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  #1  
Old 12-04-2016, 05:15 PM
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1995 E300 pressure in fuel tank

My 1995 E300 has started building air pressure in the fuel tank whenever the engine is running. The engine has stalled a few times on me when I stop at a stop sign. I opened the fuel cap on the tank a bust of air rushed out.I have since been driving the car with the fuel cap not screwed down tight and the stalling problem has stopped.
What would cause this pressure to build in the tank?

Thanks for your help.

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  #2  
Old 12-04-2016, 06:50 PM
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Probably a plugged tank vent valve or plugged tank vent line.

See post # 13 on this thread.
http://www.peachparts.com/shopforum/diesel-discussion/212289-fuel-tank-vent.html
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  #3  
Old 12-05-2016, 11:53 AM
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1995 E300 pressure in fuel tank

More likely a vacuum situation, rather than pressure, caused by the blocked tank vent line or valve mentioned by alex300SD. As the fuel is withdrawn from the tank, a partial vacuum is created since the venting system cannot equalize the tank to outside atmosphere, making the pumps work harder and eventually stalling the car. You've bypassed the clogged venting system by leaving the fuel cap open.

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Tom
'95 E300D
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  #4  
Old 12-05-2016, 03:11 PM
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Quote:
Originally Posted by Old Barn Guy View Post
More likely a vacuum situation, rather than pressure, caused by the blocked tank vent line or valve mentioned by alex300SD. As the fuel is withdrawn from the tank, a partial vacuum is created since the venting system cannot equalize the tank to outside atmosphere, making the pumps work harder and eventually stalling the car. You've bypassed the clogged venting system by leaving the fuel cap open.

Regards,
Tom
'95 E300D
It's a pressure situation for sure. If I fill the tank drive for a few miles and open the fuel cap I get a diesel fuel bath!
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  #5  
Old 12-05-2016, 03:48 PM
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it's your lift pump pulling a vacuum through the fuel line O-rings. you likely have a clogged pre-filter. it's sucking air in past the O rings and it ends up trapped in the fuel system.
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  #6  
Old 12-06-2016, 09:30 PM
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Suggest replacing the lift pump.

Rgds,
Chris W.
ex 95 E300D, 467K
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Old 12-06-2016, 09:39 PM
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Quote:
Originally Posted by Chris W. View Post
Suggest replacing the lift pump.

Rgds,
Chris W.
ex 95 E300D, 467K
What is a "lift pump" and where is it located?
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  #8  
Old 12-06-2016, 10:39 PM
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Does this have a pressure re-circulation pump for the gas tank like the 95 C280 ? Driver side inner fender toward the headlamp. Cylindrical pump that exhibits "heart-beat" vibration when grabbed.
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  #9  
Old 12-07-2016, 02:46 AM
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Quote:
Originally Posted by packerfan View Post
What is a "lift pump" and where is it located?
The lift pump is the mechanical fuel pump on the side on the injection pump.
Possible but unlikely that the crush washers on the lift pump are leaking.

The pre-filter can be clogged or its o-ring way have deteriorated.
The o-rings on the fuel lines can fail to seal as they deteriorate over time.
Fuel may not leak out , but air can leak in if they are dried out from age and engine temperature.
Perhaps just replacing the o-rings and/or the pre-filter with its o-ring is what is needed?
The car is 21 years old, when were they last replaced?
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  #10  
Old 12-07-2016, 11:50 AM
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I have the same issue. Pressure release when taking the cap off an empty tank (doesn't always happen). While I agree with the vent being blocked (caked with dirt), I'm interested to see about the lift pump pulling in air.

I'm up for a secondary filter change and I'm seeing some slight weeping at the center bolt. I'll pull the primary as well and see if I have any issues to note.
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  #11  
Old 12-07-2016, 12:23 PM
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Check the tank strainer for gunk, many look like this including mine.


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