no way that pressure would drop to 5-12 while running that would be a stall condition.

alldata shows koeo pressure should be 50-57psi

does not give a specification during koer

reading the trouble diagnosis for fuel system it says that if pressure increases over 57psi during koeo(ff) then it is either a restriction in the fuel return pipe or replace the fuel pressure regulator. says to verify that the o-ring seal is not damaged before replacing the regulator.

 

Appreciate the fast response.

Maybe I'm remembering the numbers incorrectly, but that's about what my "High Quality" manual at home stated. Like I said, I am probably off on what it stated for pressure drop.

Nothing fuel system wise has ever been touched (outside of filter changes). I'll see if I can blow some compressed air through the line to eliminate/locate the restriction possibility- I have 186k on the stock FPR- I've gotten my money's worth out of it if it's time to part ways.

 

sounds good yeah i would definitely make sure no kinked lines or junk in the line first if it flows fine then check that seal by that point you might as well replace it anyhow so id go ahead and have that on hand.

 

I bg44k'd the fuel system not too long ago so unless there's a kink i think it will be the fpr.

hopefully picking up a TPIS AFPR from an LT1 before the weekend. less than half the price of the stock replacement here in town.

 

Was able to pick up the AFPR on my way back home tonight. $30 for a $140 AFPR!

Ran compressed air through the return. No blockage, or signs of a kink anywhere. Installed the AFPR, adjusted pressure to 53-54 while idling to start, and called it a night. I have pictures I'll upload later. I'll tweak pressure and the MAF over the next week or so- I drive 110-160 miles per day when I stay between metro areas, so have plenty of opportunities to datalog and flash. I immediately could tell the idle was cleaned up. It went from feeling slightly rough with no miss to smooth as our Trailblazer.

FWIW, I know there's another thread out there regarding installing an AFPR for an LT1 (93-97) F body and being a DIRECT bolt in. It's true, it's easy, and for the adjustability, it's worth it. I didn't have to tweak a thing on the truck or regulator. I don't believe a standard/OEM replacement LT1 FPR would suffice due to Gen 2's running on lower pressure than our FI system (41-47psi).

The one I used is from TPIS. With the pressure all the way down, I had 30 PSI. I can get to about 59-60 PSI running before the screw contacts the regulator.

 

nice not sure if you did but cleaning the throttle plate is always a good idea. i have an old toothbrush i use along with induction cleaner. you said you had just done bg44k so that is usually part of it. man i miss having that stuff in the dealer. i did buy one of those induction bottles to be able to do the drip kit at home. i typically just use seafoam though.

 

I cleaned the TB not too long ago- it was when I made a catch can just after Christmas. The OCC How To should be up any day now. Mine is always pretty easy- wipe it down with a towel and some deep creep. All my miles are interstate at about 2k rpm.

Found out an interesting fact. The 04-05 models with the FPR- that vacuum line does NOTHING. Double checked fuel pressure, and it was still set at 57psi, pulled the vac line, and it stayed at 57. Checked the line for the specified amount of vacuum, and there was nothing. Checked our Trailblazer with the same fuel rail arrangement, and stock resonator, and no vacuum there either. The air filter would have to be caked in dirt to produce vacuum on that side of the throttle plate. This explains why our IFR is sloped in the tune. Nothing like GM tuning out a mechanical shortcoming/oversight from the factory.

Anyway, I tee'd off the Evap line going to the TB, adjusted the IFR and VAC offset, and so far life is good.

Something else I noticed when I tested the pump volume- I just hit the release button for 15 seconds to see how much I got while the engine was running. The pressure dropped to 20psi from the 53 it was at. Is that normal- I didn't see any fuel pump volume test procedures in the manual I have.

 

Yeah it would be normal if you are holding the valve open while engine running.

posted by my Samsung Galaxy s3

 

Thanks!