So I know this is probably one of those dumb questions and I did search before posting.....but..
Is there supposed to be pressure in the fuel tank on my 300SD?
When I open the fill cap there is quite a whoosh of pressure. Do I have a plugged vent line or is it supposed to be this way.

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Thanx,
Alberta Luthier
1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR

No, there should not be pressure in the tank. However, if your vent tube is blocked you should be hearing air rush in instead of rush out.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

It is definitely whooshing out. It actually sprays a bit of mist around the cap as I open it!

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Thanx,
Alberta Luthier
1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR

Hey another problem maybe they are related.
I think I have air leaking into the fuel system at the old style hand pump. The clear line up to the big filter has a lot of air rising with the fuel (none in the first filter) (and I have ordered a new style pump to replace it. Could running the engine be pumping this extra air back through the fuel return line? I need a good explanation of the whole fuel system. Anyone got a link? (I have searched)

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Thanx,
Alberta Luthier
1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR

What you say sounds resonable to me. But, is your car running OK with that air leak???
You will know when you replace the hand primer.
How old are the fuel hoses?

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84 300D, 82 Volvo 244Gl Diesel

okaaaay... weird is that my car did the exact same thing yesterday...
I got the fuel tank REALLLLLLLY low and when I went to the pump, the cap practally jumped out of my hand POW! very odd.
what could cause pressure?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Same Here (?)

(Here I go with Boogymen in the Tank,Again) Algae releasing gas as they expire?

Well....It has this low power problem at low rpms. very very low power but I took some slack out of the linkage and adjusted the alda a bit and it is better but sometimes it has ... well profoundly low power. Like, less than a 240D. Then as the turbo spools up very suddenly around 2000 rpms it pulls almost like it ought to and by 3000 it is pulling with all you could ask. I have tried the 'Italian tune up' a few times and it liked it I think. a couple of days ago I had an opportunity to really let her go. It was just before dawn and no traffic. I saw 3 cars in about 1 1/2 hours on a very good road that I know very well... 175 KPH wide open (109 mph) so I think it is fueling well at WOT.

__________________
Thanx,
Alberta Luthier
1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR

Yikes! This car was recently imported from Japan. A foreign strain of Pacific Rim Boogymen!!!

__________________
Thanx,
Alberta Luthier
1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR

So have you had algae do this? Was it plugging up your fuel filters? My first filter looks new. And it fuels well at WOT even when the tank is down to near 1/4. And the low power thing only happens at low to mid rpm. Now if I had a fuel restriction I would expect the low power thing to be the other way around.

__________________
Thanx,
Alberta Luthier
1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR

My tank has air escape when I poen it and it has had that since I bought it. I don't know what it would be but my tank is very clean so it's not algae.....On a side note wouldn't positive pressure help the fuel pump a little bit?

The kinda shows the vent opening, near left rear wheel, make sure it is unobstructed.

Attached Thumbnails

 

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83 SD

84 CD

hey guys......Elegant Madame did it. Coda is doing it too. I crawled under her the other night, found the tank vent, took the think off....could not get a wire pushed up there more than 3 inches. So. I got the air hose and blew a lot of air up there......with the tank cap OFF, of course.

There is something else going on.......is there a "check" valve at the top of the vent? Maybe it is stuck closed?

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daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

hmmm just a thought, but since the fuel system is closed loop except for the vent to allow for pressure equalization as the tank level goes down, in other words, lets air in... if it was very cold in the morning, and you drove, cold dense air would get in the tank, then as it got warm in the area, that cold air warmed up and built up pressure? possible it's just a spring weather thing?

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Running the engine warms the fuel.

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Gone to the dark side

- Jeff