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Not sure what “weak evap” means.

In my experience, the O2 monitor sometimes takes a few days, or a couple of cold start/random driving cycles. The evap has never set in less than a week. My understanding is the evap won’t set until the others are ready, but I can’t point to a specific reason for that belief.

If they achieved readiness before, they should do it again. Give it a few more days.
 
FYI...There is a drive cycle procedure in case you interested in running it....
 
Well, no real updates. Still waiting on EVAP to set.

I did remove the big 'ol spot lights from the bumper and jack the front end up a foot and a half in the air on my driveway and put it through a few heat-cool(ish) cycles with the radiator filler funnel on. Got a few good burps out of it and it now seems to run and cool more along what I would expect. A trip up a local mountain road will tell more, but at least it seems to not need the fans while cruising on the freeway in 80* weather.
 
Finally burned enough gas that the EVAP monitor wants to run and it's still failing on the Weak Vacuum Test. Numbers have gotten (slightly) worse since last time it was run (14110 vs 14071 previously, fail is over 14000). Gonna have to crawl around and see what I can see.

I found this description of the EVAP test process from a PDF of the 2008 (ostensibly) Tahoe EVAP tests:

The purpose of the evaporative emission (EVAP) control system is to prevent the fuel vapors from escaping into the
atmosphere. The EVAP transfers the fuel vapor from the sealed fuel tank to an activated carbon, or charcoal, storage
device, or EVAP canister. The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor.
When the engine is able to use the extra fuel vapor, the intake air flow purges the fuel vapor from the carbon element,
and then the normal combustion process consumes the fuel vapor.
The system is designed to detect the evaporative fuel system leaks as small as 0.040 of an inch between the fuel filler
cap and the purge solenoid. The system can test the evaporative system integrity by applying a vacuum to the fuel tank
in order to create a small vacuum. The vehicle control module (VCM) then used the fuel tank pressure sensor to
determine system integrity.

Operation
The control module monitors the ability of the system to maintain the vacuum. If the vacuum remains for a specified
period of time, then there are no evaporative leaks, and a PASS report is made by the control module. If there is a leak,
the system either will not achieve a vacuum, or a vacuum cannot be maintained. Usually a fault can only be detected
after a cold start with a trip of sufficient length and driving conditions to run the needed tests. The enhanced
evaporative system diagnostic conducts up to 8 specific sub-tests in order to detect the fault conditions. If the
diagnostic fails a sub-test, the control module stores a diagnostic trouble code (DTC) in order to indicate the type of
fault detected.

Evaporative (EVAP) Emissions System Diagnostic Tests
The control module performs diagnostic tests in order to monitor the performance of the evaporative emissions (EVAP)
system. These test are as follows:

Excess Vacuum Tests
The control module monitors the fuel tank pressure (FTP) sensor signal during the normal purging of the EVAP
canister under various driving conditions in order to detect a malfunction in the fuel tank vent control components. If
the Excess Vacuum tests run and pass, the Purge Valve Leak Test will run. If the Excess Vacuum tests run and fail, a
DTC P0446 is set.​

Loaded Canister Test
The control module monitors the oxygen sensors during normal EVAP purging in order to determine if the EVAP
canister is storing a sufficient amount of fuel vapors. If the test indicates that the EVAP canister is storing a sufficient
amount of fuel vapors, the remaining diagnostic tests for the EVAP system will store a pass. If the Loaded Canister
Test indicates to the control module that an insufficient amount of fuel vapors are being stored by the EVAP canister,
the Weak Vacuum Tests will run.​

Weak Vacuum Tests
The Weak Vacuum Test is performed by the control module in order to determine if the EVAP control system is
capable of achieving a sufficient vacuum in the system. During the normal purging of the EVAP control system, the
control module will perform the following:
  • Command the EVAP vent valve ON or closed
  • Monitor the fuel tank pressure sensor signal
If the control module determines that sufficient vacuum is not achieved, the control module will perform the following
steps:
  • Store a DTC P0440 after the first failed test
  • Store the data in the Freeze Frame and Failure Records
  • Turn the malfunction indicator lamp (MIL) ON after a second consecutive failed test
If the control module determines that sufficient vacuum is achieved, the control module will perform the following
steps:
  • While the EVAP vent valve is ON or closed, turn the EVAP purge solenoid OFF or closed, and run the Small
  • EVAP Leak Test.
  • Run the Purge Solenoid Leak Test if the first Weak Vacuum Test passes.
  • Turn OFF the MIL, if the MIL is ON because of a previous failed Weak Vacuum Test.
  • Clear the data stored in the Freeze Frame for the DTC P0440.
  • The Weak Vacuum Tests will not run unless the Loaded Canister Test has run and failed.
Small EVAP Leak Test
The control module performs the Small EVAP Leak Test in order to detect a small leak in the following components of
the EVAP system:
  • The fuel tank
  • The fuel filler cap
  • The fuel filler neck
  • The EVAP canister
  • The EVAP vent valve
  • The EVAP vapor pipes and hoses
The Small EVAP Leak Test does not test the EVAP purge solenoid for leaks.

