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Old 01-02-2020, 01:10 PM   #1
jamesfacts
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Thumbs down 04 WRX gas tank does not pressurize, P1446

Hi all,

I'm working on with a swapped GC with 04 WRX everything—ECM, gas tank, evap system, engine, everything. The only GC component that might be relevant is the filler neck, which I'm using with the 04 "shut valve", the little two-way port with a brass button that sits toward the gas cap.

I cannot get the system to pressurize and it is driving me crazy. When I open the gas cap, there's no difference from the ambient pressure, no "whoosh" from the seal opening. I do have a code 1446 "Fuel Tank Sensor Control Valve Circuit Low". No other codes. I believe this is caused by the actual low pressure in the tank, not a fault in the circuit or the sensor. There is definitely a mechanical condition that's not right so my approach has been to try and correct that condition first.

I have disassembled, cleaned, bench tested and replaced nearly the entire system. Here's what I've tried so far:

* Smoke tested evap / charcoal canister for leaks
* Replaced entire gas tank, with lines, float, sensor, and VSV
* Bench tested drain valve
* Smoke tested purge line running to the fuel rail, replaced purge valve itself
* Tested wiring running from the ECM to fuel tank harness, I don't see any shorts and the ground signals from the various gas tank sensors are all continuous to the ECM.
* Tested signal from the internal fuel pressure sensor to the ECM while the car is running. According to AllData, the ECM wants to see more than 10.9v from the pressure sensor. I get ~12.4v sent back to the ECM.

I am totally stumped what could be going on here. The fuel / evap system is not that complicated... what could possibly cause a tank not to hold pressure? I did reuse the seal from the fuel pump cage to the tank but I have never seen those leak so badly that the tank wouldn't pressurize. What else can I try next to diagnose and correct this issue?

Edit, here's the page from the service manual I've been working off:

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Last edited by jamesfacts; 05-18-2020 at 04:19 PM.
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Old 01-09-2020, 09:56 AM   #2
FierceWRX
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Default evap

First of all, there should be no pressure in the system unless it is very hot causing the fuel to expand, like on a 90 degree day. Evap systems check by applying vacuum via purge valve to the fuel tank and close the vent valve. It then expects to see vacuum on the sensor. To check it, you need to smoke test at the test port or purge valve and actuate the vent valve so it seals. look for smoke with a bright white light.
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Old 04-17-2020, 01:04 PM   #3
geekbstrd
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Default p1446

jamesfacts, Did you find a resolution to this problem? I seem to have a similar problem.
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Old 04-17-2020, 02:05 PM   #4
TXwrxWagon
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I chased EVap & tank related problems for nearly 2 years... cannot count how many times I replaced almost everything...

I did get the 1445 code once along with a punch of other codes that were all EVAP related.

Mine turned out to be a fuel saturated charcoal canister. The canister should feel light in weight when picked up. IF it has a heavy/dense feel to it, then the tank/canister were "topped off" while filling an fuel got into the canister itself.

2 easy tests:

1. remove the canister and hold it in your hand or actually weight it, it shouldn't be more than a pound or so

2. turn the inlet/outlet ports 90* to the ground, if fuel comes out there is a problem, even if little charcoal pellets fall out, canister needs replaced.

If the canister is contaminated, it will drive the engine mounted purge solenoid and the rear evap purge solenoid bonkers.

So far for quality EVAP parts rockauto has been the best value.

Lastly check all the EVAP hoses and especially the fill-neck to tank hoses. I had a fine tear in my neck2-tank coupler and found that the worm-gear clamps had punctured the rubber allowing a leak.

~Rob
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Old 04-17-2020, 06:15 PM   #5
geekbstrd
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Default Thanks

Thanks for the reply, I will keep digging away at it.
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Old 05-17-2020, 06:11 PM   #6
jamesfacts
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Quote:
Originally Posted by geekbstrd View Post
jamesfacts, Did you find a resolution to this problem? I seem to have a similar problem.
Sorry to have neglected this thread for so long! Quick update... no, I never figured it out. I do have a few ideas moving forward but no time to try them yet.

