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Gas caps, Vented or Non-Vented

6K views 26 replies 8 participants last post by  SoCalChlln 
#1 · (Edited)
I have been recently having a problem with a P1441 code being thrown and my CEL coming on.
I inspected my gas cap, and I pushed and released the push button vent on it several times before trying to blow air past it.
It seemed to be air tight.
I have replaced all the rubber vacuum lines to and from the new Genuine ACDelco OEM switch and new OEM vacuum control, then checked again for any other potential leaks in the system.
The other day I purchased a new Duralast Non-Vented gas cap.
Thinking I would avoid any future issues with the push button vapor release not holding pressure.
My CEL came on again today after about 50 miles, the code, the same P1441 (vapor flow during non-purge event)...
When I opened the cap, I did hear the rush of vapor coming from my filler tube this morning, after the CEL had come back on..

Is the cap on a 96 Impala SS supposed to be vented or non-vented ?

Am I experiencing a situation where as the fuel is being consumed, a vacuum is being created in my tank and the EVAP system seeing the low or loss of pressure as a vapor flow during non purge event, hence the DTC ?
Or do I need to drop my fuel tank and check the lines going into it?
I can’t think of any other component areas where there could be a possible pressure leak releasing the fuel vapors into the air.

Any suggestions ?
Any and all help is greatly appreciated!
Thank You for your time !!!
 
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#2 ·
The evap solenoid and canister are in the engine compartment. Could be leaking there. Not sure if the cap is supposed to be vented or not. I know that on a warm day if I open it I can hear the pressure releasing.
 
#3 ·
Lotsa terms involved with the EVAP system being mentioned which I believe is the right track for tank pressure/suction issues. But not catching any chatter on rebuilding the charcoal can - or redoing all the nasty slimy old collapsing eaten hoses hiding under the headlight and battery. On the vented-nonvented thing, I'd just make sure to replace the cap with an oem whatever type it is.
 
#13 ·
Is there a way of rebuilding the canister (Properly) ?
I know it’s got activated charcoal in it but I don’t know if it can be refreshed/rebuilt, or if I should just buy a new one.
I don’t want anything done that is anything less than the best I can do for the car, saving money is a concern, but doing a professional grade repair/replacement job is more important to me...
Thank You for the advice and information !
 
#4 ·
Believe it is non-vented with a pressure/vacuum relief valve that opens at some point as a fail safe.
 
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#9 ·
I purchased a Duralast non vented last week since the ACDelco one was not in stock. I was concerned about a vacuum being created in the tank as the fuel is consumed, but I don’t think it is a real concern.
I could be wrong, but I intend to replace the cap with the ACDelco when it comes in anyway so we’ll see how it goes until then.
Thank you for your response and time !
 
#5 ·
#6 · (Edited)
Or do I need to drop my fuel tank and check the lines going into it?
!
No, you do not have to drop the gas tank to access (inspect) fuel lines and vent line coming out of tank. See the pictures in this nice post:
https://www.impalassforum.com/vBull...holding-pressure-help-suggestions-needed.html

Gas vapors eat up rubber hoses. The disconnected (rotten) hose in the pictures goes to EVAP in engine compartment.
Thank you for the excellent advice and link to the pics, those are very helpful.
I will locate everything I can under the car tomorrow and replace every vacuum line and worn rubber hose there is to replace. As it just happens, I was under there a few days ago refilling my Diff after changing Gear Lube. I probably bumped it and cracked it without noticing. I'm gonna bet that's the culprit since it started happening again the following day...
I am the kind of person where if I’m working on something,
I keep my eyes peeled for anything that looks less than perfect, and replace any parts that need it. I also am going to deal with this EVAP system with new hoses everywhere, as I’ve already done the switch, control valve, the electrical connectors, all vacuum lines reachable from top of the engine compartment, and the gas cap...
Once one thing starts to go wrong with a system. I believe in replacing everything associated with that system back to a like new state.
I hate roadside problems.
Thank you again for the response !
 
