Fuel pressure
 

2000 K3500, 4x4x, 7.4L, auto, dually.
I got a over rich code.
Forget what it was.
Checked the plugs, and they all look over rich.
Fuel pressure KOEO is 45 to 50psi.
But I ran it today, and got only 20psi running.
The pump has been changed last year, the regulator was changed the year before.
With the pressure so low, I'm thinking a bad pump.
Could a bad regulator cause the pressure to go that low???
I'll check it again later.

I do not think that a bad fuel pressure regulator would cause that large of a pressure drop. However, pull the vacuum line off the fuel pressure regulator and see if fuel runs out of either the fuel pressure regulator or the vacuum line. If fuel runs out of either, then the fuel pressure regulator is bad.

It;s most likely the fuel pump has gone bad. Unless you used either a GM Genuine or ACDelco fuel pump last year when you replaced the fuel pump, then the odds are much higher that the fuel pump failed. Even if you used a Delphi fuel pump, they are not as good of a quality as they were over 5 years ago.

If you purchased an inexpensive fuel pump from ebay or Amazon, you now know why it was inexpensive. If you purchased either a GM Genuine or ACDelco fuel pump from ebay or Amazon, the likelihood you purchased a counterfeit fuel pump is astronomically high.

Only internet seller I would purchase a GM Genuine or ACDelco fuel pump from is rockauto.com.

Good Luck!

On this engine, the regulator is just about impossible to reach.
Stupid design.
No idea what brand, but knowing the owner(my friend), he bought the cheapest one he could find.
I have a feeling one, or more, of the injectors might be leaking.
I'll have to dig into it more.

Do not assume anything. Diagnose, Diagnose, Diagnose. Then repair what is not right. You will save a great deal of money by not spending it on unnecessary parts.

Good Luck!

I would like to buy from Rock Auto, but the shipping to hawaii is just as much as the part.
Even with their low prices, sometimes it's cheaper for me to just get it here.

Being in Hawaii - that I understand when it comes to shipping charges.

Main point was to be careful when purchasing auto parts from Amazon or ebay because of all the counterfeit parts. Rockauto uses the same warehouses/distributors that service brick and mortar auto part stores.

Good Luck!