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  #1  
Old February 18th, 2012, 12:13 PM
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fuel system venting

I have a question about my fuel system. Truck is a ROW 110 with a 300 Tdi. My tank though, is from a RRC. Oftentimes after I fill up and start driving, fuel leaks out of the filler neck onto the side of the tub and also from other fittings. Seems to happen more often when it’s hot outside, so I guess a vacuum is being created?

I don’t have a vented fuel cap; will that solve the issue? What else should I check out in the fuel system?

I found this post on ECR’s facebook page about another truck and it sounds like I have a similar problem:

“They combined the 2004 300 Tdi fuel system with the tank from a 1980s 2.5 petrol and you can't do that. It leaves no venting for the tank (as the older tanks relied on a vented fuel cap). So every time you ran the truck it started sucking the tank in. Then when it sat in the sun it started pushing diesel out all the fittings due to the pressure.”

Any advice is much appreciated. Thanks.
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Old February 18th, 2012, 01:15 PM
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Not sure I have the charcoal canister; where should it be? Sorry, new at this..

Thanks Jeff.
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Old February 18th, 2012, 01:33 PM
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When I converted a '97 D90 to a tdi, besides having to gut the submerged fuel pump, I took out the little spring loaded vent valves in the vent line on top of the tank. This vent line goes all the way into the engine compartment. Since it should draw in air, as fuel is removed from the tank, I put a small in-line fuel filter on it the keep dust from being sucked into the vent line and eventually, the tank.

The tank needs a vent in the top of it, otherwise when the fuel gets hot, when the tank is full, it'll push fuel out the filler neck.
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Old February 18th, 2012, 01:47 PM
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I would run a vented fuel cap and plug everything else to keep it simple. I can imagine the early caps could hold any vacuum.
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Old February 18th, 2012, 02:04 PM
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Quote:
Originally Posted by evilfij View Post
I would run a vented fuel cap and plug everything else to keep it simple. I can imagine the early caps could hold any vacuum.
I'd say what is most likely happening is fuel is being forced up the filler neck not because of vacuum but fuel & air expansion in the tank, thus forcing the fuel to escape out the fuel cap.

------ Follow up post added February 18th, 2012 11:09 AM ------

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Originally Posted by tommyd View Post
Seems to happen more often when it’s hot outside, so I guess a vacuum is being created?

Any advice is much appreciated. Thanks.
If vacuum was being created, the engine would die (fuel starvation) OR the tank would collapse, if the vacuum were severe enough.

The problem is excess pressure in the fuel system, not vacuum.
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Old February 18th, 2012, 03:38 PM
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Quote:
Originally Posted by JSBriggs View Post
The RRC tank has a vent the normally would go to the charcoal canister. Did you cap it?

-Jeff
I see a line coming out of the top of the tank; is this the one you mean?
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Old February 18th, 2012, 03:43 PM
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Thanks Ron and Dennis.

So will a vented fuel cap resolve this? Or do I still need to do something with the vent on top of the tank?
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Old February 18th, 2012, 03:50 PM
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Originally Posted by tommyd View Post
Thanks Ron and Dennis.

So will a vented fuel cap resolve this? Or do I still need to do something with the vent on top of the tank?

That vent line needs to run to a higher elevation to allow air into the tank. The end of the vent hose should be at least a foot higher than the top of the fuel fill Point (gas cap). Mine runs up to the engine compartment and is at the elevation equal to the top of my radiator. If you run a short hose, fuel sloshing in the take while off road can make it squirt out of the end of the hose.

If you need to buy some vent line you probably use some of the drip line semi-rigid tubing used in irrigation. I't some-what rigid, but flexible enough to deal with. Zip tie it to the fuel line that goes to your fuel filter up in the engine compartment. You'll need some small pieces of rubber fuel line to joint it to the ends and remember to put on a small fuel in-line filter to keep dust out of the vent line
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Old February 19th, 2012, 12:17 PM
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Quote:
Originally Posted by Dennis View Post
That vent line needs to run to a higher elevation to allow air into the tank. The end of the vent hose should be at least a foot higher than the top of the fuel fill Point (gas cap). Mine runs up to the engine compartment and is at the elevation equal to the top of my radiator. If you run a short hose, fuel sloshing in the take while off road can make it squirt out of the end of the hose.

If you need to buy some vent line you probably use some of the drip line semi-rigid tubing used in irrigation. I't some-what rigid, but flexible enough to deal with. Zip tie it to the fuel line that goes to your fuel filter up in the engine compartment. You'll need some small pieces of rubber fuel line to joint it to the ends and remember to put on a small fuel in-line filter to keep dust out of the vent line
Dennis,

Do you get any raw diesel smell, or does the filter take care of that?
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Old February 19th, 2012, 07:35 PM
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Originally Posted by michael67 View Post
Dennis,

Do you get any raw diesel smell, or does the filter take care of that?

No, I don't have any diesel smell in the engine compartment. If you having smell issues, I'd 1st suspect a leak at the rubber hoses that run injector to injector. The I'd check all hose ends and clamps that carry diesel, also the fuel filter seal and the drain on the bottom of it. I got the filter idea from my '85 BMW 524td, it has a filter on the fuel tank vent line in the engine compartment.
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