STFT Suddenly way high - possible causes??

[sci85]

Hey all. Like a lot of folks here, I'm learning things as I go. I've had my Gen 3 LS for a couple years now that was tuned by a knowledgeable tuner awhile ago. It's run pretty decent over that time. The other day however, I noticed on startup it was taking a lot longer than usual to fire so I knew something was not right. Went our for a run with the scanner hooked up and immediately noticed the STFT's were stupid high. 50%+! Wouldn't take throttle over 3k rom either. I nursed her home and now scratching my head as to what's going on. I'm running a 5.3, P01 ECM, TSP Torquer 2 cam, headers, O2 sensors in the collector, Walbro 255 pump, OEM injectors, Corvette regulator, MAF tune. I don't have a fuel pressure gauge so I can't tell at this point if I'm having pressure issues.

Just Looking for some ideas or tests on how I can narrow down the problem. Thanks!
C3CorvetteCurrentTune.hptRun3_3KrpmIssue.hpl

[blindsquirrel]

Not having a fuel pressure gauge while trying to diagnose a fuel supply issue is like trying to pull a cylinder head without any sockets. Not everything can be fixed or diagnosed by looking at a screen.

[sci85]

Not having a fuel pressure gauge while trying to diagnose a fuel supply issue is like trying to pull a cylinder head without any sockets. Not everything can be fixed or diagnosed by looking at a screen.

No doubt. And that's next on my list but before I go down that route I just want to make sure it's a likely cause. Would loss of fuel pressure or flow create a lean condition like this? Would it normally make the engine run rough or have other symptoms? I did notice when I removed the cap from the schrader valve I could hear it gurgling so maybe that valve is bad too. Thanks.

[blindsquirrel]

With EFI, where amount of fuel delivered is a direct result of pressure supplied to the injector? Of course.

[sci85]

With EFI, where amount of fuel delivered is a direct result of pressure supplied to the injector? Of course.

Yeah I guess that was kind of a stupid question. Thanks for the reply nonetheless. I'll get a gauge and make sure pressure is good then move on from there. Thanks.

[sci85]

Slapped a tester on her. Yep, 29psi ain?t gonna get it done. Appreciate the reply?s.

[blindsquirrel]

If the cause is a clogged filter, it's likely what's plugging it up is brush material from a dying fuel pump. That's the nasty black crap you see when you blow out an old filter... when you see that, it's time for a new fuel pump too, not just a filter.

[sci85]

Yeah will start with the filter/regulator and go from there. Thanks again.