I went to fill up today and when I opened the tank cap a big push of air came out at me. The cap had a good amount of pressure.

Tank was at the 1/4 mark. I have had some push of air before but not like this. Car is a 85sd
Idea's anyone?
Thx
greazer2b

A small amount of pressure is Normal. Could be a plugged fuel tank filter..

Quite possible your tank vent is clogged.

Under the drivers rear door you'll see a bell shaped item, this is the vent, carefully snake a coat hang wire up through it.

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83 SD

84 CD

Thanks for the info but I have never seen that tube before when under the car.
I will check under tomorrow if we don't get ice storm they are perdicting.
I do have a 85sd so that picture is for that car?
Thx,
greazer2b

Straight out of the FSM.

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83 SD

84 CD

Are you sure it's pressure and not vacuum you are hearing? Next time you open the cap, put your face close to it and see if you feel a puff of air. If not, it's vacuum and the vent under the car is clogged.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

It's pressure and I not one for putting face in there. When I released the cap it pushed into my fingers and the air blew up my long sleeve shirt.

I have haven't looked under the car yet but plan too, I will be installing a replacement set of axels with in the week so I will have plenty of time then.
Thx for your input.
greazer2b

OK so it is pressure, which is not normal. Normal should be vacuum if you have a clogged tank vent. As the fuel is consumed, air comes in via the tank vent to displace the volume of fuel consumed. If the vent is clogged, it creates a vacuum in the tank and could cause it to collapse. You need to find out where the pressure is coming from. If the vent is working, you should get no vacuum or pressure.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I'm adding the diagrams from my 190DT, most Mercedes Diesel fuel systems are a variation on this theme.

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99.999% odds are the Fuel tank vent or tube is plugged.


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