P0455 again....Can't fill gas tank

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97camaroSS e30 318is Spicy #1348
I have pulled every hose back around the filler tubes. When inspecting the CdCv I was able to get air to go in both directions? Should this be closed one way when the car is off? Haven't tested it, but I imagine that it would cause a large leak detection if it's always open and should be closed during operation. Still doesn't explain why I can't put gas into it if it were open not impeding air flow.

My check valve was fine. Air went in both directions but vacuum showed a closed path in one direction, no debris.

The filter canister was almost dry. It barely gave a few drops with air blown in repeated times.

The hose going to the charcoal canister didn't allow air in. When I blew into it, the air came back, slow hissing. I did that a few times and got a few drops of gas?

Any ideas?

The car runs fine. No noticeable drop in mpg. The gas fill up issue is very annoying.
 

pcb

The Diagram Dude
:
2002 MP5
I've got a 2002 P5 and I don't know if your car is different.

There is a fuel shut off valve inside the gas tank.
It could be stuck shut.

There is also an anti-flow back valve in the filler neck that could be broken/jammed. I remember one guy that said he simply removed it and he could fill his car again.











As far as I understand it, when you're filling your car, the air rushes out from the gas tank through part #2 then through #3, #4, #5, #6, #7 then up to the filler neck where it blows on the fuel pump handle to keep the gas flowing.

I figure you should be able to blow air freely from hose "A" right through the system.

Remove the filler cap to allow the air to escape so you know your not pressurizing the tank instead of the lines if there's a blockage and it blows back at you.

If it doesn't flow, try disconnecting the hose going from the CDCV to the fuel shutoff valve and try to blow through that one.

If it were me and the fuel shut off valve appears jammed shut, I would blow compressed air through it to try to unjam it.

Replacing a fuel tank is an expensive, dangerous PITA.

There is also a code for the CDCV that should cover it if it's stuck, as well as various EVAP codes.

I've had the code for the CDCV valve and replaced it and I've also replaced my gas tank because it rusted out.

I haven't verified about blowing through the entire venting system with my DD though, so I'm still guessing.

EDIT: I forgot about the two-way check valve.
You may not be able to blow air through tube "A" but you should be able to suck air through it.

But that might give you brain damage. Lol

Maybe from just after the two-way check valve.
 

pcb

The Diagram Dude
:
2002 MP5
I just noticed your code in your title. Lol

As far as I know, the CDCV directs the air rushing out of your gas tank during filling up to the vent tube but will vent to the atmosphere when the ignition is on.

I don't know if my CDCV valve was sticking open or closed when I got my code (it was ten years ago and a mechanic did it), but I had no problems filling my tank.

I suppose I could try to gas up with the ignition on to see what happens?

I don't know if the car needs to be running but that's kinda illegal. Lol

You can also do a smoke test and there is a procedure to go through to get some valve to close.

I'm thinking putting power to your CDCV valve to test it would be a good idea.
 

pcb

The Diagram Dude
:
2002 MP5
I just found your other thread about your issue. (I thought I remembered it?)

It sounds like you've covered everything except the fuel shut off valve inside the tank.

The FSM says to remove the fuel tank to test it but that's a big PITA.

I'm pretty sure you should be able to blow through that vent line freely as long as your tank isn't full closing the valve.
 
:
97camaroSS e30 318is Spicy #1348
I haven't replaced the cdcv yet. I'm gonna try the car on with fill up. Does the car have to be running or can the ignition just be on?
 

pcb

The Diagram Dude
:
2002 MP5
I'm not sure.
Plus your car is already not filling properly, so if your CDCV valve is stuck causing the issue then the ignition on or off probably wouldn't make a difference.

It would be my car that fills properly where leaving the ignition on may put the CDCV in the wrong mode and maybe prevent filling?

The CDCV valve is quite accessible and easy to remove.
You could remove it and apply 12 V to it and listen for the click and try blowing through it with and without the 12 V applied.








I'm kinda thinking your fuel shut valve in the fuel tank is stuck closed.

The ECU only tests the EVAP system when the fuel level is between 35%-85%.

By the time the fuel level drops to 85%, the fuel shut off valve should have opened up.
I'm almost positive that it is a float valve and air should flow both ways through it when it is open.


This is a thread about the CDCV valve which might be helpful.




This is your code.
It can be a large leak or blockage.











And there's this too.






 
Last edited:

pcb

The Diagram Dude
:
2002 MP5
After thinking about it some more, I think my CDCV valve was stuck open.

That's why my car would allow gas into the tank. The air rushing out of the gas tank during filling goes through the valve and ends up blowing on the pump nozzle.

If your valve is stuck closed the air can't blow through the valve to get to the pump nozzle.

I'm almost positive there would be no power to the CDCV with the car off or it would drain the battery over time so it should be open with the car turned off and closed with the car running

If your valve is stuck closed, it would be seen by the ECU as a blockage.

If your CDCV valve is working properly then I figure your fuel shut off valve in the tank is stuck closed.

That would suck because you would need a new fuel tank.
 

pcb

The Diagram Dude
:
2002 MP5
I was curious so I hacked my fuel shut off valve out of my old gas tank.

It's been sitting empty and open for two years so I used a grinder to attack it.





Oops, I sprung a leak. Lol




I figure it must be the shut-off valve because it's got the big vent tube going to it.

The rollover valve has smaller tubing.
 

pcb

The Diagram Dude
:
2002 MP5
Well, there it is all apart...

It's kinda complicated actually.
Maybe so it can deal with gas sloshing around in the tank?


 

pcb

The Diagram Dude
:
2002 MP5
Does the car have to be running or can the ignition just be on?
I found this...
Its a code for a bad circuit for the CDCV valve.

It looks like the CDCV valve is turned on as soon as the key is turned to on.



I don't get that code though. It doesn't turn on the CEL and there is no freeze frame data and it doesn't store the code.

So how do you even know if you throw that code?
 
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