It was running great on Tuesday when I flew out and it was acting weird when I drove it on Saturday when I got back. Would a fuel pump be that sudden? Is is possible it could be bad gas, or would that be at all ranges?

As far as the lean codes go, I suspect a vacuum leak as I can hear a loud hissing coming from the passenger side manifold but I have been unable to find it.

 

How many miles on the truck? My stock pump started dropping fuel pressure from 4000+ and that was happening for IDK how long. Put a new 255 walbro in and pressure holds nice and steady.

 

120K on the truck. I'm just making sure this is all stock in the fuel system before I go buying pump(s).

I know the fuel filter is on the left in this picture, is that an inline pump on the right?

 

Yes that is a in line pump then there is a pump in the tank as well. So the owner before you.added this on most likely when the SC was added. Maybe one of these two pumps have quit working and maybe one pump by itself can't support your fuel needs so its starting to act this way.

 

Well when I prime the pumps by putting the key into the "on" position I can definitely hear a buzz from the in-tank pump; however, I hear nothing from the inline pump even when right under it. Should there be an audible buzz from both pumps when priming?

Also, there's some cracking in the lines connected to the fuel pressure regulator. They don't look major and I wouldn't think those would cause the problem suddenly, but I will replace.

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To add one more thing. My truck has never really held fuel pressure with the engine off since I've had it. When doing the injectors I never had any pressure bleed off even when trying to relieve it right after having the engine on to test. Just some more food for thought if it makes a difference.

 

Sounds like you have two problems. The in-tank pump check valve has failed or the FPR on the fuel rail has failed (or both!) and is dumping the pressure back to the tank. The other problem is your in-line booster pump has probably failed. With power going to the pump (wouldn't hurt to check for voltage) you should feel/hear a light vibration.

Do a fuel pressure test with that Schrader valve, engine off. Turn the key to the Run position, the pumps should prime and you should see at least 50psi of pressure. If it dumps right after 2 seconds I would suspect the check valve or possibly the FPR to be defective.

The next step is to hotwire the pumps by jumping the fuel pump relay connections in the fusebox to turn the pumps on. The engine still needs to be off at this point. You should see 55-60PSI, if you see less you have a dying fuel tank pump (the inline pump is a booster pump, fuel will still flow through if dead). Get a handheld vacuum pump (the kind with a hand trigger for pumping) and hook it to the vacuum port on the FPR. Apply vacuum and see if the fuel pressure falls any from it's atmospheric reading. If nothing happens by the time you reach -20 vacuum you have a defective FPR.

 

Ended up being the inline fuel pump. It was leaking gas from the internals when it was taken apart. Got a new Walbro in there any the truck is finally getting the advertised PSI!

 

Glad you got it figured out. Thanks for giving us an update.