Quote:
Originally Posted by FierceWRX View Post
First of all, there should be no pressure in the system unless it is very hot causing the fuel to expand, like on a 90 degree day. Evap systems check by applying vacuum via purge valve to the fuel tank and close the vent valve. It then expects to see vacuum on the sensor. To check it, you need to smoke test at the test port or purge valve and actuate the vent valve so it seals. look for smoke with a bright white light.
I did test much of the system with a smoke machine but I wasn't 100% clear on what valves I ought to expect to be normally closed and which ones are open at rest. I tested the system in stages because the volume wasn't sufficient to quickly fill the entire evap system. Now I'm thinking I will retest with a hand vacuum pump, since any loss of vacuum should immediately reveal a leak. It's my understanding that the system should be entirely closed at rest from the purge valve back.

Interestingly, I do notice the idle stumble just a hair when the underhood purge valve is activated. That suggests to me that there is a leak somewhere in the evap system... or it could be a perfectly normal drop in intake manifold pressure as a result of the volume of the evap lines?

Quote:
Originally Posted by TXwrxWagon View Post
I chased EVap & tank related problems for nearly 2 years... cannot count how many times I replaced almost everything...

I did get the 1445 code once along with a punch of other codes that were all EVAP related.

Mine turned out to be a fuel saturated charcoal canister. The canister should feel light in weight when picked up. IF it has a heavy/dense feel to it, then the tank/canister were "topped off" while filling an fuel got into the canister itself.

2 easy tests:

1. remove the canister and hold it in your hand or actually weight it, it shouldn't be more than a pound or so

2. turn the inlet/outlet ports 90* to the ground, if fuel comes out there is a problem, even if little charcoal pellets fall out, canister needs replaced.

If the canister is contaminated, it will drive the engine mounted purge solenoid and the rear evap purge solenoid bonkers.

So far for quality EVAP parts rockauto has been the best value.

Lastly check all the EVAP hoses and especially the fill-neck to tank hoses. I had a fine tear in my neck2-tank coupler and found that the worm-gear clamps had punctured the rubber allowing a leak.

~Rob
Thanks so much for chiming in, Rob! Your thread was one of the most helpful ones. I found. My charcoal canister is original (2004 WRX original, not 98 RS original) but the weight appears in spec and I couldn't find any leaks. Do you have any idea how exactly the ECU is upset by a contaminated charcoal canister?

What an incredibly complex set of vac lines and solenoids back there huh

Quote:
Originally Posted by geekbstrd View Post
Thanks for the reply, I will keep digging away at it.
Good luck! Please do post here if and when you figure it out.
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Old 05-17-2020, 07:42 PM   #7
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When you smoke tested it where was smoke coming from?
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Old 05-17-2020, 09:45 PM   #8
08SpecB_DE
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You can pinch or block off the vent hose, otherwise you would need a powerprobe and a wiring diagram to apply power and/or ground to the vent valve to seal the system prior to smoking it.
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Old 05-18-2020, 04:36 PM   #9
jamesfacts
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Edited the original post to include the FSM diagram.

Quote:
Originally Posted by alejandrochilds View Post
When you smoke tested it where was smoke coming from?
It seemed like the system was fairly airtight, but I never tested from the charcoal canister (#6 ) forward. I capped the lines from the charcoal canister to the drain valve (#8) since I think that's open? I also think from 7 to to 10 is normally open?

I also never smoke tested with the tank in the test circuit because I figured it would take too long to fill the whole tank with smoke.

The more I think about it now... I think the better way to pressure test the evap system is to pull vacuum on the purge line under the hood with a hand vac pump. At rest the entire system should be air tight (from the purge valve line), right?

Quote:
Originally Posted by 08SpecB_DE View Post
You can pinch or block off the vent hose, otherwise you would need a powerprobe and a wiring diagram to apply power and/or ground to the vent valve to seal the system prior to smoking it.
I've been using wooden dowels inside of rubber caps to cap the system section by section. Which direction would you test from?
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Old 05-18-2020, 08:35 PM   #10
08SpecB_DE
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From the purge line that goes to the tank. I'm not sure what kind of machine you're using, but it does take a couple minutes for it to fill the system. Does it have a gauge to show leak size? (i.e. .0020, .0030, etc) The professional machines say anything under .0020 is acceptable but I've found that not to be true. The system is sealed when that little pill flat lines. When you're filling it with smoke, remove the gas cap. When the smoke starts coming out, obviously put the cap back on, but it's an indication that its filling up and should be pretty full throughout.
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Old 05-18-2020, 08:38 PM   #11
08SpecB_DE
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https://forums.nasioc.com/forums/showthread.php?t=1183535

Could this pertain to you?
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Old 05-21-2020, 03:07 PM   #12
jamesfacts
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Quote:
Originally Posted by 08SpecB_DE View Post
From the purge line that goes to the tank. I'm not sure what kind of machine you're using, but it does take a couple minutes for it to fill the system. Does it have a gauge to show leak size? (i.e. .0020, .0030, etc) The professional machines say anything under .0020 is acceptable but I've found that not to be true. The system is sealed when that little pill flat lines. When you're filling it with smoke, remove the gas cap. When the smoke starts coming out, obviously put the cap back on, but it's an indication that its filling up and should be pretty full throughout.
ahh, that's good to know. I did not use the gas cap trick. Totally possible I was not running the smoke tester properly.

