Anyone help with trouble shooting 6.6L gasser hard start?

[Dozerboy]

2022 chevy 2500 and I have an intermediate hard start. The engine turns over fine it just takes longer than it should to fire. First thing in the morning and if I shut it off and restart it shortly it seems to fire fine. It's after it's been parked for an hour or 2 that it seems to give me issues. I bought the truck probably about 2 months ago. I noticed it a little bit in the beginning but it's gotten significantly worse. I'm assuming a fuel pump but I've read that this code is pretty common and can be a lot of things. Truck has 63k and 2700hrs. I idle a lot, but I don't think the previous owner did. I just go me a Autel 808 scanner, but I'm not sure what I should be looking for especially since it's got 2 pumps.

Code is a 2635 fuel pump A low flow.
These are all from the fuel system data while idling.
Fuel trims look OK I guess
Fuel trim balance test failed?
MAP performance test 1 would go back and forth between Malfunction and ok: no picture
A few Ignition on Malfunctions
2 voltage References were high.

Last is a graph of fuel pressure while staying the throttle. I don't understand why desire didn't go up but I do see a dip at the beginning of actual.

If anyone can point me in the right direction of where to start looking I'd appreciate it or what websites would be good to help me flow chart how to troubleshoot this. I know there's some out there. I just don't remember what they are anymore.

 

[2004LB7]

Not sure about the newer trucks. But on some of the older ones, I believe the fuel return pressure regulator was a culprit for long starts when the vehicle sat for long enough. Pressure bled down and it took a while for the pump to refill the lines and build pressure

If you cycle the kay a few times to run the fuel pump, will it start easier?

 

[Dozerboy]

Not sure about the newer trucks. But on some of the older ones, I believe the fuel return pressure regulator was a culprit for long starts when the vehicle sat for long enough. Pressure bled down and it took a while for the pump to refill the lines and build pressure

If you cycle the kay a few times to run the fuel pump, will it start easier?

Ya GM thought this is a Race Truck and has push button start. I'm not sure if putting in in Accessory mode actually turns on the fuel pump or not you can't hear It that's for sure.

I'm not sure if that's the case though anyways because usually it starts fine in the morning. These are like diesels lift pump in the tank and high pressure cam driven pump in the valley.

 

[2004LB7]

So, it it having trouble once the engine is warm and it sits for a bit, then it has trouble?

 

[Lennydmaxguy]

Can't remember off the top of my head, does your truck have scan tool PIDs for both supply and rail pressure? If so, I'd monitor both and try to duplicate the long crank. My guess is going to be the high pressure fuel pump is leaking, although I could be wrong. We did have one in our shop with a leaking high pressure pump, and the replacement GM pump looked completely different from the old one. Apparently they had issues with some of them and switched suppliers.

 

[Dozerboy]

So, it it having trouble once the engine is warm and it sits for a bit, then it has trouble?

Yes. Seems to start fine in the mornings and if I just shut it down and restart. Like if I go into a store. If it sits for an hour or more is when it has more issues. Anything from just a little delay to 2 Mississippi’s. It was random, but the frequency has definitely increased. Almost to the point it consistently not gonna start right if I park my truck for an hour or 2.

 

[Dozerboy]

Can't remember off the top of my head, does your truck have scan tool PIDs for both supply and rail pressure? If so, I'd monitor both and try to duplicate the long crank. My guess is going to be the high pressure fuel pump is leaking, although I could be wrong. We did have one in our shop with a leaking high pressure pump, and the replacement GM pump looked completely different from the old one. Apparently they had issues with some of them and switched suppliers.

Let me look. That’s what I was thinking as well.
There’s a guy that’s trying to help me out a little bit and he had me do a balance power test and one of my bank of injectors is running lean. I’m trying some fuel injector cleaner and an upper intake clean now. At least if it’s injectors, they’re not as expensive as Duramax injectors. Not sure if I can do them myself though. He said something about needing some special tools and you had to size the O-rings.

 

[Lennydmaxguy]

Let me look. That’s what I was thinking as well.
There’s a guy that’s trying to help me out a little bit and he had me do a balance power test and one of my bank of injectors is running lean. I’m trying some fuel injector cleaner and an upper intake clean now. At least if it’s injectors, they’re not as expensive as Duramax injectors. Not sure if I can do them myself though. He said something about needing some special tools and you had to size the O-rings.

The seals are flat and wide, and seem to be made of an almost plastic-like material. They need to be stretched over the injector, then compressed in place. You just need 2 tools, a cone to slide the seal over, and a sleeve to slide over the injector. This kit looks like it would work.

 

[1FastBrick]

I looked up P2635 under a 2022 - 2500 and this is all that shows up under similar vehicles.

If it has a P018b present as well there are 7 more that show up with the same testing listed below and confirmed 7 people put pumps in them and 1 had to repair the Wiring to the Fuel Pressure Sensor. Most of those were in the 130K mile range though.

 

[JoshH]

I wonder if it's something like vapor lock.

 

[2004LB7]

I wonder if it's something like vapor lock.

That's what I was thinking when I asked about it happening after the engine warmed up