1997 K2500 Suburban 454 Fuel System suggestions

[Supercharged111]

Injectors and FPRs are notorious leakers. I've heard of people taking the plenum off, cycling the key, and watching fuel dribble out of the injectors.

 

[L29Sub]

A Vortec FI is.a creation from hell. As has been stated, increasing the injector size is pointless. Your ECM doesn't have maps for them, and the O2 sensor limits air/fuel ratio in any event. Replace the injectors and fpr. Use GM fpr kit. You cam clamp the fpr sense hose and see if the engine idle cleans up. If the fpr is leaking internally, it'll muck up the idle.
You could have a rocker bolt backing out, or a bad/damaged lifter packing. I'd go with leaky lifter since it quietens up with oil. But you'll be revisiting that soon enough. If it raps too much, it'll hammer the roller off the lifter. Then you got major issues. You cannot adjust the lash on Vortec 7.4.
While under the plenum, you can get to the valve lifters pretty easily. They are not expensive.
If loose rocker stud, lock it down.
These engines leak at the rear lower plenum. It must be chemically clean and the correct sealant used per the book.

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[ZRoe]

A Vortec FI is.a creation from hell. As has been stated, increasing the injector size is pointless. Your ECM doesn't have maps for them, and the O2 sensor limits air/fuel ratio in any event. Replace the injectors and fpr. Use GM fpr kit. You cam clamp the fpr sense hose and see if the engine idle cleans up. If the fpr is leaking internally, it'll muck up the idle.
You could have a rocker bolt backing out, or a bad/damaged lifter packing. I'd go with leaky lifter since it quietens up with oil. But you'll be revisiting that soon enough. If it raps too much, it'll hammer the roller off the lifter. Then you got major issues. You cannot adjust the lash on Vortec 7.4.
While under the plenum, you can get to the valve lifters pretty easily. They are not expensive.
If loose rocker stud, lock it down.
These engines leak at the rear lower plenum. It must be chemically clean and the correct sealant used per the book.

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Wouldn't the 0411 PCM swap fix the mapping issue?
Are the O2s still a limiting factor when tuned with the new PCM?
I probably haven't done enough reading, but this is the first time I've seen these issues in writing. I'm very curious to know if I'm barking up the wrong tree. Would save me a lot of headache and money.

As for the tick, I appreciate the input. I'll be on the lookout for a loose stud. Hoping it's that simple. Not really excited about pulling the lower intake if I don't have to. It really isn't leaking enough to notice yet.

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[ZRoe]

Forgot to mention, the injectors are NOT leaking and the FPR is NOT leaking out the vacuum control.
Fuel pressure only gets to 54psi and drops immediately to 50psi when I shut the pump off, then falls to 40 over the next few minutes.

I'm leaning towards damaged o-rings on install as I would have expected closer to 60psi (4 bar is 58.8psi) with the pump on?

I'll ask the auto parts store about the fuel pump having an anti drain back valve tomorrow when I grab a replacement FPR

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[L29Sub]

If you have fuel puddled in the intake, something isn't right. Slow cranking speed could cause issues. What you are looking at is a minimal fuel pump. Or, a bad regulator. Or both. The pump has borderline pressure (about 60 is desirable) and either an injector, regulator, or fuel pump, or all of the above are worn to the point of replacement. The pressure should hold for 15 minutes or thereabouts as it gradually decays. A word of caution...if you replace the fuel pump, go with a complete unit from GM dealer. Roughly $500. All aftermarket pumps are Chinese garbage. Too much trouble to fool with. Some cheapies work for a month...or a year. But you'll be walking given time. Injectors with more than 150k are worn out. Maybe Accel or some such in 20 lb would be OK. The regulator can be repaired. And the injector wiring harness is brittle and the plugs fragile. That's why I went carb. Got tired of dinking with the OEM system. Add to this a moderately worn engine with worn valve seats and low compression. Or worn cam lobes. Your fuel pressure and decay rate indicates a 'bottom feeder' fuel pump.
Here's the solution...note the Q'jet fuel injection. Best thing ever created for Chevys. If you have an automatic, this could be a bit more complicated.

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[L29Sub]

One more thought. The plenum and lower are a lot of work to remove. While you're in there, do a set of lifters. They are not gawdawful to buy and you're better than halfway there. The rockers are bolted down. No adjustment. Occasionally a rocker bolt will back out. You could pull the valve covers and verify. The pax valve cover is covered by the throttle body and cannot be removed with the intake system intact. And, you could seal up that leak at the back. I'd do a compression test and make sure you have good compression. Look for an odd reading and you might pick out the loose valve.
That valve noise could become s disaster if the lifter grenades. How many miles on your engine?

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[ZRoe]

Thanks for the input again!

I already have the plenum off, didn't put it back on yet because I was having funny pressure readings.

Going to Qjet fuel injection sounds fun but this is more of a DD than a weekend rig for a while yet and I don't know if I want to deal with a Qjet in a Michigan or even MN winter.

I'm working on getting the valve covers off next but the pesky CA emissions AIR pump lines are covering them up and I don't want to strip anything until I get the chance move forward with the tuning.

I've got a few busy nights ahead so I may not have much for updates until Monday.

I guess it's a good thing my wife's old car never sold. So I still have something to drive.

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[454cid]

q-jet fuel injection??? Whats' that?

 

[Christian Steffen]

Wouldn't the 0411 PCM swap fix the mapping issue?
Are the O2s still a limiting factor when tuned with the new PCM?
I probably haven't done enough reading, but this is the first time I've seen these issues in writing. I'm very curious to know if I'm barking up the wrong tree. Would save me a lot of headache and money.

As for the tick, I appreciate the input. I'll be on the lookout for a loose stud. Hoping it's that simple. Not really excited about pulling the lower intake if I don't have to. It really isn't leaking enough to notice yet.

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Those should be a good injector size, that or LS6 injectors are little bigger yet. The stock size is just barely adequate in the stock trucks I've tuned, so a little bigger is a good idea.

A Vortec FI is.a creation from hell. As has been stated, increasing the injector size is pointless. Your ECM doesn't have maps for them, and the O2 sensor limits air/fuel ratio in any event. Replace the injectors and fpr. Use GM fpr kit. You cam clamp the fpr sense hose and see if the engine idle cleans up. If the fpr is leaking internally, it'll muck up the idle.
You could have a rocker bolt backing out, or a bad/damaged lifter packing. I'd go with leaky lifter since it quietens up with oil. But you'll be revisiting that soon enough. If it raps too much, it'll hammer the roller off the lifter. Then you got major issues. You cannot adjust the lash on Vortec 7.4.
While under the plenum, you can get to the valve lifters pretty easily. They are not expensive.
If loose rocker stud, lock it down.
These engines leak at the rear lower plenum. It must be chemically clean and the correct sealant used per the book.

Sent from my SM-G965U using Tapatalk

Aside from ****** injectors and FPR from the factor there is nothing wrong with this system. With software the stock computer can even be changed, but the 0411 makes things much much easier. The injector data can be copied from corvette tunes. The o2 sensors DOES NOT limit the AFR. There is a power enrichment delay that GM tuned in that keeps the truck at stoich at WOT for 60s. If you have it tuned/0411 swap your tuner can make PE come on whenever you want. When PE mode is enabled it disables that O2 sensors.

 

[Supercharged111]

The PCM can be tuned for larger injectors, but again why do you want them? If you have a tick, don't be surprised if you ate a cam. Mine did and it's not that unusual in a big block.