Am I right on my Troubleshooting codes PO171 & PO174?

[Nodnarb76]

I've got 12,00 miles clocked on my 6.0 LS swap from 3 years ago.
Yesterday when driving around, CEL came on. I checked for codes and got PO171 & PO174 lean condition on both banks.

When I did my swap, I installed a fuel pressure gauge on the fuel rail.
I noticed I'm getting 40 psi (according to the gauge). I'm thinking this is the cause of my problem.

Could my fuel pump be bad? I used a Walbro 255 that was brand new, would it have gone bad in 3 years/12,000 miles?

Also what are the odds either my filter/regulator is clogged or maybe the inline fuel filter under the truck is clogged.

I know to also check for vacuum leaks, but If my gauge is correct on the fuel rail I'm guessing my fuel pressure is too low.

[sprint_9]

What filter/regulator are you running? The Corvette one? What brand is it?

[Nodnarb76]

Originally Posted by sprint_9

What filter/regulator are you running? The Corvette one? What brand is it?

I am using the corvette filter. I got it from Napa.

[sprint_9]

I would probably try replacing it first if you have no evidence of anything else being wrong. Ive read about random issues with them on occasion. Even though I think most Napa stuff is Wix I would get an actual Wix filter, they seem to be less problem prone based on the same reading.

[BR3W CITY]

FWIW I believe napa switched away from WIX as their primary filter supplier.

[Nodnarb76]

Thanks for the help guys.
I think that is the path I will take.
I'll replace the regulator and inline filter, and then seafoam the motor at the same time.
If that doesn't do it then I will replace the fuel pump.

[1971Stepside]

I would like to see your gauge set up on your fuel rail. I would like to do that, but was not sure of the fittings needed etc.

Thanks in advance.

[BR3W CITY]

Mines right off the rail.

[Nodnarb76]

Here is a pic of my fuel pressure gauge.
I am going to replace it when I do the rest of the work just to make sure it is accurate.

[1971Stepside]

So you aren't using the Shrader valve then? Hooking them up where the line goes into the rail? Maybe your rail is different than mine and this is where yours is located.

[BR3W CITY]

Those gauges are in-line to the feed line on the rail.

The schrader location will also work, but then you lose an easy hookup for wet kit fuel lines.

[Nodnarb76]

Before I start buying parts, I wanted to ask this:
If the fuel pump was bad, would I be getting 40psi at idle?
I would think if the fuel pump was bad I wouldn't be getting any fuel pressure.
I also was thinking the hose between the fuel pump and the sending unit (I used fuel injection hose during the swap) may have come loose/failed. If that was the case could I be getting 40 psi?

[ls1nova71]

I've had the hose between the pump and sender get a pinhole in it and not build as much pressure, and I've had it almost totally blow out. The time it almost totally went, I was just getting on the highway and lost almost all power, but was able to limp it to work and back home. If that hose is loose, it may do the same thing. If that is good, my bet would be a filter/regulator before the pump though.

[Nodnarb76]

Originally Posted by ls1nova71

I've had the hose between the pump and sender get a pinhole in it and not build as much pressure, and I've had it almost totally blow out. The time it almost totally went, I was just getting on the highway and lost almost all power, but was able to limp it to work and back home. If that hose is loose, it may do the same thing. If that is good, my bet would be a filter/regulator before the pump though.

Thank you for confirming my ideas.
Its funny I was a service advisor for a car dealership for 17 years. I Could pretty much tell what was wrong with a car before it went back into the shop.
Quite a few times I have even helped the techs diagnose and fix cars. So when it comes to fixing car I feel pretty confident that I know what I'm doing.
When it comes to my own cars, I am always second guessing myself and like to ask for other people's opinions. Funny how that works.

My job changed a few months ago, I still work for the same company, but now I have been moved to the corporate office and don't have access to the shop I used to. If I have to drop the tank I will have to pay someone to do it as I don't want to tackle that job in my driveway.

I will stick with my plan A: replace regulator, filter, gauge on the rail, and then seafoam the motor. If that doesn't fix It I will drop the tank and check voltage at the tank, check the hose between the pump/sender, and replace the fuel pump while the tank is out.

[truckdude239]

might be worth spraying your intake gaskets with brake clean to make sure you dont have any intake leaks,

[Wgesnerjr]

If there was and intake leak and brake clean was used to find it, could it possibly damage to o2 sensors? I remember someone teaching me to not use carb cleaner on a fuel injected engine. Only throttle body cleaner to avoid messing up o2 sensors.

[truckdude239]

in fine ammounts it wont hurt it at least it never has for me

[Wgesnerjr]

Ok, Good to know.

[Nodnarb76]

I had another Idea I would like to run past everyone.
Because I'm getting 40psi at the fuel rail, and I'm not sure if I'm dealing with a fuel pump or regulator issue, I was thinking about temporarily re-locating the fuel pressure gauge between the pump and the regulator to check what the pressure is coming from the pump.

Does anyone have an idea of what pressure I should be seeing at idle from a Walbro 255?

[BR3W CITY]

Originally Posted by Nodnarb76

I had another Idea I would like to run past everyone.
Because I'm getting 40psi at the fuel rail, and I'm not sure if I'm dealing with a fuel pump or regulator issue, I was thinking about temporarily re-locating the fuel pressure gauge between the pump and the regulator to check what the pressure is coming from the pump.

Does anyone have an idea of what pressure I should be seeing at idle from a Walbro 255?

[Wgesnerjr]

I did this same thing when I was fighting an over rich issue on start up.

http://67-72chevytrucks.com/vboard/s...=774609&page=3

I when to the hardware sore and found a brass fitting to install into my fuel pressure gauge. I then rigged up a way to connect it after the fuel filter and before. Both tests pegged my fuel pressure gauge. Like over 100PSI. Hope that answers your question.

Also during this process, I learned that my motor is a Flex-Fuel motor and runs at a slightly lower pressure. Like in the 40s psi is normal for my engine.

Now that I have the O2 sensor fixed, the truck runs GREAT on the 40psi! Lots of power and no hesitation at high rpms, etc.

[Nodnarb76]

Thanks for the help everyone.
I will try to re-locate my gauge on Saturday (if the weather is nice) and see what the fuel pressure is before the regulator.

[nobox351y]

I would also check voltage to the pump or wiring. When I initially did the fuel setup on my swap I used an aeromotive stealth pump, the original wiring was the death of that pump with in a couple weeks.

[Nodnarb76]

I was planning on checking that as well.
I have a dumb question though.
I should see 12v at the pump all the time correct?
The ECU wouldn't vary the voltage to the pump for any reason would it?

[ls1nova71]

The PCM doesn't vary the voltage in a GenIII, it just turns on the fuel pump relay which delivers a full 12v, but only as long as it's on. The PCM will turn the pump on for a couple seconds, then shut it off if the engine isn't running, so be aware of that when checking your voltage. You can either jump the terminals in the relay or have someone turn the key on for you while you check it.