Bad gas cap or Purge Solenoid?

[Mike534x]

Hi everyone back with another problem this time. Got a message on my DIC about 3 weeks ago saying I need to tighten my gas cap, after doing some searching and calling a few dealerships they said it was the gas cap. We'll I bought a new AC Delco gas cap from rockauto and changed out the old one. Fast forward a week later and the message is back again, there is no CEL light, however hooking up the code reader shows a P0455. I tried clearing that code after changing out the cap and its back.

Could I have gotten a fault new gas cap or am I looking at possibly replacing the purge solenoid?

 

[Mooseman]

Possible but not likely. Leak could be anything.

Possible causes Missing or loose fuel cap Incorrect fuel filler cap used Fuel filler cap remains open or fails to close Foreign matter caught in fuel filler cap EVAP canister or fuel tank leaks EVAP system hose leaking Fuel tank leaking

You almost need a smoke machine to find it.

 

[Mike534x]

Thanks Mooseman, is the smoke machine something auto shops like Advanced rent out?

I don't smell gas, so I don't think its the tank leaking. So that leaves the canister or the hose leaking then.

I was thinking of trying the purge valve(AC-Delco #214-1680) since its cheap enough.

 

[mrrsm]

@Mike534x... A word of caution...

Occasionally... some Genius will attempt to "Blow Out the Evap System" with compressed air without realizing that what is ordinarily a "Fuel Vapor Saturated Closed System" should NEVER have an atmosphere of any kind introduced that contains any Oxygen. The risk of an explosion from an errant spark might make things a bit too exciting... if you catch my drift.

These are all the possible issues that might be involved and the "Evap Purge Solenoid" is usually the main culprit due to its constant use to bring fuel vapors back down the line and inside of the Charcoal Cannister
.
http://www.engine-codes.com/P0455.html

If you feel creative and want to use compressed gas of an Inert Flavor... You can purchase non-refillable containers of Dry Nitrogen for around $25.00 to experiment with. Youtube also has a rash of videos worth watching about all problems encountered with The Evap Systems and from a generic perspective... they will show you what these guys do while crawling around under the GM Vehicles. :>)

 

[Mike534x]

@MRRSM Thanks! I'll have to take a look at the Dry Nitrogen, its cheaper then dropping $120 or so on a Smoke Machine!

As for the Purge Solenoid, would that be the Purge Valve on the engine block or the Canister that's near the gas tank?

 

[mrrsm]

For all the trouble you'd go through trying to "Smoke Out" the leak or problems... while this is definitely a "No-No" around here among GMT Nation Folks who are reluctant to just throw parts at a problem... My guess is that the "Under the Vehicle" Purge Solenoid is is the probable culprit. However since its relative sits right on top and in front with easy access for this R&R... you would not lose too much Time & Money by replacing it as well. These two videos cover both topics very nicely... Especially the First One:

Brian from Briansmobile1 Youtube Channel shows how to work on and test the Charcoal Cannister Evap Solenoid if THIS component turns out to be The Bad Part in the Evap Leak issue:

Alternatively ...Way Up Front and On Top of the Engine is THIS one that is the EASY ONE to work on:

 

[Mike534x]

Excellent! Thanks for the links! I ended up ordering both the Purge Valve and Vent Valve, didn't pay out of pocket thanks to a gift card.

It looks like they changed the location of the Purge Valve on the 05 model year, it looks like it sits/attaches to the drivers side fuel rail above the ignition coils.

 

[littleblazer]

Just an fyi, on our envoy the tank pressure sensor was ultimately what died causing our p0455. Just another thing to check.

 

[Mike534x]

I'll add it on there as well, I'm hoping the Purge Valve takes care of the issue. Is the tank pressure sensor the one that sits at the top of the tank, or on the side? If its on the side, that saves the hassle of dropping the tank.

Back to the Purge Valve real quick, is it necessary to order the bracket Part Number #12579283 that Rock Auto suggests or would it just hook right up like the current one?

 

[Mike534x]

Quick update: Going onto a week now with the new Purge Valve in, so far, I haven't had the gas cap message pop up in the DIC. Code Reader doesn't show any pending EVAP codes either, going to give it a bit more time just to be on the safe side.

 

[Mike534x]

Well I spoke too soon, got in this morning and the CEL came on. Ran a scan with the code reader and it's coming up as a P0449.

Would this be related to the canister/vent solenoid near the gas tank?

 

[Mooseman]

I would think so. This code is an actual malfunction of the valve or circuit itself and not a leak this time.

 

[Mike534x]

Ah alright. Well the P0455 with tighten fuel cap is back....ugh...I guess this leaves the canister now?

 

[mrrsm]

Mike ...

Take whatever Tool(s) that will work to undo and then re-tighten the Rubber Filler Neck Hose between the inside attachment points at the under frame filler neck and also at the place where the hose attaches to the Gas tank and loosen both connections completely. Then...without imparting too much force... attempt to rotate the hose back and forth while the two connection points remain in place...kind of like rolling it around on bearings...and then return the hose to its original position and re-apply the clamps. Then clear the codes and take it for a Test Ride to see if the loss of pressure occurs again.

