Fuel vented/ nonvented catastrophe

[rabbithunter2005]

So I parked my 69 F100 back on nov. 27 of 2020 for the winter. Just curious if anyone has ever had this catastrophe happen. I had half a tank of gas in it when I parked it. Well I tried starting it here and there and it wouldnt crank hardly at all. I even got a breaker bar out and it barely wanted to turn but then it would free up. I would crank it with the starter again it would go half a turn then lock again. So I kinda put it on the back burner focused on a 351c im building for my highboy. Well one day I come out to the garage happen to look under my truck and I have a brownish puddle and im talking huge puddle. I crawl under it and see its coming out of the front of the oil pan. I dip my finger in it and it reeks of gasoline. Now things add up. I go back to the truck and crack my gas cap loose and pressure city. Now this is supposed to be a vented cap I got from rock auto obviously not if I have that much pressure to push fuel past the needles in the carb and fill up the cylinders with gas. I now have a quarter tank of gas and I didnt even get to burn any of it actually driving. Does anyone know where I can find a factory vented gas cap cause this is the second supposed vented cap ive bought and no matter what I end up with a pressurized tank. I never had this problem with my factory cap but I don't got it no more cause my girlfriend doesn't know how to put a gas cap on properly so it fell off going down the road last summer.

[pcmdub]

Vented Gas cap lets air IN not OUT.

[basketcase0302]

I seem to remember there is even a difference in the fuel fill pipe/tube in the bumps, (from the early to the later 70'-72') due to emissions. I constantly had issues with fuel caps too on BC #16, (71' model) and more than once had a cap venting then on any given day it would crap out my issues would start. Mine always seemed to favor destroying the paint on the outside of the truck below the gas fill, (like many stories here you'll read about).
Can suggest trying to find an OEM for the 69' that specifies "vented".
It's not a Cali' bump is it? I also remember some discussion about a few extra emissions parts on the Cali' bumps to look for.

But I'd also look very close at your fuel pump! I've seen more than one vehicle, (not just a Ford specific issue) with oil in the crankcase due to a busted fuel pump diaphram. Had a buddy with an early 70's C series chebby that drove it like that for days, (against better adivce that you're basically driving a bomb around with gas in the crankcase)!

[ddcrim]

You could just drill a hole in the cap.

[Lee]

You could just drill a hole in the cap.

Would be worried about rain water getting into the tank.

[rabbithunter2005]

Mine isn't a california bump and I know what your saying about it going the other way around with fuel running out and around the cap and destroying paint on the cab my highboy does that if I fill it up too high. This is not a fuel pump issue tho I just replaced it a year ago for having a broken diaphram and I honestly wouldnt doubt that this was a contributing factor but soon as i loosened the cap up the leak out the oil pan stopped which tells me it was the pressure in the tank pushing the fuel thru the needles in the carb then the carb overflowed drained into the intake and gas filled up which ever cylinders had an open valve. I got her running again changed the oil and cranked it for a bit with the msd disconnected so I could pump any gas out of the cylinders so hopefully I wouldnt mess anything up all that really did was pump it into the mufflers tho. Shoulda heard the gunshot out the tailpipes when it did fire up. Had all the neighbors outside wondering where the shots were fired . But yeah all good for the time being just gotta remember to loosen my cap when I park it til I can get ahold of a 71 or 72 tank that has the vent tube on the tank. I need a new tank anyway this one has some rust in it.

[basketcase0302]

Try doing the same thing, (pulling all 8 plugs/unhook ignition/cranking engine over/squirting gas for 20' out of each cylinder of a swamp buggy 30 miles from the nearest pay phone LOL)!!!

Sold my Holley carbs after that and never bought another, (bad...reputation and my personal expierence with the secondaries "bounding and getting stuck open) both vacuum and mechanical type. Love...dem...Motorcraft 2150 2BL's!

Glad you avoided a possible disaster!