Advice needed.

[Lou Merrell]

1996 K1500 5.7 vortec.
I know I need cats due to structural malfunction but I'm want to get this engine right before I install new. Here are numbers from DashCommand:

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With increased engine speed:

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How do I start to decipher my fuel trims?

 

[stutaeng]

Doesn't look like a vacuum leak. Those are weird fuel trims. Is it in closed loop? Coolant temperature is not at operating temperature.

What does it do at 2k, 3k rpm?

Is this the same truck where you've had issues with the spiders?

 

[Lou Merrell]

Doesn't look like a vacuum leak. Those are weird fuel trims. Is it in closed loop? Coolant temperature is not at operating temperature.

What does it do at 2k, 3k rpm?

Is this the same truck where you've had issues with the spiders?

Yes, same truck. And, yes closed loop.
But I'm not so sure I actually have injector issues but possibly pressure regulator issue or check valve ( in fuel tank) issue.

 

[stutaeng]

Yes, same truck. And, yes closed loop.
But I'm not so sure I actually have injector issues but possibly pressure regulator issue or check valve ( in fuel tank) issue.

Did you say you had an injector that was non-responsive? Was that replaced?

What is your fuel pressure with key on engine off? Does it hold pressure within 1-2 psi for 15 minutes? What is the pressure at idle and under load?

I personally haven't seen anyone actually having a faulty fuel pump check valve. Injectors and FPR are usually a problem.

 

[Lou Merrell]

Did you say you had an injector that was non-responsive? Was that replaced?

What is your fuel pressure with key on engine off? Does it hold pressure within 1-2 psi for 15 minutes? What is the pressure at idle and under load?

I personally haven't seen anyone actually having a faulty fuel pump check valve. Injectors and FPR are usually a problem.

I'm not aware of having a faulty injector.
Koeo fuel pressure is 58-56 and does not hold for 15 minutes. Immediately starts to drop when pump shuts off reaches 20 psi in about 3 minutes. When engine is warm and sits for 5 minutes it will start but has trouble, like it's flooded No codes. Cold engine/perfect start.
It is for this reason I suspect fpr and if I'm going to replace fpr and the spider hasn't been upgraded, it will be upgraded at that time.
So, I suppose I should wait on the cats until I get my fuel system correct?
Previous owner stated that he had the complete exhaust (Flowmaster, manifold back) put on and just out of warranty one of the cats went. So it could have been caused by the fuel issue all along overheating and contaminating the cat.

 

[Lou Merrell]

My ultimate goal with the truck is to quiet it down with Walker quiet flow dual mufflers. I like hearing my vehicle, not exhaust. And even though I no longer need to get an e-check to register, I want to keep the truck running as clean and legal as possible.
Nothing worse than a loud vehicle at a remote campground also.

 

[Schurkey]

Forget the fuel trims until you get that engine up to proper temperature.

1. How old is the thermostat?
2. What temperature rating is that 'stat?
3. Is it the CORRECT 'stat for a Vortec 5.7L? (Don't they have the goofy spring and plate hanging down from the bottom?)
4. Proper coolant level and anti-freeze concentration?
5. Fan clutch works properly?



How old are the O2 sensors?

 

[stutaeng]

I'm not aware of having a faulty injector.
Koeo fuel pressure is 58-56 and does not hold for 15 minutes. Immediately starts to drop when pump shuts off reaches 20 psi in about 3 minutes. When engine is warm and sits for 5 minutes it will start but has trouble, like it's flooded No codes. Cold engine/perfect start.
It is for this reason I suspect fpr and if I'm going to replace fpr and the spider hasn't been upgraded, it will be upgraded at that time.
So, I suppose I should wait on the cats until I get my fuel system correct?
Previous owner stated that he had the complete exhaust (Flowmaster, manifold back) put on and just out of warranty one of the cats went. So it could have been caused by the fuel issue all along overheating and contaminating the cat.

Um, I could of sworn there was someone here asking about some spider and stated they had a faulty one. There should be a sticky on how to diagnose these things! At least you didn't go running changing your fuel pump because you thought the engine "was starving for fuel!" LOL

Anyway, with the information you provided about fuel pressure not holding: you most likely have a faulty injector and/or fuel pressure regulator. If you could do an injector balance test, that will find the bad injector. But seems not too uncommon to have injectors act up when engine is warm. After you shut off the engine, the fuel leaks inside, causing a flooded condition and hard starting. Similar to symptoms you describe.

The FPR can leak externally (which in these engines is still inside the plenum, causing a rich condition). They can also have an issue with the spring inside, allowing pressure to go back to the fuel tank, but not likely in your case, since the instanenous fuel pressure seems good at around 58 psi. There was a recent post where a member was having issues with a new spider. He finally removed the plenum and found the FPR streaming a huge leak internally with key on, engine off. This was a new assembly!

The way to rule out the check valve on the tank is to use to hose pinch pliers on a soft fuel line. I think all of the fuel lines on these trucks are hard line, except where the lines jump from the frame rail to the transmission underneath.

Agreed about the temperature showing too low, but you state it's in closed loop...

 

[Lou Merrell]

Forget the fuel trims until you get that engine up to proper temperature.

1. How old is the thermostat?
2. What temperature rating is that 'stat?
3. Is it the CORRECT 'stat for a Vortec 5.7L? (Don't they have the goofy spring and plate hanging down from the bottom?)
4. Proper coolant level and anti-freeze concentration?
5. Fan clutch works properly?



How old are the O2 sensors?

Yeah, that wasn't up to full temp.
Here's full temp minus stft:

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It actually got up to 189 on this view before I cut it off.

 

[Lou Merrell]

Um, I could of sworn there was someone here asking about some spider and stated they had a faulty one. There should be a sticky on how to diagnose these things! At least you didn't go running changing your fuel pump because you thought the engine "was starving for fuel!" LOL

Anyway, with the information you provided about fuel pressure not holding: you most likely have a faulty injector and/or fuel pressure regulator. If you could do an injector balance test, that will find the bad injector. But seems not too uncommon to have injectors act up when engine is warm. After you shut off the engine, the fuel leaks inside, causing a flooded condition and hard starting. Similar to symptoms you describe.

The FPR can leak externally (which in these engines is still inside the plenum, causing a rich condition). They can also have an issue with the spring inside, allowing pressure to go back to the fuel tank, but not likely in your case, since the instanenous fuel pressure seems good at around 58 psi. There was a recent post where a member was having issues with a new spider. He finally removed the plenum and found the FPR streaming a huge leak internally with key on, engine off. This was a new assembly!

The way to rule out the check valve on the tank is to use to hose pinch pliers on a soft fuel line. I think all of the fuel lines on these trucks are hard line, except where the lines jump from the frame rail to the transmission underneath.

Agreed about the temperature showing too low, but you state it's in closed loop...

When/if I change the spider I'm going to get a better fpr and install it. Most of what I've read indicate the fpr on the new spiders are an issue.
I don't have the ability to balance check individual injectors.