COMET CENTRAL

I have a question..... I'm having a fuel starvation problem, narrowed it down to fuel tank vent. my question , is the tank vented through the gas cap or does the tank have a plumbed vent? when I remove cap after driving its like under pressure. thanks guys....Ron

It should have a vented cap. but today's vented caps will let pressure build up but still can draw air in. kinda like a check valve. it is designed to not let any fumes escape,so pressure can build. so if you feel air releasing when you open it that would be normal.

Depends on year. Some have a vent and others dont. Look at it carefully for a vent. If none found then you need a vented cap.
Ron

[quote="Comechero65"]Depends on year. Some have a vent and others dont. Look at it carefully for a vent. If none found then you need a vented cap.
Ron[/quot

popscomet wrote:

Comechero65 wrote:Depends on year. Some have a vent and others dont. Look at it carefully for a vent. If none found then you need a vented cap.
Ron[/quot

POP was readin this and hit the wrong button....doesn't mean I agree with RON....I was not backing him up on his post,,I don't know what the man has..my 64 has a vent built into the filler neck.I believe...pop

Well it is in the 64-65 section ,65's didnt have a vented tank,they had a vented cap. I just assumed 64's were the same way since they have the same tank. but if Pop says his has a vent in the filler neck I believe him. But since the OP has a 65 it doesn't matter. It should have a vented cap [JMO !!!]

My 64 only had a vented cap no vent anywhere else.
I disliked the pressure build from the one way cap so I drilled a 1/8th inch hole right through the cap.
Fred

Fred said his has no vent only a vented cap. The 65 and I assume the 64 ranchero/wagon and sedan delivery didn't have a vent only a vented cap. I'm not surprised the comets were the same way. Fred jusr comfirmed his was the same. The early falcons up to through 63 did have a vent but ford eliminated it on the ranchero/wagon/sd in 64 and 65 since both years were a square body and had a larger tank that filled from the side.
When I moved my filler inside the bed I installed a vent tube from the top of the tank to the top of the filler neck. Installed another vent tube from the top of the filler neck down and out so no vented cap needed or used on mine.
Ron

poboyjo65 wrote:It should have a vented cap. but today's vented caps will let pressure build up but still can draw air in. kinda like a check valve. it is designed to not let any fumes escape,so pressure can build. so if you feel air releasing when you open it that would be normal.

Agree it should have vented, also think it should be anti surge, pretty sure mine was but been a long time since I looked at it.

The reason it should be anti surge is because of the location. When you fill the tank if you pull out hard the gas wants to exit thru the fill tube. Remember seeing people pull out from filling stations leaving a trail of fuel? Esp the ones with caps behind the lid plate? The anti surge keeps it from doing that. And it will build the pressure as you said.

Lou

hotrodron wrote:I have a question..... I'm having a fuel starvation problem, narrowed it down to fuel tank vent. my question , is the tank vented through the gas cap or does the tank have a plumbed vent? when I remove cap after driving its like under pressure. thanks guys....Ron

Loosen the cap and see if the problem goes away? If the problem goes away then replace it with a correct vented cap.

I see how a tank that doesn't have a vent or vented cap can have a fuel starvation problem. No air getting in to replace the gas leaving. But think of this. If you have pressure in the tank wouldn't that pressure help push the gas thru the lines??

Have you checked the sending unit in tank to see if it or the filter(if still there) are clogged?