In order to run the Small EVAP Leak Test the control module performs the following steps:
  • Turn OFF the EVAP purge valve.
  • Following the passed Weak Vacuum Test and while the EVAP vent valve is still turned ON or closed, run the
Small EVAP Leak Test
  • Monitor the fuel tank pressure sensor signal.
The control module monitors the vacuum trapped in the system. If the control module detects an excessive decrease in
the vacuum that is trapped in the system, a DTC P0442 is set.

Purge Valve Leak test
The control module monitors the fuel tank pressure sensor signal during a cold start in order to test the EVAP purge
valve. With the purge valve OFF or closed, the VCM expects to detect no vacuum in the system. If the control module
detects a vacuum while the Purge Valve Leak Test is being performed, a DTC P1441 is set.​

Additionally, I found in another PDF the following codes and descriptions of the EVAP tests that you can reference against the above. Not all are applicable. (It looks like Tables are turned off in BBCODE? Please Forgive the formatting)
TID = Test ID (in HEX)
CID = Component ID (in HEX)
TLT = Test Limit Type

Enhanced Evaporative System Monitor #2 (0.020" Leak)
EVPD = Evap Vacuum Pressure Decay tests
EONV = Engine Off Natural Vacuum tests

TID CID TLT Description
0A 01 0-High EVAP/EVPD canister vent restriction test 1
0A 03 0-High EVPD weak vacuum test
0A 04 1-Low EVPD weak vacuum follow-up test
0A 05 0-High EVAP/EVPD 0.040" leak test
0A 06 0-High EVAP/EVPD 0.020" leak test
0A 07 1-Low EVPD purge pass test
0A 09 0-High EONV NV 0.020" test for EONV spec v22.0.0 and later
0A 0A 0-High EONV NV 0.020" test for EONV spec v22.1.1 and later
0A 0B 0-High EONV vacuum rezero test
0A 0C 0-High EONV fuel level rationality test
0A 0D 0-High EONV vacuum rationality test
0A 13 0-High EVAP weak vacuum test
0A 42 0-High EVPD canister vent restriction test 2 Out of range high
0A 42 1-Low EVPD canister vent restriction test 2 Out of range low
0A 48 0-High EVAP/EVPD purge vacuum fail test
0A 84 1-Low EVAP weak vacuum follow-up test
0A 87 1-Low EVAP purge pass test
0A C2 1-Low EVAP vent rest test 2
​

May whomever finds this post in desperate searches of the internet have less trouble than I did in finding it.
 
With that out of the way, given that TID 0A, CID 13 is showing as failing in the Mode 06 data on my reader, we are supposed to believe, as stated earlier, that the EVAP Weak Vacuum test is failing. Given it is trying to run the EVAP test at all, and not setting _any_ codes, we can probably (though, with my luck, errantly) assume the Fuel Tank Pressure sensor, and the Fuel Level Sensor are both feeding valid data to the ECU, even though I can't see it because it doesn't look like their PID's (either SAE or custom GM CAN) are turned on for reading on the ECU (#@$%@).

The EVAP Weak Vacuum Test only runs if the Loaded Canister Test fails, so the ECU thinks the Charcoal canister is not getting any fuel vapors and is trying to figure out why. If the Weak EVAP test fails (and mine seems to have done so, twice in the last two days) it's supposed to set a DTC 0440 and store frezeframe data. If it fails a second time, it's supposed to turn on the MIL.

The ECU has no stored or presented DTCs (pending or current DTCs), and has no freezeframe data stored, nor is the MIL coming on, however the ECU seems to be indicating this test is failing, so I am thoroughly confused.

_IF_ the test descriptions above are accurate, the test is failing, the computer doesn't care, and I have a leak somewhere between the fuel tank and it's atmospheric connections, right? Is that what I'm reading? So, the leak could be the filler neck, or a bad seal on any thru-hull fittings into the tank, or the tank itself, or one of the vapor hoses leading to the charcoal cannister, or between the charcoal canister and the engine? So nearly any connection not carrying liquid fuel? Does that seem right?
 
Question for those of you who have done and have a working swap, what does your fuel filler cap look like? My understanding is that the fuel system is supposed to be a sealed system now and no longer pressure vented to the atmosphere through the fuel cap like the old system. I have my old cap and made (meaning hacked out) a viton sheet gasket for it and put that over the top of what was there (images below) but I'm wondering what others have done? Maybe I'm leaking through the screw holes? Should I seal the thing up with some adhesive of some sort?

IMG_20190201_152553.webp


IMG_20190201_152538.webp


IMG_20190201_152538.webp


IMG_20190201_152553.webp


IMG_20190201_153052.webp
 
I would not think that cap is up to snuff for an OBDII evap system.

