Bad fuel pump?

[PlayingWithTBI]

What really surprises me is, OP didn't get any codes, even without O2 sensor feedback WUWT???

 

[Erik the Awful]

The factory plastic intake gaskets are notorious for sucking inward and causing a vacuum leak. That would cause one bank to be leaner than the other. That's where I'd start investigating.

 

[VIKING_MECHANIC]

The factory plastic intake gaskets are notorious for sucking inward and causing a vacuum leak. That would cause one bank to be leaner than the other. That's where I'd start investigating.

When the head gaskets blew a few months ago, I had both intake manifolds cleaned and all gaskets replaced. The injectors were also pretty clean looking too. I didn't replace the pressure regulator even though I had the chance. But I don't know if it was leaking as I never took apart the manifolds.

 

[bigshane]

When the head gaskets blew a few months ago, I had both intake manifolds cleaned and all gaskets replaced. The injectors were also pretty clean looking too. I didn't replace the pressure regulator even though I had the chance. But I don't know if it was leaking as I never took apart the manifolds.

When something's "just been replaced" paradoxically makes it far more likely to be the culprit. It often pays to start diagnosing there first.

 

[Steve A]

Rich on bank 2 could be the fuel pressure regulator as that's the side it's on. And if it's constantly rich I would think the computer would pull fuel to lean the motor out but only in closed loop, should be running off a fuel table in open loop until it warms up.

 

[VIKING_MECHANIC]

Rich on bank 2 could be the fuel pressure regulator as that's the side it's on. And if it's constantly rich I would think the computer would pull fuel to lean the motor out but only in closed loop, should be running off a fuel table in open loop until it warms up.

The regulator is attached to the metering body and kinda in the middle rear of the upper manifold so it's not necessarily on one side or the other. Although after reading through the Hanes manual, gave me more ideas of what it may be.

You must be registered for see images attach

 

[VIKING_MECHANIC]

So I did more research on what may be going on. I read through the Hanes manual and noticed how the injectors/metering body are assembled.

I did notice that the required psi to run is 62-66, so my 50 definitely isn't good. I did see a way to test the injectors/regulator.

They said to install a shut off value on the return line, and let the engine run for a while. Shut it off and watch the psi. It should not drop more than 5 psi over a 5 minute period. If it does drop, then there's a leak in a line, injector or pump check value is defective.

There's a lot more than that I read, but it's a start to what may be going on. Also, I'm not sure how to install a valve on a fuel line.

You must be registered for see images attach

 

[Steve A]

The regulator is attached to the metering body and kinda in the middle rear of the upper manifold so it's not necessarily on one side or the other. Although after reading through the Hanes manual, gave me more ideas of what it may be.

The regulator is as you say on V6 models (as shown in the Haynes manual 14.11) but your C1500 is a 5.7 correct? The regulator is on the passenger side as the "fuel meter body" is rotated 90* from the V6 orientation.

 

[darkdelta]

Alright, so for the last few weeks, I've been having issues with my C1500 running. I can feel it shuddering, sometimes I can barely feel it and other times It feels like the entire truck is shaking.

So I look at the live data to see what is going on and this is what I see:

You must be registered for see images attach

You must be registered for see images attach

Okay, so one bank is running lean and other is running rich. Got it but not really helping me figure this out. I ended up replacing the MAF because I will sometime get a "no signal/low voltage" code. Usually cleaning the MAF and the codes go away. I figured it was time to replace it because I was thinking the ECU wasn't getting the correct information and was adjusting the air/fuel accordingly. I replace it about a week ago and I'm still having this issue.

I got home from work today, and checked the fuel pressure. From what I understand, the operating range for these Vortec engines is 62-66PSI. I turned the key on and the system primed to 60PSI. I started the engine and it fell to 50PSI and held there while running. I tried the test a few different times and every time it would prime to 60 and drop to 50 when running.

Do these pumps show any sign of early failure? I don't think this is because of a clogged filter/strainer or a restriction in the line as it happens rather randomly. I have noticed though it will seem to favor to do this in the morning when the air is cool and dense. And with the engine running both lean and rich at the same time, I'm at a loss on that.

What's you guys' take on this?

My fuel pump gave me a single heads up it was going to fail. Leaving a shopping center the truck had a long crank time, started up and never made it out of the shopping center parking lot. The engine shut down. Restarted with another long crank.Drove a short distance home. Parked it in the driveway. A couple of days later, I started the truck up, went back inside to get something. Returned to a stopped engine. Tried to start the old girl, key on, did not hear the fuel pump prime. Ended up replacing the fuel module (new name for me) and as a bonus, I got to replace the gas tank due to rust in the thing. At least it had the decency to do this in the driveway. 1998 C1500 WT 4.3L 127 K on the clock. I think everything was original.