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  #1  
Old 04-30-2019, 05:18 PM
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W123 Diesel is coming out of my gas tank

1981 240D, Diesel is spilling down the side of the car out of the tank (I know, it’s not a gas tank). I did the obvious and replaced the fuel cap, but that didn’t help. I’ve seen a number of W123’s on the road with the right rear quarter panel covered with diesel.

Any thoughts?

Thanks

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1981 240D Four on the floor, Orient Red over Parchment, bought with 154,000 but it's a daily driver and up to 180,000 miles, mostly original paint and all original interior.

Last edited by koooop; 04-30-2019 at 05:39 PM.
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  #2  
Old 04-30-2019, 06:08 PM
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You're filling it too full? Does it do it in summer and winter? there is a little drain inside the filler door that drains to the ground, via a rubber hose inside the trunk. Yours must be plugged.
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  #3  
Old 04-30-2019, 06:18 PM
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Quote:
Originally Posted by t walgamuth View Post
You're filling it too full? Does it do it in summer and winter? there is a little drain inside the filler door that drains to the ground, via a rubber hose inside the trunk. Yours must be plugged.
Not filling it anymore than we ever did.

It just started doing this at the last fill up, where we live in Southern California there is no big swing in temperature between winter and summer so it doesn’t really make a difference.

I will clear the line, but this is a lot of fuel coming out particularly if I take a hard left.
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1981 240D Four on the floor, Orient Red over Parchment, bought with 154,000 but it's a daily driver and up to 180,000 miles, mostly original paint and all original interior.
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Old 04-30-2019, 06:24 PM
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Is the vent line plugged? Normally that results in vacuum, not pressure and leaking.

Is the filler pipe rusted out?
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  #5  
Old 04-30-2019, 06:46 PM
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One pic is diesel from making a slow u turn to park in front of my house, the other is what was there the next morning. Diesel was all over the right rear fender.
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W123 Diesel is coming out of my gas tank-c55941b6-f341-43fc-89bb-58b9169bee2f.jpg   W123 Diesel is coming out of my gas tank-ca11863c-cb81-45b7-82a5-d96dbb71b327.jpg  
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1981 240D Four on the floor, Orient Red over Parchment, bought with 154,000 but it's a daily driver and up to 180,000 miles, mostly original paint and all original interior.
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  #6  
Old 04-30-2019, 07:27 PM
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It has to be coming from around the filler lid.
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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  #7  
Old 04-30-2019, 07:41 PM
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Quote:
Originally Posted by t walgamuth View Post
It has to be coming from around the filler lid.
That’s what it looks like, I even made sure to buy a factory fuel cap. that’s what it looks like, I even made sure to buy factory fuel cap.

I just wasn’t sure if there’s some sort of check valve in there or if there might be baffles that just went bad.

Since I’ve seen these with diesel all over that fender before, I thought maybe there was a common issue that was known on the forum.
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1981 240D Four on the floor, Orient Red over Parchment, bought with 154,000 but it's a daily driver and up to 180,000 miles, mostly original paint and all original interior.
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  #8  
Old 04-30-2019, 07:48 PM
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Are you sure that both lugs on the filler cap were engaged?

The one time that happened to me, it was because I failed to completely engage the cap after filling up.
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  #9  
Old 04-30-2019, 08:38 PM
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Quote:
Originally Posted by tangofox007 View Post
Are you sure that both lugs on the filler cap were engaged?

The one time that happened to me, it was because I failed to completely engage the cap after filling up.
Yes, they look to be seated correctly.

Maybe I got a bad replacement cap?
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1981 240D Four on the floor, Orient Red over Parchment, bought with 154,000 but it's a daily driver and up to 180,000 miles, mostly original paint and all original interior.
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  #10  
Old 04-30-2019, 10:25 PM
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could be.
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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  #11  
Old 04-30-2019, 10:44 PM
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Right now the car has less than a half tank of fuel, the fuel cap is dripping diesel when I remove it.
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  #12  
Old 04-30-2019, 11:56 PM
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Could your vent plug be clogged and the tank is getting smaller due to the tank being sucked in?
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  #13  
Old 05-01-2019, 09:39 AM
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Quote:
Originally Posted by okyoureabeast View Post
Could your vent plug be clogged and the tank is getting smaller due to the tank being sucked in?
It's tough to create a vacuum when you have a leak.
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  #14  
Old 05-01-2019, 11:42 AM
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Quote:
Originally Posted by tangofox007 View Post
It's tough to create a vacuum when you have a leak.
Vacuum preceded the leak?

Vacuum sucks the tank to a smaller size. Then the cap is installed incorrectly/damaged/gasket deteriorates and creates a leak.
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  #15  
Old 05-01-2019, 02:04 PM
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Quote:
Originally Posted by koooop View Post
Right now the car has less than a half tank of fuel, the fuel cap is dripping diesel when I remove it.
With that 1/2 of tank try driving with out the Fuel Fill Cap and see if Fuel still comes out. If that cures the issue it has to be the tank vent.

Remove the cover in the trunk that blocks the view of the fuel tank and see if your tank has collapsed. If you tank was collapsing that would put the squeeze on the fuel inside of the Tank and it has to come out some where.

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