Lou

POP was wrong !! my 64 has a vented cap also...reckon I was thinking about another old ford I have or one of my tractors.....that's the 2nd time I have been wrong this month....just plain brain fade OH WELL !! one thing about POP ....I will admit being wrong

Lou's Comet wrote:

hotrodron wrote:I have a question..... I'm having a fuel starvation problem, narrowed it down to fuel tank vent. my question , is the tank vented through the gas cap or does the tank have a plumbed vent? when I remove cap after driving its like under pressure. thanks guys....Ron

Loosen the cap and see if the problem goes away? If the problem goes away then replace it with a correct vented cap.
I see how a tank that doesn't have a vent or vented cap can have a fuel starvation problem. No air getting in to replace the gas leaving. But think of this. If you have pressure in the tank wouldn't that pressure help push the gas thru the lines??
Have you checked the sending unit in tank to see if it or the filter(if still there) are clogged?
Lou

You only get pressure in the tank if the fuel vaporizes faster then it is drawn out by the pump. But no guarentee of either condition at any given time so you can't count on it. If not and no vent then you get a vacuum. That's what makes it confusing on old cars is some got vents and others did not. A vented cap lets air in as fuel is used. Just doesn't let pressure out. I can see why Fred drilled a hole in his cap as insurance as then there will be no vac or pressure. Down here in calif the smog boys don't like anyone modifying anything but that's their problem.
Ron

hotrodron wrote:I have a question..... I'm having a fuel starvation problem, narrowed it down to fuel tank vent. my question , is the tank vented through the gas cap or does the tank have a plumbed vent? when I remove cap after driving its like under pressure. thanks guys....Ron

Ron...I'm confused about your symptoms and your cause. You say it's starving for fuel, and you've narrowed it to a fuel tank vent problem, yet the tank is under pressure. Seems to me that over pressurization might lead to flooding, but not starving. What makes you think the problem is with the fuel tank vent? Could there be a vapor lock situation going on instead?
Jim

Comechero65 wrote:

Lou's Comet wrote:

hotrodron wrote:I have a question..... I'm having a fuel starvation problem, narrowed it down to fuel tank vent. my question , is the tank vented through the gas cap or does the tank have a plumbed vent? when I remove cap after driving its like under pressure. thanks guys....Ron

Loosen the cap and see if the problem goes away? If the problem goes away then replace it with a correct vented cap.
I see how a tank that doesn't have a vent or vented cap can have a fuel starvation problem. No air getting in to replace the gas leaving. But think of this. If you have pressure in the tank wouldn't that pressure help push the gas thru the lines??
Have you checked the sending unit in tank to see if it or the filter(if still there) are clogged?
Lou

You only get pressure in the tank if the fuel vaporizes faster then it is drawn out by the pump. But no guarentee of either condition at any given time so you can't count on it. If not and no vent then you get a vacuum. That's what makes it confusing on old cars is some got vents and others did not. A vented cap lets air in as fuel is used. Just doesn't let pressure out. I can see why Fred drilled a hole in his cap as insurance as then there will be no vac or pressure. Down here in calif the smog boys don't like anyone modifying anything but that's their problem.
Ron

Sorry should have been more clear. My comment wasn't about how or why there is pressure. But more of a comment on when he removes the cap after driving he has pressure, and before a vented cap could restrict the fuel flow to the engine the pressure would have to be gone. The pressure would have to be down to zero before air even started getting sucked thru the vent.

Lou

Jims65cyclone wrote:

hotrodron wrote:I have a question..... I'm having a fuel starvation problem, narrowed it down to fuel tank vent. my question , is the tank vented through the gas cap or does the tank have a plumbed vent? when I remove cap after driving its like under pressure. thanks guys....Ron

Ron...I'm confused about your symptoms and your cause. You say it's starving for fuel, and you've narrowed it to a fuel tank vent problem, yet the tank is under pressure. Seems to me that over pressurization might lead to flooding, but not starving. What makes you think the problem is with the fuel tank vent? Could there be a vapor lock situation going on instead?
Jim

Was thinking the same. Maybe he instead of pressure he has a vacuum. It would make the same psssssst sound when removing the cap. But would be air entering tank instead of releasing from tank. Obviously one would make cap easy to take of and the other harder to take off but the difference may not be noticeable or small.

Easy way to see if vent is problem drive it with cap loose and see if problem goes away. On his 65 Cali there is the door to keep from loosing the cap..

Also curious to why he feels it is a fuel vent problem.

Lou