DrVenkman3876]

I am plenty stable in terms of not crashing - removing FSLTL models from my Community folder cured my CTD problems. Not in the sim right now to test, but it does sound like there’s an issue with engine startup.

[Naomi9093b]

Do you have the same issue if you follow the OP’s steps to reproduce it?
•

Provide extra information to complete the original description of the issue:
•

I have the same problem, except engine 1 won’t start. AND when I have the sim load with the engines started, engine 1 parameters are way different than engine 2.

[Chewwy94]

It looks as if your packs may still be in the AUTO position and not OFF, which they would need to be for engine start, alongside your Engine 1+2 and APU Bleed being in the OFF position also.

[BragRaindrop933]

Thank you, but that image isn’t a good example I was just posting it to show the EFB checklist. I really should have cropped it. I wasn’t in the process of starting it up there, just showing what the checklist said. The switches in that image are all deafult as per when you load into aircraft and flip the battery switch.

@BragRaindrop933

(ps. don’t go by the position of any other switches in this screengrab as I only opened this up to show you the relevant EFB checklist section.)

[Chewwy94]

Apologies for my mistake there, I can see that now :)!

[Fadros6669]

Did another try this morning and still can’t fly the 737 max, Engine 2 isnt starting past 23 23.6