2005 Subaru Outback 2.5i base A/T. 100% Arizona car, zero rust or corrosion on anything, 182,000 miles. This car is my unicorn, I’d drive it to the moon and back tomorrow.
I have built many engines in my day, very competent with modern vehicles and have always done the work myself except for tire swaps and alignments. I am not a beginner and generally do not have issues I can’t figure out, however the issue below is STUMPING me so far.
About 1.5 years ago, my fuel tank stopped venting at the gas station while pumping and I could only pump roughly .5 gallon at a time as pressure built up. The issue went away for 1 week and returned to its current state for the past 1 year. Over the past year, the issue has been the same, extremely consistent. Pump in .5 gallon, wait about 5 seconds to hear the pressure equalize through the filler neck, and repeat.
- No CEL’s
- No pressure/vacuum when unscrewing gas cap in any scenario
- No change at dozens of pumps at dozens of gas stations
I decided to finally rip this thing apart so I printed all the fuel tank diagrams and started from the end of the system, the vent to atmosphere.
- I took every hose from the vent to atmosphere back through the charcoal canister and to the vent nipple on the top rear of the driver side of the tank and blew through them, including the canister. Zero obstructions, completely free flowing.
- I disconnected the tank to canister hose and went to get fuel. Same issue, while pumping, NO air/fumes are coming out of the vent nipple on the tank. For giggles, I blew on the vent line INTO the tank and it was completely free flowing OUT the filler neck. All of the ~3/4” vent line from the tank to the atmosphere are completely free of obstruction, as is the canister.
- I then went to the filler neck side, pulled the filler neck and found it to be completely clear of obstruction. The mechanical valve on the top of the filler neck is working as it should via the flapper. This time though, I pressurized the filler neck with air to simulate filling the tank with liquid fuel. The only place that is venting ANY air/fumes from the tank is via the hose that goes to the TOP of the filler neck.
Does anyone know why there is no venting out of the ~3/4” VENT nipple/hoses into the charcoal canister?
Does anyone know why the only venting that is occurring is routing to the TOP of the filler neck?
I am clearly missing something and would happily call myself stupid and enjoy it being something dumb, but I am temporarily at a loss.
Thanks in advance everyone!! I am going on a 6000 mile road trip starting in July and would love to fix this by that time as that is a lot of fill-ups!
Appreciate the read and your help would be greatly appreciated!