Exactly, it needs to be open or in auto!
Solved 
!
@Stearmandriver2
I never really followed the routing of the fuel flow until you mentioned it in your reply. By looking at the fuel-flow a bit closer it (of course) makes sense. And by following your suggestions Iām happy to say Iāve got two perfectly running engines again.
It remains a mystery how I managed to start both engines using the wrong configuration. Anyway, Iām glad the problem is solved thanks to your- @FormerSnail5736 and @TheSevenflyer 's help.
Thanks again for your patience and time 
Have a great weekend!
Quick correction: the isolation valve has nothing to do with the fuel flow, but with the bleed air flow.
Like we said before. Just follow a tutorial from EMI and theyāll start. Your procedure is completely wrong. Just look at the diagram on the panel itself and look at your duct pressure gauge to know where bleed air is going.
Like Stearmandriver2 said the air cond panel before start should be Packs off, Bleeds on, Isolation valve Open.
After start it should be APU off, Packs auto, Isolation valve auto, Engine bleeds on, APU bleed off.
New small update out tonight; apparently the update two weeks ago was an earlier internal build that had already been superseded. Hopefully this quashes the āfreezing cockpitā bug that was supposed to be fixed in the last one.
Has the EFB been updated since original release? When it first dropped I had a look and then switched it off as it was distinctly underwhelming.
10 chars
Nothing that I could notice. The next ābigā update will move some setting options that are currently in FMC to EFB. Personally I wanted EFB for Navigraph charts and it works very well.
I was actually pretty happy with the EFB until I went over to the ādark sideā and purchased the Fenix 'Bus. Thatās the standard an EFB in my book. The PMDG product is still better than nothing but Iām blown away by how long it took them to release something this basic.
To be fairā¦ They did pump out 4 variants and worked on the 777 while Fenix did one rework. Not hating on the busbuilders but PMDG getās too much hate on this.
Further, if you saw any of the 777 previews from FSExpo, the tablet in that aircraft has considerably more functionality built into it, and that functionality is intended to be back-ported to the 737 once the 777 is released.
Iām happy with the PMDG tablet because it contains everything I need: T/O Performance calculator for all variants and METAR info. I use my own tablet for Navigraph charts.
Anyone know whatās new/fixed in the 3.0.92 update? Canāt find any changelog on their website.
Read the post I linked above.
Ok. A lot of text to say they released the wrong build with 3.00.0091. So, nothing new was added. Just some mysterious fixes.
If you want to know something, you gotta read.
I did read it. Hence my response.
I saw that, still - how many years has it been since the release of the 73 and we are still in waiting mode for a robust EFB?
Does the Fenix EFB work on Xbox? Nope, their entire aircraft does not.
The folks that complain about PMDG taking a long time to release something completely ignore the fact that PMDG, from the very beginning, built their aircraft for this sim using only native tools, so that they would be available on the marketplace, on PC or Xbox. Obviously if you want to custom build something outside of the sim or using the additional flexibility of the PC ecosystem, youāre going to have a much easier time. Itās not as though there wasnāt a reason PMDG ran into all these obstacles no one else had yet; no one else has brought a complex airliner like the 737 to the Xbox platform.
It kind of makes sense, if you think about it vs comparing PMDG to devs who have not done a comparable thing.
Exactly. Developing outside of MSFS would be easy. The things you can do outside of the sim have no limit but MSFS does not make it easy for developers to do that. This is the step back that MSFS has brought us. Thatās why developers struggle with things like proper weather radars and flight characteristics.