SX225TXRZ - Low fuel pressure

[mesias_yam]

Today I tried cranking the motor after the ring job... of course it didn't start. It turned fine with the starter and even had a few combustion cycles but it died. The fuel rail read around 14-16 psi with the switch ON but I can't hear the HP fuel pump. I think that pressure is from the LP pumps after priming the lines with fresh 50:1 premixed non-ethanol fuel.

This is what I've inspected so far:
1) No leaks, fuel rail is at 14-16 PSI
2) 30A fuse is good
3) With key ON I read 14v in HP pump red terminal
4) With key OFF, HP pump blue terminal reads 8-9v when the key is turned ON and it drops to 0.44v. After 4 seconds it goes back to 12v.

No change in PSI during this test. Do all this mean the pump got fried?

[rodbolt17]

can you hear it run? the fact it has anything means it must have run some.
voltage looks good.
take it apart soak the pump in seafoam or combustion chamber cleaner,clean the VST filter and try again.
it is rather hard to believe someone would actually do a set of rings and not the fuel and cooling system at the same time.

[mesias_yam]

No, I can't hear it... but some pressure is build definitely. I shouldn't chase anything at the main relay and/or ECU, right?
The main reason to dissemble the motor was to check cooling passages. I had to do some scraping to the heads but it wasn't that bad thanks to recently flushing the power head. More details can be read in the link below.
I also cleaned the VST tank and filter recently (maybe a year or two ago) together with cleaning the injectors. LP pumps are also new, OEM. What else can I do to ensure proper performance?
I'll get the HP pump soaked and cleaned again, not a biggie...

[rodbolt17]

try soaking it then hitting it briefly with 12V with jumper leads.
you can reverse the polarity briefly to aid in knocking it loose.

[mesias_yam]

The pump turns... I left it soaking in Seafoam and it turns... it's just not building pressure. I hooked a hose to the outlet while submerged in Seafoam and if blocked there is no pressure. Is this expected?

[99yam40]

are you sure it was turning the right direction?

[mesias_yam]

I switched polarity to tested it... there is flow both ways but not enough pressure. As soon as i received the new o-rings I'll install it to confirm. I don't have much hope on it...

[99yam40]

I have no idea what kind of impeller that pump has, but if the screen filter is not plugged up then the impeller must be toast

[mesias_yam]

But it gets toasted out of what?

[99yam40]

if it is run dry it could melt it maybe if melt-able.
come loose from shaft(if possible).
did you pull the screen when you tried it?
and if pulled did you look up inside to see if it was plugged somehow?

these are just wild guesses

[mesias_yam]

The pump did not run dry, I primed the lines and the VST with 50:1 mixture from a temporary container. I tried the pump by itself, no screen... no visible blockage. By now I'm convinced I need to replace it but I want to make sure there is no hidden issue causing the failure.

[99yam40]

Maybe Rodbolt will chime in if he has ever seen a pump run before but not put out any pressure.

Boscoe probably has cut one open before ,so he may know what the pump is made of and how this kind of failure is possible

[mesias_yam]

I can only see that happening if the pump runs in fluids of different consistency... Seafoam is pretty similar to fuel.

[mesias_yam]

Are you guys familiar with any Walbro pump that fit this model?

[rodbolt17]

yes I have cut open those pumps.
they do not put out much pressure when free flowing. they have no internal regulator.
the pump can become uncoupled from the pump motor.