Difficulty pumping gas at the gas pump

Tiny
TOOKIEN
  • MEMBER
  • 2007 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
When pumping gas at the gas pump it takes a really long time as it is constantly clicking/shutting off.

The gas does not spill out or anything it just constantly clicks off.

I already did the following:

- Replaced the purge and vent solenoids
- Replaced gas cap
- Replaced the charcoal canister
- Disconnected all the vent/EVAP lines and blew compressed air. Confirmed that none of the lines are clogged (air comes in and out normally). Including at the filler neck.
- Confirmed filler neck hose is not clogged or bent.
- Confirmed vent at filler neck is not clogged.
- I can also hear the compressed air entering the gas tank unrestricted.

After I disconnected the lines, blew compressed air through all of them.
I went to the gas pump and could pump gas normally for a certain period of time then it started clicking again. Problem then came back full-time.

It seems the vapors are not being purged properly.

I have a check engine light EVAP code that comes up PO466 from time to time (I am not sure if it is related at all as this code has come up in the past but I did not have issues at the gas pump).

I am going to perform some more tests on the (brand new) purge and vent solenoids to make sure they work.

Other than that, what could the problem be?

Could the gas pump issue be related to the fuel tank pressure sensor, or some electrical issue (I do not see a fuse for the EVAP system).

And my OBD scanner is limited when it comes to checking live data.

Please help. Thank you
Thursday, November 1st, 2018 AT 10:26 PM

7 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 46,965 POSTS
The only item that stops the fuel from entering the gas tank is the filler neck with its external vent. Can you tell me how you know the filler neck is okay? Here are diagrams to help us see what we are talking about. When the neck of off check to see if there is a roll over ball stuck in the fill of the tank. I would remove the filler neck to inspect.

Check out the diagrams (below). Please let us know what you find.

Cheers, Ken
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Sunday, November 4th, 2018 AT 11:04 AM
Tiny
TOOKIEN
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Thank you Ken. Appreciate the response.

One thing I have not done is inspect the filler neck by removing it.
I will do that when I have the chance and will definitely update here on the result.

That maybe the problem after all and it should have been the first thing I check.

Thank you again.
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Sunday, November 4th, 2018 AT 5:03 PM
Tiny
KEN L
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No problem we are here to help. Please let me know what you find. :) Ken
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Monday, November 5th, 2018 AT 8:53 AM
Tiny
TOOKIEN
  • MEMBER
  • 20 POSTS
Hi Ken,

The problem actually resolved itself, at least temporarily for the past week now. No more check engine light, no more PO446 code, no more difficulty pumping gas. My theory is that there is some issue with the fuel pressure sensor circuit or some other electrical issue in the EVAP system. So I think it is safe to say it is not the filler neck (I Have not had time to inspect it yet).
Thank you again for the help!
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Monday, December 3rd, 2018 AT 2:58 PM
Tiny
KEN L
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I think it is the filler neck, there is nothing else that can cause the problem.
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Monday, December 3rd, 2018 AT 6:45 PM
Tiny
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Hi Ken,
If the problem returns, I will simply change the filler neck and update here again. Thank you!
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Monday, December 3rd, 2018 AT 9:11 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 46,965 POSTS
Sounds good. Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers, Ken
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Tuesday, December 4th, 2018 AT 10:50 AM

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