Terrible surging issues

[rockola1971]

No kidding? Its not on the chassis just under drivers side front door? Ouch!

 

[SnowDrifter]

Nope. Just a plain Jane hardline. IIRC they switched over in 2004

 

[Cattivo]

I basically had the same issues as you're having, after replacing the injectors, plugs, wires, coils, intake & maf, fuel pressure regulator, fuel filter(mine is mounted on the chassis not in the tank) it wound up being the fuel pump along with clogged cats

My best advice is drop the tank and replace the pump and filter along with using some cataclean for the cats

Cataclean

 

[SnowDrifter]

This truck is making a mockery of me.... Now it won't act up so I can check more things

So.. Working with the info I have. I pulled an upstream oxygen sensor, inspected the cat, it all looked normal. I'd be surprised if I have cat issues given that I don't have EGR and the PCV has a catch can. There's not much to foul them up lol.

Visually inspected wiring and connectors going to and from the fuel pump driver. Everything I cold access without an inspection mirror. Everything looked OK. There's no signs of rodent damage anywhere on my truck, nor has there ever been.

Theoretically if it were a stuck open injector, I'd see the fuel trims on that bank go rich, but that's not the case. They go lean. Both of them. Very very lean.

So... Seems fuel pump. To verify: A failing fuel pump driver wouldn't present the issue I'm experiencing, it would either work or not work,yeah?

 

[retiredsparky]

Low fuel pressure, lean mixture sure points toward fuel pump. No regulator or return line is very strange. I wonder if that is a previous owner modification. The pressure to the injectors would be whatever the max output of the pump is. That would seem to be ******* the pump, with no pressure relief. The continuous flow through a fuel pump helps to cool the pump.

I have worked on multiple 5.3 engines, never seen an engine without fuel regulator. That would make it difficult to control fuel mixture, since amount of fuel injected relies on a regulated pressure and the amount of time the injector is open. I wonder if there is a version that has a pressure regulator in the tank?

 

[SnowDrifter]

Low fuel pressure, lean mixture sure points toward fuel pump. No regulator or return line is very strange. I wonder if that is a previous owner modification. The pressure to the injectors would be whatever the max output of the pump is. That would seem to be ******* the pump, with no pressure relief. The continuous flow through a fuel pump helps to cool the pump.

I have worked on multiple 5.3 engines, never seen an engine without fuel regulator. That would make it difficult to control fuel mixture, since amount of fuel injected relies on a regulated pressure and the amount of time the injector is open. I wonder if there is a version that has a pressure regulator in the tank?

Returnless is the norm on post 2004 models. New law regarding evaporative emissions

 

[SnowDrifter]

Figured I'd update this. Put about 600 miles on the truck since replacing the fuel pump, no more issues.

 

[afpj]

Snowdrifter,
Thanks for keeping us informed. It will help others who end up with a similar issue, especially post 2004 models. I would've never guessed the FPR was no longer in the engine bay. I assume the filter , pump, regulator are a single unit sitting in the tank for your model year?

 

[SnowDrifter]

Yessir. All one thing.

I'm not a fan of the AIO setups but it is what it is