 

[Mike534x]

Mike ...

Take whatever Tool(s) that will work to undo and then re-tighten the Rubber Filler Neck Hose between the inside attachment points at the under frame filler neck and also at the place where the hose attaches to the Gas tank and loosen both connections completely. Then...without imparting too much force... attempt to rotate the hose back and forth while the two connection points remain in place...kind of like rolling it around on bearings...and then return the hose to its original position and re-apply the clamps. Then clear the codes and take it for a Test Ride to see if the loss of pressure occurs again.

I'll give it a shot, we're going to put the canister in this weekend and we'll loosen the hose and try rotating it a few times. Hopefully that clears it up! Could it just be dirt/grim/etc just building up along the inside part and its just enough to lift the seal enough to make it appear as a leak?

 

[mrrsm]

Automotive Themodynamics Play Hell on components in all vehicles... From Bumper to Bumper and on everything in between. This is compounded by the reality that Plastic and Rubber hosing and Metal Tubing expand and contract at very different rates over uncountable heating and cooling cycles that have a tendency to move everything around quite a bit... no matter how well they were secured on the factory floor during their initial assembly, long... long ago.

So it should come as no surprise that while dealing with the passage of Cold Fuel coming down that pipe innumerable times... that the hose and clamps could change their positions over time. This just happens to be the last place that we would ordinarily look for any leaks or loss of vapor containment issues... and since you have exhausted the Major Component R&Rs ... it can't hurt to take a look at that hose down there and see What's What. ;-)

 

[Mike534x]

Ah! Alright, well there really isn't much to lose at this point. I can see that causing some sort of leak, so I'll definitely mess around with it and see where it gets me. Don't really know what else that could be causing an issue, otherwise the only thing left to replace would be the Fuel Tank Pressure Sensor, but that seems to be a different code all of its own. It's actually interesting that I had the first code pop up back in January, it went away for a few weeks and now its back again. It was pretty cold, and now that its been heating up and cooling down like clockwork, then maybe it could be something simple like the filler neck needing a "reset".

Would the Engine Coolant Sensor, play a part in setting a false code perhaps?

 

[mrrsm]

@littleblazer gave you the Dope and suggested replacing the Fuel Tank Pressure Sensor above at Post Message #8... So if the "Lefty-Loosey-Righty-Tighty" Actions with the Fuel Filler Hose and Clamps don't solve the problem... review his data for the help as your next Port of Call.

 

[littleblazer]

I'll add it on there as well, I'm hoping the Purge Valve takes care of the issue. Is the tank pressure sensor the one that sits at the top of the tank, or on the side? If its on the side, that saves the hassle of dropping the tank.

Back to the Purge Valve real quick, is it necessary to order the bracket Part Number #12579283 that Rock Auto suggests or would it just hook right up like the current one?

The sensor depending on year is on the back of the tank just past the filler neck or on the top by the pump. I forget if they switched in 05 but if it's on the back it isn't bad to do without dropping the tank. I ohmed mine out and it gave a wacky reading compared to what I thought it should be.

Edit: did you happen to look up in the scanners section if there is someone near you with one? I feel like this could be helpful instead of just throwing parts.

 

[Mike534x]

Scanner? Like a tech 2?

I'll take a peak at the back of the tank to see if I can find the location of the sensor, I think I recall seeing something with a connector running to whatever is in that area. So the tank sensor can set of that code? That's so bizarre, but I guess when it comes to this platform anything is possible. If the filler neck and canister doesn't help, then the fuel tank sensor it is.

 

[mrrsm]

The "Scanner Section" @littleblazer referred to is on the Main Menu Page and has Five Sub-Sections for you to browse around on the topic:

 

[Mike534x]

Oh! I completely missed that.

Well I got in the truck this morning, the gas cap message didn't appear in the DIC and the code "vanished" from the system, even though it showed it active when I checked with Torque last night. Managed to get under there and swap the canister out, the old one had cracks (also made a small rattling noise inside when shaken) along where one of the hoses run to the connector which I assume is a vacuum line of some sort? I have the pictures attached below of what it looked like. The only thing I didn't do was loosen the filler hose and give it a twist, after seeing the cracks in the canister before even removing it from its mount. If it pops up again, I'll be under there to loosen it and give it a twist here and there. The Tank Pressure Sensor is still in the location @littleblazer mentioned, near the rear top half adjacent to the canister. Unfortunately for me I may have to drop the tank some, my hands are a little too big to squeeze into that confined space.

 

[Mooseman]

Those cracks are bad. Never seen that on a canister before. I think you found the culprit.

 

[Mike534x]

@Mooseman So far after driving it around a bit, all seems good. I'm giving it another week to see what happens, with it being warm in a few days, this should help in determining if it was fixed since it seemed to pop up during the times the temperature was changing. Here's to hoping this was the culprit! I wonder what could have caused it?