#7 ·
Thank you everyone for all the excellent advice and information!
As well as for your time and effort.
I believe I found the ‘main’ culprit, the rubber jumper from the tank to the nylon line going forward.
I am still going to get at the canister to replace it and all hose lines attached or associated to it...
At that point I will have in essence a completely new EVAP system operating in my car.
 

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#8 ·
Next time I drop the fuel tank I will also replace the filler hose and the breather tube at the rear of the fuel tank. The filler hose I can replace without dropping the tank so I might do it now also, but the breather tube goes into the fuel pump access so it can only be done with the tank dropped, or the magic hole cut into the trunk of my car.
I’m still considering whether to do that or not.
Any comments on cutting the hole ?
All advice is appreciated !
Thank You...
 
#10 ·
Researched cutting hole for FP access...
The overall general advice is not to do it on B Bodies, it requires a rather large hole to be cut, takes out your spare tire mount, and is way more work than dropping the tank on a B Body Impala.
I’ve dropped my (empty) tank before, it’s not that bad...
But it is the only way to replace the rear breather hose...
 
#16 ·
David, I have been working on my garage today and then had to cook and take dinner to my mother in law. Her sister, who's in the hospital wanted a milk shake. So I was gone for a bit. I got back and there were several posts on your thread here. If I had seen it earlier I would have voiced my opinion FWIW. The cutting of the trunk for access to the sending unit has come up more than once in the past. I can't say about the canister rebuild. Mine's different than yours. I guess if it can be opened, without breaking it, maybe there is a chance to replace the charcoal. Understand I have two old ladies and one mean Beach to take care of. We all live in the same block. It takes a lot of my time.
Best of luck,

Mark: Snowman-33
 
#17 ·
My friend...
I hope I didn’t give you the impression I was in any way disappointed or expecting you to answer in anything but your own good time, I would NEVER expect that if anyone here on the forums.
I’m totally thankful for the spare time you’ve already contributed to helping me. I’m thankful you offer your help at all.
As you know my daughter is in the hospital also so I completely understand, never feel bad or think I would ever want you to neglect any aspect of your life on my account.
When I don’t hear from you fairly quickly I know it’s because you’re doing much more important things.
Just as I am sometimes these days.
Best wishes of a full and speedy recovery for you MIL’s sister...
And for your rest and peace of mind...
 
#18 ·
David, It never crossed my mind. Sometimes things get discomboobulated online. I try to understand. I read earlier about your daughter. My best to her and pray for her recovery. Unfortunately my wife's aunt's is terminal. She's 85 so she's had her life. MIL is 86. Friday night I found out my very good friend and former LE partner fell and broke his hip. He has ALS. I'm trying to stay in there. Getting old is not for the young. Once again we digress. Forum please forgive us.

Mark: snowman-33
 
#20 ·
Bob's on target again. One thing came to mind though and it might not be a big deal. Since California is so anal about things involving the emissions. I would make a cut that could be covered by the EVAP canister bracket. It may not be anything but then again. I learned long ago to make a plan and then what if it.

Mark: Snowman-33
 
#21 · (Edited)
Unless the technician wants to remove my air dam, and the inner bottom bumper plate, he won’t be able to even see the canister.
I’m my impala it’s underneath the battery tray and is visually inaccessible by any other means.
I put all new rubber going to the canister yesterday, new rubber coming from tank forward to the nylon line. There’s only two more places I can have a vapor leak.
Is there a rubber hose connector in the front of the nylon line that runs the length of the car from tank to EVAP up front, like the one going into the fuel tank ? There must be, since both lines to canister were metal. Does anyone know where the front nylon line connects to the EVAP system ?
The damn CEL light came on again today after close to 75 miles without it coming on after I replaced all the rubber to the canister.
Thank you for any information, and any time spent responding,
I’m becoming a little more than frustrated here.
 
