Car wont start when engine is hot

[GTI@UAE]

Hello everyone

I own a 2006 mk5 gti that is modified. I've been having this issue lately of my car not starting after it has warmed up. I can drive around for as long as I want with no issues but as soon as I turn the engine off it won't start. The first attempt of trying to turn the car when it's hot it would turn on, idle for about 2 seconds and then stall and then all other attempts after that it will just crank without turning on. The only way it would start when its hot is when i remove the g410 sensor. PLEASE HELP!

Things I ve changed:
G410 sensor
Starter motor
Camshaft sensor
Crankshaft sensor
Hpfp
Coolant temp sensor (only one that's next to vacuum pump, will replace the one under the intake manifold today)

Mods on the car:
Gtx3076r with 44mm external wastegate controlled by gfb3
Forge dv
Aem wideband
Rs4 injectors
APR hpfp
Walbro 525 controlled by pm4 (will be going back to stock today aswell to see if that's the problem)
Recently installed 165 fprv and 200 bar fuel sensor because car was running out of fuel with the rs4 fprv (done a few reflashes with the new setup, on the third this started happening)

Only code I have is "low fuel level"

My tuner thinks it's the pm4 acting up, contacted torqbyte they say it seems to be OK After I sent them a screenshot

Has anyone come across the same problem I'm currently facing and what fixed it for you. Really appreciate some support.

 

[GTI@UAE]

I've also changed the relay in the engine compartment a d checked the fuse on the side of the drivers side. But can someone please let me know if we have a relay under the dashboard drivers side for the gtis?

 

[GTI@UAE]

Just solved the issue today, it was my lpfp 535 walbro. What are the odds of a brand new 535 walbro with probably less than 200 kms failing! Been trying to tackle this issue for a bit of time now because never crossed my mind a new pump would fail especially that I was running twin 450 walbro for over 4 years in another car.

But to be honest I still don't understand the relationship between unplugging the g410 that made the car turn on! If the pump has failed (when it overheats) then how does it pump fuel when I disconnect the g410 sensor.

 

[ROH ECHT]

I have begun to believe that LPFPs in our MK5s can be tricky. After my TTRS failed, I tried two other pumps in the OE basket paired with the PM3, and they wouldn't work. They tested OK to run at 12v....but I think some do not play well with the control module/unit. I could drive mine under light throttle...but at full throttle it would choke and LPFP pressure would drop to 1.2 bar with those two new pumps. I suggest just using what has previously worked for you, or for another who's words you trust.

As far as it running when the G410 is unplugged....the sensor allows the ECU to moderate the pressure. Same goes for the rail pressure sensor (G247). So, it being unplugged forces the ECU to run the LPFP at a constant pre-set load. The tank return valve, built into the filter, should protect the system.

As far as the control module goes...I recommend try using your OE module with your next pump. See if it works before reconnecting your PM4 if you find it necessary to do so.

Sorry I don't have anything more conclusive than my thoughts on it all. Have you tried MK5GOLFGTI.co.uk forum? There may be more who've tried LPFP upgrades and are still active. https://www.mk5golfgti.co.uk/forum/index.php/board,3.0.html