Low fuel pressure in first gear.

[Madscientist]

Replaced the fuel filter and got about an extra pound in pressure. It now sits around the 12 psi while driving which should be fine for the entire throttle range correct?
It's still bogging down in first gear though so I'm thinking it has to be some sort of sensor or controller shutting off the fuel pump for a second before it comes back to life.
I'll look into the wiring here in a bit. I'm guessing the signal for the fuel pump come directly from the ecm?
At any rate I'm wishing I would have put in a vortec pump in while had I had the chance, getting that fuel tank down is a real PITA.

A super easy way to do fuel pumps is to take the box off. Remove the bolts, unplug the taillights at the plug under the box by the frame. Undo the filler neck and you can lift up one side enough to get it.

 

[Doughnuts]

Alright throttle rebuild is coming up in the next week or so. Wife opened up the bank enough to order some parts lol.

So I was looking at rvmorsemachine.com and marine-performance-parts.com for there TBI parts and am a little curios about their power plate and there TBI injector spacing and wondering if that is a worth while upgrade? I have also been looking at the third gen website and it led me to these posts here.

https://www.thirdgen.org/tbi-afpr/
and
http://www.binderplanet.com/forums/...djusting-the-fuel-pressure.50514/#post-298293

So I'm wondering if there is a difference between the two TBI set ups. I have taken a look at mine but without taking it off I am not sure. I do have on from a junkyard that I practiced on whenever I did the TBI mods and it seems to have a small nipple version of the
spring housing. So I don't believe its adjustable.

And as long as we are the subject, on rvmorsemachine website it states that...

"This Tbi Adjustable Regulator is needed for stock and modified GM tbi engines. At 3/4 to WOT the computer uses a fixed program for max power. Therefore,since it is not reading the A/F ratio you may need more or less fuel for maximum power. This regulator let's you change what the computer can't."

So what would be the proper pressure for WOT operation? I'm not trying to make a drag truck or anything but I don't want it running lean either.

As for the tank related questions I filled it up with half a tank so I doubt its an air in the system problem and I'm hoping to leave the pump in unless I have to. And if I do have to do it again ill try out the bed removal method. might save me from getting gas in my armpits

Thanks for everyone's help! this has been awesome getting some of the things fixed on the old truck!

 

[PlayingWithTBI]

So what would be the proper pressure for WOT operation? I'm not trying to make a drag truck or anything but I don't want it running lean either.

You need to data log and watch your INT and BLM to see where you are while driving around, s/b ~128 (14.7AFR stoich). The best way is with a WBO2 (Wide Band O2) sensor which will give you feedback throughout the power band, instead of just high or low as the stock NBO2 (Narrow Band O2) will. There's quite a bit to tuning these parameters but, that's what makes it so fun.

Another link for TBIs and parts - I bought the 46mm bored TB (among other stuff) from him and have had good luck with it.

https://www.ebay.com/str/sprperformance

 

[Supercharged111]

You need to data log and watch your INT and BLM to see where you are while driving around, s/b ~128 (14.7AFR stoich). The best way is with a WBO2 (Wide Band O2) sensor which will give you feedback throughout the power band, instead of just high or low as the stock NBO2 (Narrow Band O2) will. There's quite a bit to tuning these parameters but, that's what makes it so fun.

Another link for TBIs and parts - I bought the 46mm bored TB (among other stuff) from him and have had good luck with it.

https://www.ebay.com/str/sprperformance

46mm is bored out? I think my LT1 is 47 or 48 stock. I have one that's bored out to 50mm, 52mm is a more common size for that application from what I've seen.

 

[PlayingWithTBI]

46mm is bored out?

Yep, they say the 46mm Throttle Body will flow 650CFM which is good enough for my 5.7L @ 6000RPM. I've tried 28PSI on 61LB/Hr injectors but they started dribbling causing a bad stumble so, I tried 7.4L ones (~80 LB/Hr) with 18PSI and had problems getting it to idle so, I went back to the 61LB/Hr and lowered my pressure to 20PSI (18LB spring screwed in) and it seems to be OK but at WOT in 2nd gear @5200RPM my DC (Duty Cycle) is right at 100% with AFR ~12.2 and MAP @90

Edit, I also bored my Edelbrock Performer 3704 out to 48mm to fit the TB.

 

[Supercharged111]

Shoot, 12.2 is pig rich for an NA truck. Not sure about the GenIs, but the LS motors seem to like it 13:1 or so.

 

[PlayingWithTBI]

Shoot, 12.2 is pig rich for an NA truck.

Yeah, that's my next endeavor - to fine tune my PE AFR commanded table. I was adding fuel to see if I can reduce KCs. I got rid of them but, as you said, I'm running rich now but, it helps to keep the combustion chamber cool, LOL.

 

[CrustyJunker]

Shoot, 12.2 is pig rich for an NA truck. Not sure about the GenIs, but the LS motors seem to like it 13:1 or so.

I know this is off subject from the original thread. I heard TBI stuff (factory intakes/heads, anyway) like slightly richer fueling because of poor fuel distribution at higher RPM's.

The cylinders that go lean will usually start knocking first on datalogs. When flow gets up there - aftermarket cams and increased displacement make matters worse sooner in the powerband...There's supposedly some power killing turbulence going on.

Havoc starts in TBI intakes from the bottom of the throttle bores to the intake runners (nearest the intake floor), and again over the swirl port head step. It's great for torque and efficiency, not so much for performance. Carb style intakes and port injected guys don't seem to have this distribution problem...And most traditional style heads will fix the high RPM cylinder fill issues.

My truck started falling on its face above 12.8:1 on pump E-10. Not sure if the E-10 contributed, but this was with a bored out factory intake and aftermarket heads.

 

[PlayingWithTBI]

My truck started falling on its face above 12.8:1 on pump E-10. Not sure if the E-10 contributed, but this was with a bored out factory intake and aftermarket heads.

What kind of heads? Here's what I have...
https://www.summitracing.com/parts/sum-162108/make/chevrolet

 

[CrustyJunker]

What kind of heads? Here's what I have...
https://www.summitracing.com/parts/sum-162108/make/chevrolet

I'm running very similar. Running Trick Flow Super 23's, also 62cc chambers, except 195cc runners.