Low fuel pressure - is fuel pump the problem?

Hey y'all

I have a 2010 prius with 200k miles.

I recently gave up on P0171 System Too Lean (Bank 1) code and took it into a shop. They're telling me it's because the fuel pressure is low (reading 20 psi when it should be 45) and suggesting replacing the fuel pump. The symptom is a knocking and misfiring that eventually shuts off the engine. Other codes are P0301 and P3190.

I had tried the usual suspects of injectors, coils, spark plugs. And i cleaned out the EGR cooler, valve and pipe.

When I was out of ideas, i also swapped out the fuel pump with an aftermarket one, but after it didn't solve the issue, i swapped it back to OEM.

Based on that, is it reasonable that the fuel pump can go bad like that? Other friends have told me that pumps usually work or don't, and it's unlikely that putting out only half the required pressure could mean something else. So I'm hesitant to believe them (and shell out $850 to just to replace the fuel pump). Could it also be the regulator?

Thanks!

 

I guess it must have been the whole assembly? since i didn't notice them being separate when i did the job, unless i missed something. Looking at those parts the regulator is unfamiliar to me, seems like it must have just been tucked away in the bottom of the pump. I wonder if when i replaced it there was no regulator in the replacement part...

 

Yup, cleaned those when i first noticed issues and that improved things somewhat (used to shut off after 30 seconds now it'll run for up to 2 minutes). Didn't notice anything with the headgasket when i did that, but wasn't really suspicious of it. I guess a bad seal would affect fuel pressure too.

I've decided to take it back in my own hands and play some more. I'll update this thread with what happens.