Z150 TXRB running poorly

[old gold]

Re: Z150 TXRB running poorly

As I mentioned when I pulled the vacuum hose from the regulator the fuel pressure gauge did not budge. I pulled the regulator and the little screen filter was ~30-40% clogged. (This engine has no shortage of filters!) The regulator also seems to be seized up. Any suggestions to test it further off the engine?
I may replace it at ~170$ and run the engine again before pulling the hp pump.

 

[rodbolt]

Re: Z150 TXRB running poorly

a restricted VST regulator filter will spike medium pressure , however its NOT your issue.
as long as the medium pressure can maintain 50-60 PSI at all RPMs it will work just fine.
40 psi wont work fine.
the HP pump is simply going to step up that pressure from 50-60 PSI to about 725, thats SEVEN HUNDRED TWENTY FIVE psi.
i have personally seen that system run perfect with 80 psi on the medium pressure rail.
that engine can also run without the HP pump but dont try for more than about 1500 RPM or it runs lean.
ALL the VST does is provide the HP pump with a known volume of fuel,VAPOR free and is the return accumulating tank for waste fuel from the HP pump.
it also COOLS the waste fuel from the HP pump to aid in preventing fuel boil.
EFI 2 and 4 strokes ARE sensitive to both over and under pressures more than about 5psi from their design.
the HPDI is NOT one of them unless the HP drops below about500 PSI then it falls on its face.
meaning if the fuel pressure sensor voltage drops below 2.8 or above 3.2 it will show a code, wont react to it and top speed can be reached.
the 725 PSI is also plus or minus about 116 PSI.
above about 850 PSI and it will run rich, below about 500 it starts surging lean and as pressure keeps falling it can and will burn pistons.
there is no alarm nor engine ECU safe mode for low fuel pressure.
see why I am thinking you have HP pump issues?

 

[old gold]

Re: Z150 TXRB running poorly

It sounds like I should stop screwing around and send my HP pump and injectors to Flagship....

 

[rodbolt]

Re: Z150 TXRB running poorly

the injectors wont cause low high pressure rail issues unless they are stuck open.
myself I would start with the medium pressure filter then send off the HP pump.
the injectors are a pain to access and sometimes require cyl head removal to remove them.