How is the fuel tank vented

[palmtree]

I seem to be getting some sort of vacuum in my fuel system. I was having trouble starting it and so I installed a bulb style hand pump and some clear lines so I could see what is going on. If I have someone crank it over while I pump the bulb it will start and run. Then when I shut it down I can barely hear the squeak of some air getting in and will slowly see bubbles forming in the clear fuel line. If I try to start it without someone pumping the bulb then I can see the bubbles just sitting in the line. Fuel doesn't seem to move (I assume it is air locked).
I can't tell how the tank is vented. I have a hose that runs from up near the filler neck and hangs down open near the tank. Should the open end of this line be attached to the tank somewhere?
Any ideas?

[ngoma]

What kind of vehicle?

[palmtree]

Originally Posted by ngoma

What kind of vehicle?

Oh, sorry. It's a 1980 265 with d24.

[v8volvo]

IIRC the 700 series diesel cars have an open tank vent with some type of rollover valve that closes the vent if the car ends up with the wheels in the air.

Do you see or smell any evidence of fuel leakage around the back of the engine? This sounds a little like a leaky injection pump driveshaft seal.

[palmtree]

Thanks for the info. It's a 1980 265. I don't see any fuel leaks. It's funny sometimes when I pump the hand bulb I can hear the air expelling into the tank (bubbling) and then when the air is out I am no longer able to pump the bulb. It's driving me crazy how I can hear the very faint squeak of air after depressing the bulb but I can't tell exactly where it is coming from.

[ngoma]

Try it with the fuel fill cap off (fuel tank completely vented)-- does it do the same thing?

[RedArrow]

Originally Posted by v8volvo

IIRC the 700 series diesel cars have an open tank vent with some type of rollover valve that closes the vent if the car ends up with the wheels in the air.

V8volvo, I can confirm that this is very true bc I worked on the 740 while the car was upside down. There was no fuel leaking from the tank or anywhere. It was very hard work to try removing the fuel filler assembly that way, and I was ready to take a shower in diesel fuel but it never came.