01 GMC 2500HD 4x4 6.0L - School me on returnless style fuel system

[410Fortune]

We own a 01 GMC 2500 HD 6.0L gas automatic 4x4 3 door
Sweet truck!

I married into this truck, it has basically sat for 2 years wwaiting to be fixed.
well now I am fixing it

truck has 154K miles on it
last summer we did:
new plugs, wires, trans fluid/filter, fuel filter, coolant flush and some other misc stuff.
Now she has a new battery, fresh gas and a 10 day temp tag

No codes, I suspect fuel problem
the fuel pump was replaced years ago, fuel lines possibly damaged I have not had a chance to look

truck is running rich if you ask me, it has a hesitation at idle, 500-600 rpm
Power loss all other times, but less noticeable at higher rpm

I have done a simple spark check, all 8 cyl triggered the test light

I figure since its a 01 it has returnless style fuel system:

1. How is this system regulated?
If this was an older truck I would suspect the vacuum operated pressure regulator

2. Anyone know what fuel pressure at the rail should be?

Thanks

 

[section525]

Does it not start the first time you turn the key?

My buddy's Cheby had a common 'Chevy' fuel problem which that is a symptom of.

 

[410Fortune]

It starts after cranking for a few seconds.
It does not fire right up like a well tuned Ford thats for sure...

more of a wrr wrr wrr wrr wrr vrooom sputter ....
seems like a miss, but who knows at this point?
I want to check fuel pressure, all 8 are getting spark

hesitation has been there the entire time I have known this truck
if it was MAS, 02, cat converter, egr, etc I would suspect a code

no codes, not yet

what was the chevy issue?

truck has two battery trays, currently running on one battery..
I want to get a look at the monkey job fuel pump replacement that was done but parts for this sucker are $$$$$
so it would be nice if we can pin point the issue

 

[410Fortune]

OKay cool after two days of driving the codes popped up

First the truck blew a heater core fitting, not surprising sine it basically sat for two years.
So I ran across town to help my brother in law who is borrowing the truck
His 03 Dodge 1500 5.7L Hemi sucked a valve the other day, he is a carpet installer so his truck is his life. So we dragged the GMC out from the side of our house, threw a battery in it, got a 10 day temp tag, checked fluids and he has been driving it since.

Two codes popped up
P0308 and P0175
Misfire Cyl #4 detected and P0175 Bank 2 sensor 2 heater circuit voltage low

So it looks like we will be trying a new coil on cyl #4
fingers crossed!

 

[JTX]

Were they still using TBI in this year? I would check the plug when you do the coil. It could be a dud new plug.

 

[410Fortune]

nope SFI this is a 6.0L LS2 engine I believe, just researching this stuff now.
It has new plugs, new wires, and a new coil on cyl #4, problem still remains.

From the Chevy's I have worked on I can tell you TBI = the big suck

I will be pulling the plug and see what it looks like tonight

 

[DB_1]

Can't help ya on the fuel issue but congrats on the truck. Will it be seeing tow duties in the future?
Aside from being a gas hog, I love my 6.0 GMC. I don't know about the older 6.0 models but the 6-speed tranny is a bit funky on the newer models. I hear it has some kind of torque management BS in there. I think that's what i'm experiencing when when accelerating off the line or coasting around a corner at a low speed then hit the gas it's like you are waiting for something to happen. Not that I want to be ricky racer in this behemoth but there are those occassions OK, so I had to show a Monte Carlo SS what's up, hey he was asking for it lol.

Sorry for getting on a tangent...back to the subject at hand.

 

[Sams01XplrSprt]

do u got pics of ur gmc

 

[DB_1]

do u got pics of ur gmc

Here ya go:
http://www.explorerforum.com/forums/showthread.php?t=211738&highlight=DB_1+joins+tow+rig+club

Sorry 410, we'll try and stay on topic now

 

[410Fortune]

update:

checked spark plugs, all 8 are good, gapped properly
Cyl #4 plug was barely hand tight, so I fixed that...
cleaned the MAS, checked all vacuum lines and hoses for leaks..

computer code went away
So the truck runs good, runs real nice on the highway, seems to have all the power but I still suspect its missing

at idle it runs like crap, smells rich, also noticed some rotten egg smell this weekend, likely the cat converters buring up the raw fuel???
500-600 RPM idle, hesitation, whole truck shakes

I am going to check the fuel system next, need to get under the truck

Do these have an IAC valve? or similar? I am sure they do

 

[410Fortune]

okay working on the GMC some more

My plan of attack for today is to check for intake leaks, clean the IAC, clean the TB, and check the fuel pressure.
New fuel filter and air filter are on the list, possibly an 02 sensor because a heater circiut code for the secondary b2s2 is popping up

So I removed the intake and engine cover.
I located the FPR, pulled the vacuum line and BAM fuel in the vacuum line

That would explain the running rich, rough idle, loss of power, etc

fingers crossed thats the last issue need to pass emissions before the 24th

 

[JTX]

You have emissions state wide in Colorado?