This is the machine I used: https://www.ebay.com/itm/Redline-Det...t/362703747933

I can probably go borrow it again.

Quote:
Originally Posted by 08SpecB_DE View Post
https://forums.nasioc.com/forums/showthread.php?t=1183535

Could this pertain to you?
It could... but I would rather fix the actual issue. I had previously set 1446 to permanently "not ready" with an ECU flash but the tank wasn't pressurized then either so something was definitely not right.
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Old 05-21-2020, 10:08 PM   #13
08SpecB_DE
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May be a dumb question, but did you have it hooked up to an air compressor? If you pinch or cap off the vent hose and smoke it through that purge line that runs to the back of the car, the little pill should flat line if there are no leaks. This does not confirm if a valve or solenoid is working properly but you'll be able to rule out rusty lines, fuel pump seal, filler neck and gas cap.
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Old 05-26-2020, 10:09 PM   #14
jamesfacts
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Quote:
Originally Posted by 08SpecB_DE View Post
May be a dumb question, but did you have it hooked up to an air compressor? If you pinch or cap off the vent hose and smoke it through that purge line that runs to the back of the car, the little pill should flat line if there are no leaks. This does not confirm if a valve or solenoid is working properly but you'll be able to rule out rusty lines, fuel pump seal, filler neck and gas cap.
Yep, hooked up to an air compressor! I had the entire system out of the car (separate from the smoke test!) and I inspected it closely. No damage, rust, worn seals to the naked eye. I'm going to give pressure testing another go with the hand vac
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Old 05-26-2020, 11:06 PM   #15
08SpecB_DE
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To each their own. I've never used a vac pump to check for leaks but there's more than 1 way to skin a cat. Good luck!
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Old 06-01-2020, 03:22 PM   #16
jamesfacts
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Quote:
Originally Posted by 08SpecB_DE View Post
To each their own. I've never used a vac pump to check for leaks but there's more than 1 way to skin a cat. Good luck!
So, I had some time to test the system this weekend and I think I was able to identify an issue. I used one of these pumps:
https://www.skf.com/mityvac/products...leeding/mv8020

First, I capped off the purge line running to under the hood, to reduce the volume of air I would need to pull vac on. I did test the line itself and it does hold pressure.

Then, I tested the system in chunks, working from the charcoal canister. I capped the two big lines running out of the charcoal canister and verified that the canister itself is air tight. Then I tried to pull vac on the tank itself, working from this line here:



The gas tank did hold pressure, so then I moved on to the other big line from the canister, the one that runs to the drain valve. That line does not hold vacuum. My understanding is that the drain valve should stay closed at rest, right? I know it does open sometimes to vent the canister to atmo, but I'm not sure what triggers it to open.

Here's the only thing I could find in the FSM on the drain valve:



So, two questions:

Should the drain valve be normally closed? Is it an issue that it's open to the atmosphere at rest?

Can I safely cap the line to the drain valve and test if that makes the CEL go away?

Thanks!
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Old 06-02-2020, 11:45 PM   #17
AliBenn
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Hey y’all
Me and James be both struggling with our own CC8 swap issues
Been rapping about both owners issues......for months!
IMO
James’ issue more technical
Mainly bc of CA emission laws
Did you know that if you bring in a swapped car, inspection technician busts out a book with pictures of said manufacture’s engine bay? Then your screwed
James had perfectly running (no CE lite what so ever) swapped GC8
So in a nutshell
He learned that if you do have a swapped car, EVERYTHING must be swapped
Including in this case, fuel tank ‘system’
This is mandatory to get registered in CA
Crazy Crap
Then this obd2 code popped up

So here is my 2cents
Plz y’all, James more technical about stuff like this
Critiquing my opinion encouraged !!!
1) if J caps off the hose, might work
However, might also be noticed by the CA Nazi inspectors
That might be BAD
2)I said to take off that valve....clean tht thing with brake cleaner/MAF cleaner whatever
Then test continuity on said valve. Bc 2wire system
J told me that white valve is $80
NP throwing parts at the issue.....if you know issue or your rich

