2022 L8T occasional hard start

dozerboy · December 28, 2024

Hey Guys I could use some help. I have a truck that new to me that I'm trying to diagnose an occasional hard start on. It's a 2022 silverado with an L8T. That has gotten worse over the last 3 months of ownership. Truck starts fine except after its been sitting for about 2hrs. Then I have long crank times. Truck start fine in the morning though. I have no "CEL", but a p2635 fault. I'm dropping fuel pressure and will set a code if I run the ****** out of the truck, but only then and it will "clear" itself. Useing the troubleshooting procedure outlined by GM according to the code I've found online. Im using a Autel 808 to Depressurize the fuel system durring a cold idle. After the truck dies the sensor is still showing pressure 30psi-100psi after the engine stops. How would you verify the sensor/wiring vs the fuel control module? And there is it? Its not on the supply line thats visible, but from some videos it looks to be on top the tank by the bulkhead. I still think I might have a bad pump too. At idle the command is 80% (engine warm) and the pump is running a 7k RPMs. Thoughts or suggestions? Not a lot out there on these engines. I also have weak injectors on bank 1. I'm not sure how that could be attributing to my issue. I hate swapping parts just for the sake of swapping parts but I'm getting to that point almost.

I can try and post some photos of the scan tool values if I can figure out how to resize them.

bruceb58 · January 1, 2025

There are two pressure sensors...one is to control the fuel pump pressure in the tank and the other is on the high pressure fuel rail. I have a feeling your depressurize command is for the high pressure rail but that's just a WAG.`

There is a one way check valve after the tank fuel pump to maintain pressure in the line to prevent long starts.

I have the service manual and there are a number of things to check, You may just want to take to some one who services these trucks or the dealer. Shotgunning parts is going to be an expensive endeavor.

Are you not under warranty?

How do you know you have weak injectors?

Edited January 1, 2025 by bruceb58