What fuel tank is in the truck? Have you ever replaced the sending unit seal? For that matter, you might take a look at how the sending unit was assembled and make sure it’s well sealed where the electrics pass through.
 
Allen, didn’t you say that the evap did come up ready before we re-flashed the PCM? If it did before, it should work again.

As I’ve said, it can take weeks for the evap to be ready. I know of a case where it took months. Maybe just needs a little more time.

BTW, I have a genuine Toyota filler cap. A little pricey, but I didn’t want to take any chances. Mine obviously seals adequately.
 
I think I have it figured, I just need to figure out time/how I'm going to fix.

Now that it's dry out, I crawled around under the truck in my driveway to tighten all the hose-clamps attached anywhere in the fuel system. I don't have a good pic of it, but I happened to pop my head up under the fuel filler to tighten the clamps on the filler hose leading in to the tank. There is hose leading from the filler to a free-floating u-shaped piece of steel tubing, then more hose from that piece of u-shaped tubing to the tank. At the input to that piece of tube, a rag has been wrapped around the tube and the hose placed over the rag-and-hose, I guess to stop a leak or try to adapt size between the two, and a hose clamp over that. I can't imagine in what world that would actually produce a good seal. It's probably leaking vacuum (and pressure) and may be a fire-hazard to boot.

Is there any reason the filler neck can't just be a piece of hose that runs from the filler inlet to the fuel tank inlet? Do I need this piece of u-shaped steel tubing for any reason? I don't see it at all in the FJ62 Fuel System parts diagram on SOR.

EDIT: in looking at the pics, it appears my view with the camera was better than with my eyes. It looks like the rag is just there to catch leaks. I think I'm just going to see about ripping the whole abomination out and replacing it with a single piece of hose, if that's not a dumb move?
 
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Pictures of this monstrosity in all its glory.

Edit: after spending more time under the tank and finding more hose clamps to tighten, I bonked my head on the frame and it occurred to me why the rag is there - the metal is right against the frame. Without it the thing would rattle like crazy.

1899032


1899033
 
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FJACS said:
I would not think that cap is up to snuff for an OBDII evap system.

What fuel tank is in the truck? Have you ever replaced the sending unit seal? For that matter, you might take a look at how the sending unit was assembled and make sure it’s well sealed where the electrics pass through.
Click to expand...

It's got an JF62 tank with a GM fuel sending unit. I haven't replace the sending unit, but it was installed with the tank after the swap. early 2016ish timeframe.
 
tmxmotorsports said:
Wow tor fab did this work? Talk to @NCFJ i am pretty sure he modified the 80 bigger tank to work with the 60 series body
Click to expand...

Not sure if left behind by Torfab or RSO. Brother, this whole thing has been both amazing and terrible.

The thing originally had a custom tank in it, but that's considered a fuel cell by CARB so it had to come out - hence the 60-series tank between the 80-series frame rails.
 
SPANNERSPINNER said:
Not sure if left behind by Torfab or RSO. Brother, this whole thing has been both amazing and terrible.

The thing originally had a custom tank in it, but that's considered a fuel cell by CARB so it had to come out - hence the 60-series tank between the 80-series frame rails.
Click to expand...

Wow is about all I can say! Do you know if this applies to MAF long range tank?
 
That stainless tube is because the 60 tank is moved back a certain amount? It looks horrible, and is that rubber hose attached to the tank kinked on the frame?
No, there’s no reason you can use a single hose, but I doubt you’ll find one that is long enough and has the bends in the right spot. On 2” hose like that it will kink if you try to bend it as you’ve witnessed on that frame rail.

I actually like the idea of stainless tube, I’d just go all the way from the 1/4 panel to just before the tank. Then a 2” long straight hose from the 1/4 panel to tube and a 90-degree pre-formed rubber hose from the tube to tank inlet, because it looks like the tank full I let is pointed right at the frame.
I don’t know what your fab skills are like but if that’s outside your capabilities and high-end exhaust shop should be able to make that for you with scrap mandrel bends no problem.
 
mig79 said:
Wow is about all I can say! Do you know if this applies to MAF long range tank?
Click to expand...

I'm not sure. If the tank is CARB approved and has an EO number, it's good. Otherwise, probably not okay in California.

@cruisermatt I didn't even think of hitting an exhaust shop for something like that but you're right.

Once I'm past BAR, the fuel tank will likely get replaced. I just need to get past BAR inspection and Smog. I'm thinking the hose being incredibly flexy and there being multiple segments might either be leaking vacuum or flexing enough under vacuum to mimic a leak. Not sure. Probably have more hose clamps to tighten. Need to open the hatch in the cargo area and check the top of the tank and the fittings.
 
In your first photo in 111 - what’s with the red AN fitting and the electrical tape wrapped around it? Is it a banjo wrapped tape?
 
Welp. This is officially flipping voodoo. I thought I kinda understood it, but now... Not much. That one test still registers as failing, but who the hell am I to question.

Time to see the BAR.

Screenshot_20190209-111533.webp
 
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