2003 vortec 6.0 - fuel pressure problems

[westman995]

I am trying to diagnose a 2003 silverado with the 6.0 vortec in it. Fuel pressure is around 40 psi key on engine off and while running. It goes up a little bit while running or revving it up but not much. The truck starts up no problem but it runs like crap.

My main question is can it be the fuel pressure regulator causing low pressure? There is no gas coming out of the regulator. Unplugging the regulator makes zero difference in how the truck runs. The truck had a pump put in it not long ago so id hate to replace it if its not bad, But its looking like thats going to be the problem, just need to know if the regulator can cause low pressure

 

[Red Rider]

Sorry, can't help you there. could not even find the fuel section of the FSM in the digital version.

Just out of curiosity, what brand pump did you buy? Let us know if it ends up being the pump.

 

[westman995]

I cant find anywhere online about the regulator either. The only thing i see people say is pull the line off the regulator and if fuel comes out its bad, they dont say it can be bad any other way.

Im not sure what kind of pump it was as i did not put it in. I know it wasnt an ac delco so i have a feeling it can easily be the pump. The guy has dumped a bunch of money into the truck trying to figure out the problem. The places he was taking the truck to were obviously just throwing parts at it cuz they had him put injectors, coil packs, o2 sensors and all kinds of shit on it for no reason..

 

[Red Rider]

There are about 10-15 different pumps for this truck. I am sure there is some junk out there. A bad mechanic would throw the cheapest part in there and it could fail prematurely. Probably what happened.

 

[westman995]

Like i said my guess is the pump as well, and if it were mine i would swap it out for an ac delco either way and get it over with. But with all the money hes already wasted on other parts that im sure were not needed, Id hate to throw more unnecessary parts at it. I just dont understand 100% how the regulator works so not sure if that could be the problem.

 

[01ssreda4]

That's funny cause my 03 doesnt have an external regulator. Mine is built in to the pump.

 

[westman995]

You sure theres not one on the fuel rail? Is it a silverado too? Id assume it would be the same either way tho.

 

[westman995]

Alright so I replaced the fuel pump with an ac delco. While it does run alot better than it did it still isn't running right. It still has the p0300 if you drive it.

I feel like the fuel pressure is still not high enough. I believe it was only at about 50 at idle. Put a new fuel filter on it too.

If I unplug the vacuum on the fuel pressure regulator the pressure does go up. Can the regulator still cause low pressure? I don't know what to try next..

 

[Chizzychase]

having similar issues on my 04. 40 PSI at key on and holds there after key off. Running its about 45-50. We discovered this yesterday while I was at my tuners shop getting it tuned. He said it shouldn't be that low at all. I thought I remembered seeing something about the regulators going bad in these vehicles (tahoe, yukon, silverado, sierra) but im not sure.

One solution my tuner came up with was to put an aftermarket regulator on it with a returnless style fuel rail and manipulate the pressures from the regulator to get the pressures where it needs to be.

I'm not sure on the years for external or internal regulators but if the new AC delco assembly did not have a regulator built in and after you put it on the truck and it didn't fix the problem I'd almost be willing to bet the regulator is your problem

 

[westman995]

The pump doesn't have a regulator as far as I know. It has one on the fuel rail. Could the regulator not allow full flow?

The pump I put in was the ac delco mu1613. Which apparently wasn't the exact one I needed. It has the two plugs on it but the truck only has one plug. I don't think it's gonna make a difference tho. As far as I know it's the same exact pump as the other one for this truck but with that extra plug/sensor thing.

The other weird thing is when I turn the key on the pressure goes up to almost 60 I think it was but then almost instantly drops to around 50 and it will stay there. It doesn't drop anymore after that. I wonder if that is normal or not. Seems kinda weird