I’m really hoping that plastic valve is stuck one way bc car came from NE

Help my friend and crush my crappy theory!!!!
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Old 06-02-2020, 11:50 PM   #18
AliBenn
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BTW James
If my cam seals leak again after my 6th T belt RI
Will send you the new short Block.
Of course you have to come to TX to take out motor!!!!!!
����������������������
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Old 06-03-2020, 10:41 AM   #19
subaru_gc8
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Quote:
Originally Posted by AliBenn View Post
Hey y’all
Me and James be both struggling with our own CC8 swap issues
Been rapping about both owners issues......for months!
IMO
James’ issue more technical
Mainly bc of CA emission laws
Did you know that if you bring in a swapped car, inspection technician busts out a book with pictures of said manufacture’s engine bay? Then your screwed
James had perfectly running (no CE lite what so ever) swapped GC8
So in a nutshell
He learned that if you do have a swapped car, EVERYTHING must be swapped
Including in this case, fuel tank ‘system’
This is mandatory to get registered in CA
Crazy Crap
Then this obd2 code popped up

So here is my 2cents
Plz y’all, James more technical about stuff like this
Critiquing my opinion encouraged !!!
1) if J caps off the hose, might work
However, might also be noticed by the CA Nazi inspectors
That might be BAD
2)I said to take off that valve....clean tht thing with brake cleaner/MAF cleaner whatever
Then test continuity on said valve. Bc 2wire system
J told me that white valve is $80
NP throwing parts at the issue.....if you know issue or your rich

I’m really hoping that plastic valve is stuck one way bc car came from NE

Help my friend and crush my crappy theory!!!!
yep california emmsions sucks the big one. its super hard and only getting harder to get passed this stuff
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Old 06-03-2020, 09:52 PM   #20
jamesfacts
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Quote:
Originally Posted by 08SpecB_DE View Post
To each their own. I've never used a vac pump to check for leaks but there's more than 1 way to skin a cat. Good luck!
Quote:
Originally Posted by AliBenn View Post
Hey y’all
Me and James be both struggling with our own CC8 swap issues
Been rapping about both owners issues......for months!
IMO
James’ issue more technical
Mainly bc of CA emission laws
Did you know that if you bring in a swapped car, inspection technician busts out a book with pictures of said manufacture’s engine bay? Then your screwed
James had perfectly running (no CE lite what so ever) swapped GC8
So in a nutshell
He learned that if you do have a swapped car, EVERYTHING must be swapped
Including in this case, fuel tank ‘system’
This is mandatory to get registered in CA
Crazy Crap
Then this obd2 code popped up

So here is my 2cents
Plz y’all, James more technical about stuff like this
Critiquing my opinion encouraged !!!
1) if J caps off the hose, might work
However, might also be noticed by the CA Nazi inspectors
That might be BAD
2)I said to take off that valve....clean tht thing with brake cleaner/MAF cleaner whatever
Then test continuity on said valve. Bc 2wire system
J told me that white valve is $80
NP throwing parts at the issue.....if you know issue or your rich

I’m really hoping that plastic valve is stuck one way bc car came from NE

Help my friend and crush my crappy theory!!!!
Quote:
Originally Posted by AliBenn View Post
BTW James
If my cam seals leak again after my 6th T belt RI
Will send you the new short Block.
Of course you have to come to TX to take out motor!!!!!!
hahah, thanks buddy! I appreciate all your brainstorming and I hope your theory tests out 100%!

Quote:
Originally Posted by subaru_gc8 View Post
yep california emmsions sucks the big one. its super hard and only getting harder to get passed this stuff
sure is... but at the same time something is really broken and I do want to fix it!
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Old 06-09-2020, 11:43 PM   #21
AliBenn
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Update Homie?
Bump
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Old 06-10-2020, 02:32 PM   #22
jamesfacts
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Quote:
Originally Posted by AliBenn View Post
Update Homie?
Bump
I actually started a new thread with just my v specific question!
https://forums.nasioc.com/forums/sho....php?t=2922790

I took the old valve out and it seems like it's in fine working order, but I did order a new one just for fun.
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Old 06-16-2020, 01:14 AM   #23
jamesfacts
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Well for everyone holding their breath at home, my new valve arrived and it works exactly the same as the old one. The drain valve appears to be normally open at rest.



Scratching my head thinking about where to go next.
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