Help diagnosing no start

[elrobolobo]

So here is the basic of what is happening so far:
I imported a car NZ->US and it arrived about three months ago, it ended up waiting about 9 months to be exported because Covid yada yada.

Car arrives, runs great but doesn't pass emissions and needs a new battery and radiator. Turns out a new fuel pump helps it pass emissions, but quickly dies again, so I wire fuel pump directly from battery and get a new upgraded walbro 255. 
 

Car is good for about a month, then on my moms birthday it starts being sputtery, and I ignoring long enough to finish out the day, but by the end of the day its pretty bad and the next day it turns over but doesn't start. 

I change out the spark plugs and fuel filter, confirm each plug is getting spark, and fuel is being delivered at 50psi on start up, check all fuses, they're fine. I do a comp test (even though it is below freezing on a cold engine and get between 85 and 90psi on every cylinder. I even disconnect the cat just to make sure its not that being clogged that is the problem. The tank has enough fuel to fully submerge the pump, I set the timing back when I was doing emissions, and the CAS to make sure it wasn't broken. AFM is getting 12v.

Is there any thing else I could do to make it run before taking it to a shop? Trying to check all the cheaper solutions before having to think about a rebuild.

Edited January 27, 2023 by elrobolobo

[GTSBoy]

If real (ie an accurate measurement, not from a faulty gauge) then 50 psi is too high. 43psi key on, not running, is correct.

[elrobolobo]

Would 7 psi off be enough to make it entirely not run though? 

[GTSBoy]

No, it would just be pig rich. But.... if perchance the fuel pressure reg is not working at all and it's still delivering 50 psi once there is some vacuum (when it should drop to 30something psi at idle) then it could be too rich to want to keep running.

So, identifying a possible problem with the measurement of the pressure is the first step towards seeing whether there is actually a problem with pressure. Faulty instruments are often worse than no instrument.