# Fuel in EVAP vent line P0451 very low tank pressure **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** gmc\ **Created:** [January 11, 2025, 3:57pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670 "2025-01-11T15:57:12Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [January 13, 2025, 9:00pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/21 "2025-01-13T21:00:31Z")
If you have a bidirectional scanning tool, you may be able to close the vent solenoid and open (set the pulse rate) the purge solenoid while watching the FTP value…The last time I checked my TB, the FTP wasn’t exactly zero when vented… ---
**Author:** ![Rainflurry](https://avatars.discourse-cdn.com/v4/letter/r/cab0a1/32.png) [@Rainflurry](https://community.cartalk.com/u/Rainflurry)\ **Post date:** [January 13, 2025, 10:26pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/22 "2025-01-13T22:26:48Z")
> [@PaintPaint](#): > > Just stating that key in or out, engine running or not pressure is the same 10-4. Thanks for clarifying. ---
**Author:** ![PaintPaint](https://avatars.discourse-cdn.com/v4/letter/p/eb9ed0/32.png) [@PaintPaint](https://community.cartalk.com/u/PaintPaint)\ **Post date:** [January 19, 2025, 2:24pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/23 "2025-01-19T14:24:18Z")
Got the tank dropped. Cleaned out the inside and replaced the fuel pump which includes the new FTP sensor. Cleared out all the vent lines including checking the one in the tank and the vent line to the filler neck. FTP sensor was shot as the readings now work however it still difficult to fill the tank. I can fill slowly but the pump clicks off if i get even close to normal speed. Only thing i can think of is that the vent to fill neck or the vent valve are not free flowing enough. Any help appriciated. ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [January 19, 2025, 2:39pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/24 "2025-01-19T14:39:40Z")
My vue has trouble starting after fueling. IF I gas up with motor running I have no issues. With key off, nothing is energized and fuel goes where it shouldn’t. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [January 19, 2025, 2:43pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/25 "2025-01-19T14:43:52Z")
> [@PaintPaint](#): > > I can fill slowly but the pump clicks off if i get even close to normal speed. Worst case, remove the filler neck and stick a garden hose in it and see how it flows, make sure there is not a restriction in it… ---
**Author:** ![PaintPaint](https://avatars.discourse-cdn.com/v4/letter/p/eb9ed0/32.png) [@PaintPaint](https://community.cartalk.com/u/PaintPaint)\ **Post date:** [January 19, 2025, 8:54pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/26 "2025-01-19T20:54:21Z")
OK so i took a garden hose and stuck it in about the same distance as a fuel nozzle. After a few min of full blast no issue with water flow into the tank but now the truck wont start. What now? ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [January 19, 2025, 8:57pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/27 "2025-01-19T20:57:14Z")
Are you saying you actually put water in the fuel tank ? If no wonder it won’t start. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [January 19, 2025, 10:54pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/28 "2025-01-19T22:54:36Z")
> [@PaintPaint](#): > > OK so i took a garden hose and stuck it in about the same distance as a fuel nozzle. After a few min of full blast no issue with water flow into the tank but now the truck wont start. What now? Ummm, I said remove the filler neck… Did you remove the filler neck from the vehicle before you ran water through it??? ---
**Author:** ![PvtPublic](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/pvtpublic/32/13089_2.png) [@PvtPublic](https://community.cartalk.com/u/PvtPublic)\ **Post date:** [January 20, 2025, 8:14am UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/29 "2025-01-20T08:14:58Z")
> [@PaintPaint](#): > > After a few min of full blast no issue with water flow into the tank but now the truck wont start. What now? > [@VOLVO-V70](#): > > Are you saying you actually put water in the fuel tank ? Now you have it hauled to a real shop. You will obviously not solve this problem. ---
**Author:** ![PaintPaint](https://avatars.discourse-cdn.com/v4/letter/p/eb9ed0/32.png) [@PaintPaint](https://community.cartalk.com/u/PaintPaint)\ **Post date:** [January 20, 2025, 11:48am UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/30 "2025-01-20T11:48:48Z")
All joking aside, I can get a 1/2" OD tube about four feet down the fill tube so I dont think its obstructed. I also can free pour gas from a 5 gal can without issue. I could just start re-replacing the vent, purge, etc but im getting tired of crawling under the truck. Also its still puking gas into the vent lines. ---
**Author:** ![PaintPaint](https://avatars.discourse-cdn.com/v4/letter/p/eb9ed0/32.png) [@PaintPaint](https://community.cartalk.com/u/PaintPaint)\ **Post date:** [January 21, 2025, 4:27pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/31 "2025-01-21T16:27:10Z")
I re-replaced the vent valve last night and now the truck is taking gas at full speed. The ‘old’ vent was an autoparts brand, not even a year old, and was testing open with no power. The new vent is OE from RA. No clue if the old valve is testing open why it would cause the issue. It was also nice and clean on the inside with no indication of a fault. Maybe I’ll eat crow in about a week when the truck throws another fit. Ill also have to wait for better weather to see if there is still gas in the vent lines. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [January 21, 2025, 4:40pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/32 "2025-01-21T16:40:14Z")
Thanks for the update, glad it is working so far… I recommend NOT marking it as the solution until proven it is taken care of for a month… lol… just incase… it happens… ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [January 21, 2025, 10:43pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/33 "2025-01-21T22:43:35Z")
> [@PaintPaint](#): > > I re-replaced the vent valve last night and now the truck is taking gas at full speed. Good for you. I expect your fix will do the job I’m just a knucklehead diy’er offering opinions, but my understanding is that for vehicles like yours (having a modern evap system), when the gas tank is being refilled the air/fuel vapors inside the tank has to have somewhere to go, otherwise that space becomes pressurized and this reduces the flow rate for the rest of the incoming gasoline. The normal path for those air/fuel vapors to go is through the vent valve to the charcoal canister, where the fuel & air separate, the fuel stays inside the cannister, and the remaining fuel-cleaned air is discharged into the atmosphere. ---
**Author:** ![PaintPaint](https://avatars.discourse-cdn.com/v4/letter/p/eb9ed0/32.png) [@PaintPaint](https://community.cartalk.com/u/PaintPaint)\ **Post date:** [February 1, 2025, 1:49pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/34 "2025-02-01T13:49:04Z")
I cant mark a solution because it was multi-tiered -Fuel Tank Pressure Sensor was dead. Replaced the entire fuel pump module which included FTPS. -Cleaned out carbon rat turds from fuel tank and roll over valves on top of tank. Manually cleaned inside of tank. Just pushed/pulled air through roll over / vent valves to make sure they were open with fuel pump out. One valve or connection on top of the tank at the rear and the other connects to the fuel pump and routes somewhere to the inside front of the tank. -Re-RE-replaced a seemingly working Evap Vent Valve. Even though the old one tested open when off. Truck has now been able to take 1/2 a tank of gas twice full speed from half to full and only clicked off once. Was able to complete at full speed. No CEL (YET) Hasnt run .020" Evap test yet but has passed 0.090", purge tests, etc Evap pressure showing movement and values as it should ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [February 1, 2025, 2:54pm UTC](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670/35 "2025-02-01T14:54:01Z")
Thanks for the update, No solution needed, maybe go back and edit your last post and add at the top of it in bold as the solution to easily be seen better… [Previous page](https://community.cartalk.com/t/fuel-in-evap-vent-line-p0451-very-low-tank-pressure/198670.md?page=1)