Fuel tank/pump pressure sensor

[Wpolonavyguy]

I've been struggling with evap system problems & leaks for some time.
Replaced fuel pump 4 times as a couple purchased from Amazon for lower prices were wrong or inferior products, one had too many ports which plugged cap leaked then replaced with two port seemed good plastic swelled in fuel broke into pieces trying to remove from access hole now too small .
Current pump seemed ok still getting random air leaks & rich mix codes.
Anyone know live data pressure readings at idle supposed to be?
I've been seeing -1.482 mmHg?
Can anyone tell me correct fuel tank pressures?
I replaced gas caps three different types & drivers indicator sometimes says check gas cap sometimes.
I've checked all connections & replaced evap lines. Last effort soon is removing charcoal canister again & put new in and check if anything in tubes.
Some others say canisters can clog the evap tubes.
Which line usually gets canister gunk dumped/ plugged in?

Control circuit code was my testing x3 evap solenoids at fuel rail, all had seal no air leak. One made clicking noise loud like a lifter failing scared me. Found exaust nuts loosened some at cat/header joints possibly leaking air giving bad o2 readings made rich mix.
Still would like to verify mmHg pressure fuel tanks should read at different rpms if others have the info 2 share.

 

[Capt.Crunch]

I've been struggling with evap system problems & leaks for some time.
Replaced fuel pump 4 times as a couple purchased from Amazon for lower prices were wrong or inferior products, one had too many ports which plugged cap leaked then replaced with two port seemed good plastic swelled in fuel broke into pieces trying to remove from access hole now too small .
Current pump seemed ok still getting random air leaks & rich mix codes.
Anyone know live data pressure readings at idle supposed to be?
I've been seeing -1.482 mmHg?
Can anyone tell me correct fuel tank pressures?
I replaced gas caps three different types & drivers indicator sometimes says check gas cap sometimes.
I've checked all connections & replaced evap lines. Last effort soon is removing charcoal canister again & put new in and check if anything in tubes.
Some others say canisters can clog the evap tubes.
Which line usually gets canister gunk dumped/ plugged in?

Control circuit code was my testing x3 evap solenoids at fuel rail, all had seal no air leak. One made clicking noise loud like a lifter failing scared me. Found exaust nuts loosened some at cat/header joints possibly leaking air giving bad o2 readings made rich mix.
Still would like to verify mmHg pressure fuel tanks should read at different rpms if others have the info 2 share.

What year, and what trim package, Z71, LTZ, LT?

 

[Wpolonavyguy]

2007 5.3l LT 4x4, has 4in body lift, I replaced almost every sensor & turning out most troubles are seals & electrical.
Most recently I replaced exaust head gasket seals/ last time I found both sides rear most bolts sheared in block. I bought adapters both sides but stupidity used antisieze which allowed vibration untorque loosened leaks.
Cleaned & resealed exaust torqued using locktight liquid.
Intake manifold seal I did prior no sealant then had to redo second time using a non hardening gasket sealant with Intake gasket.
All 8 injectors are new lifetime warranty from Orilies auto parts, fuel pump seems ok now. Fuel pump I changed 3 times, cut access hole so don't need empty & drop tank to R&R.
Evap hoses new, have charcoal canister havnt changed for new as original wasn't bad.
Have x2 gastank purge solenoids and x3 of the fuel/rail purge solenoids all seem to be air tight with basic tests iv seen YouTube.
3 gas caps but thinking x2 aren't correct as advised by Amazon sellers.
O2 sensors newish, have new set if needed but believe catalytic converters bad over the sensors.
I'm soon going to take to a shop 4 help figuring what's still causing trouble.
Front wheel wells off & spare tire off to make easier viewing & accessibility to Evap & engine sides.

 

[Wpolonavyguy]

Filled tank & engine codes rich mix both banks cleared. Makes me think it's the fuel pump itself being submerged in fuel or not.
Hate to replace whole pump again, luckily cut access door under rear seat.
Anyone know why pump would cause rich mix when fuel levels are lower??
No fuel return line how does pump regulate pressure? I'm trying to figure reason gas submerging a part makes pump work correctly

 

[Wpolonavyguy]

Update, fuel level still not low enough to rule out pump or pressure regulator.
I did fix exaust leak that made computer #'s wrong.
I now realize the Avalanche probably didn't reset its fuel composition calculation after I repaired the exaust.
The bad fuel trims set codes resolved when I put 125$ gas into fuel tank.
Makes much more sense to me now as I don't think I disconnected battery because smog certification needed soon reset may take longer to complete drive cycles.
So far so good will know 4 sure if pump issue at 1/2 tank or lower. At least no dtcs I can try to get pass from Smog station.

 

[Wpolonavyguy]

So engine light comes back on at 3/4 gas level.
Had suspicion new evap hoses could possibly still leak air so precaution wrapped sylacone self adhesive tape around all connections I could with evap/canister.
Also melted beez wax poured around pump seal & electrical sensor areas to verify sealed.
I can only guess it's the fuel pump I purchased from Amazon not long ago having a pressure regulator issue.
Soaked in gas it's working as should but lower fuel level it causes rich mix both banks.
Taking to shop tomorrow to complete diagnosis to be sure. B4 i replace pump if not necessary.

 

[Wpolonavyguy]

Sylacone tape & conduit putty must have sealed the evap system enough. Just took a few additional startups to clear the engine light.
I'll definitely be keeping close watch on it, unfortunately I was impatient taped & sealed all so not sure which oring wasn't doing its job well enough.
If needby I can add Sylacone tape tighter & thicker one by one if issue returns.

 

[Wpolonavyguy]

Well seemed like problem may of fixed but code came back rich mixture bank 1&2... driving me crazy. Have thoughts was pump itself pressure regulator, now new code came up at 1/2 tank p0446 evap code.
I'll try testing vent & purge solenoids then maybe verify the fuel pump pressure sensor itself isn't sticking or faulty.

 

[Wpolonavyguy]

So I checked wires going to the purge solenoid at fuel rail, it's getting 13.83v looks like consistent from first starting truck. I didn't even get to plug up meter to activate it.
I saw it could likely be PCM problem but didn't exist until installed new fuel pump.
Anyone believe as I do fuel pump sending a bad signal to tell pcm to activate purge valve??
Purchased new pump already as I figured that was the change most recent.
Hate to send pump back & replace wrong part.