#22 · (Edited)
Do you have a FSM? It is excellent on this subject. There are 2 hoses connected to nothing.

Section 6E3-C3-3
 
#23 · (Edited)
I’m still throwing p1441 codes every morning when I take my car out for the first drive of the day.
Can a bad canister cause this ?
I would think the canister would have to have a small leak in it somewhere that drops my tank pressure to zero overnight for it to throw the CEL on.
I was under the impression there are no valves or anything in the canister. Just 3 holes that connect to three different sized fuel lines.
But can the canister become old and wear out.
I’ve NEVER smelled the odor of gasoline in my garage before, which from what I’m told is the indicator it’s time to replace it.

I intend to replace it anyway but I want to get this p1441 code to stop first.
Thank you for any and all suggestions and help !!!
Can the canister cause a flow during non purge event code ?
Thank you all for the time, energy and help.
 
#24 ·
I may have missed this in the thread, but you also have to make sure the diaphragm valve by the cannister is working, along with the purge valve on the pass side of the intake manifold. The purge valve is prone to clogging or failure, and the 3-inch S-shaped hose connected to it cracks over time. Check yours and see.

The hose pn is ACDelco 12556259. I have an extra hose still in the unopened ACD baggie that I'll put in the mail for free if you need it. Just send a PM and you can have it.
Mark
 
#26 ·
Thank you for the response Mark !
As usual accurate, informative and easily understood...
PM sent...
I have changed out every rubber hose in the system except the filler hose and vent hose that goes up into the back of the gas tank filler tube. Including the ‘S’ shaped one between the switch and valve. That was one of the first ones to get changed while I was putting in the new switch and valve.
The filler hose I can replace easily enough but it looks as though it’s been replaced at some point,and is in good shape. The 3/4” vent hose I would have to drop the tank to replace. I may end up doing just that though to check the fuel pump seal at the same time.
I put in all 3 new EVAP control components, the switch, the control valve, and the canister valve.
I have not put in a new canister as I didn’t think it would cause the p1441 code.
Is that a false assumption ?
Can the canister cause the pressure to leak down. I suppose it could have a crack in it somewhere I didn’t see while replacing those hoses and the valve, but the canister doesn’t even pressurize does it ?
It’s maddening, it’s a slow leak somewhere because if I clear the code, do a drive cycle and drive around several times during the day it stays off.
When I start the car, warm it up, and drive it first time of the day, the CEL comes on as soon as I hit 25 - 30 mph...
I’m thinking of doing a smoke test on the damn system, a friend has a compressor, an empty metal paint can and tapped gas cap connected together whereby you put baby oil on a rag, light it on fire, put it in the paint can, close the lid to snuff the flames and produce smoke, which is forced into the system pressurizing it, then look for smoke leaks.
If anyone had a better method I would love to hear about it. I’ve considered using one of those red little round smoke bombs in the paint can instead of baby oil and rag, but I also don’t want to contaminate the valves and switches I just replaced.
Thank you for the advice and help Mark!
I always appreciate it even if I’ve done it. (It at least confirms I’m doing it the right or wrong way)...
I’ll continue with this until I get it straightened out...
Or I’ll just lay down in the back seat with all my tools, light the car on fire, and go out like my Viking ancestors did...
LTKFC... (Lauging To Keep From Crying)...
Thank you for all you effort Mark !
You’ve been great about it !!!
David...
 
#25 · (Edited)
The rubber hose connecting the tank to that nylon tube was off for years but I never had any EVAP codes. Go figure...

Here is an extended discussion of P1441 code (which may make you sick...).
https://www.troublecodes.net/p1codes/p1441/
BTW, it is always a current code, right? The system stores fault codes (history) for certain number of ignicion cycles.
 
#27 ·
Thank you very much for the link !
It was very helpful in understanding not just what the system consists of, but what all the components do, and how to check them for function.
I will be holding onto this bookmark, and referencing it in any of the future events whenever a p1441 code is thrown...
Thank you very much !
 
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