2014 Silverado erratic fuel pressure---what would cause this

[Lakegoat]

5.3 bored and stroked to 408. Ported heads, forged internals. ZL1 fuel pump, FIC LT4 30 over injectors, Magnuson SC, 240/250 cam with +33 percent fuel pump lobe. 6L80 trans.
Starts and idles fine. Idle timing is all over the place
The short log is just sitting still and giving it a little gas. I'm afraid to drive it like this.
Fuel pressure is NOT steady. Fuel pressure Looks like the idle timing log.
Came back from a shop that could not finish the job.
Anybody know why the fuel pressure is so erratic. I am not familiar with the E92

[ShaneB]

you didnt post any logs bud

[Lakegoat]

Dang it
Posted now

[ShaneB]

you should also log the requested low side pressure as well as high side rail pressure. my camaro jumps around a little bit on the low side as well, but the high side is always consistent. i think its just the nature of returnless systems on di cars. i am a noob though, fwiw

[sevinn]

Agreed. I'd take a look at what's going on with actual rail pressure. The b2 o2 seems really erratic too.

[Lakegoat]

Thanks Shane and sevinn, I will get those in my channels.
I saw the B2/O2---but wanted to get some other things sorted. Thanks

[Lakegoat]

Here is a short running log, idle to about 2500 rpm sitting still. Fuel pressure follows requested fuel pressure, but why does it decrease with a little throttle?

[jasonz28camaro]

I got a zl1 pump on mine and the pressure does the same thing. I guess its a the PWM thing. I have roughly the same pressures on a log I looked at just driving around the block. I'm no expert though so mine might be messed up too lol.

[sevinn]

Here is a short running log, idle to about 2500 rpm sitting still. Fuel pressure follows requested fuel pressure, but why does it decrease with a little throttle?

Everything looks pretty good other than that o2 to me really. Desired is following commanded. It's commanding less hi side pressure because ECM - 17071 - Desired Fuel Pressure is commanded less hi side pressure at the cylinder airmass you are reaching when you throttle it up a hair.

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[Lakegoat]

OK, makes sense. Is that chart stock or modified?
Plugs are BLACK --Brisk Racing Silver RR12YS

[sevinn]

OK, makes sense. Is that chart stock or modified?
Plugs are BLACK --Brisk Racing Silver RR12YS

That is the chart that was in the tune you posted. Looks stock to me. I'd say those plugs could be a reason it looked like bank 2 was misfiring.

You've got a massive fuel trim imbalance so bank 2 is commanding about 20% fuel at all times.

[Lakegoat]

Unfortunately both of those plugs are from bank one LOL---
Time to get under the truck.

[jasonz28camaro]

I got a zl1 pump on mine and the pressure does the same thing. I guess its a the PWM thing. I have roughly the same pressures on a log I looked at just driving around the block. I'm no expert though so mine might be messed up too lol.

I think mine has issues too now that I think about it and my engine light came on... I got code P2635 and I believe its because of my fluctuating/low pressures. According to my WOT logs I'm roughly 20psi short of whats being requested. Your tune looks to be the same as mine in this area too (truck OS) so it might be worth dialing this area in too if this is the case.

Under fuel system/fuel pressure/desired fuel pressure you have normal and high flow. These pressures look to be good but they do not seem to account for the Maximum pressure limits in the same section. Yours and mine both drop pressure while the flow rate increases, this is probably due to the truck OS calibrated to the truck pump and not the ZL1 pump if I had a guess. I havent logged my flow rate yet but according to the table I'm at 52psi at WOT rather than the requested rate of 72psi, adjusting the table should raise the WOT psi. If you open a compare file of a more performance-related vehicle (camaro/vett) you will see how their max pressure limit table is higher than the trucks. This is all low pressure side stuff too by the way, I dont have enough power to be concerned with modifying the HP side. As you know you don't want to starve the HP side though.

If you already know all this or I'm wrong just disregard this. I'd appreciate it if someone has a better approach on this?

[Lakegoat]

Thanks, I will check that out. I am kinda starting from zero on this Gen 5.
I downloaded a ZL1 file for the right pump numbers.