Fuel Tank Breather Modification

[6 Nebraska IDIs]

I'm going to do a write up on this because I've searched and found absolutely no detailed instructions how to do it, and to be honest with a little guidance it would be an easy project for anyone.

Heres a little outline on what I did, I'm going to post up more pics and step to step details but here's the basic outline.

I started by finding the fuel tank rollover valve, since I had no idea where it was at. It is a little white plastic pod on the top of the fuel tank with a 1/8" hose coming out of it. This valve needs to be removed entirely if you wish to truly make a free flowing tank filler neck.
I took the valve out as well as the grommet that seals it into the tank and used it to come up with a few ideas for routing the new breather hose.
Here's all the parts I used to create the recirculating breather.

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There's one thing I decided to change, I bought both a 90* 3/4"-1/2" pex fitting as well as the straight one shown. The 90* one makes the install much more adaptable so I used that one in my current setup thats in my truck.

The hose is 3/4" diameter, plenty big. The copper fitting and reducer need sweated together, but that piece fits perfectly into the tank rollover valve grommet.

I put a flat spot on and drilled a 1/2" hole into the frame side of the upper portion of the tank filler neck, installed the small grommet into the hole and popped the pex elbow into the grommet. I then put the hose onto each end of the fittings and clamped them down. I haven't tested it yet, I didn't feel like driving into town just to try it, but I'm sure it'll work great!

All total, for the parts for both tanks I spent $33 at the hardware store.

 

[Wanderin]

I put a flat spot on and drilled a 1/2" hole into the frame side of the upper portion of the tank filler neck, installed the small grommet into the hole and popped the pex elbow into the grommet. I then put the hose onto each end of the fittings and clamped them down.

If you dont have some way for the tank to draw air you will create a vacuum and start having fuel issues. The rollover valve allowed air in/out and a small ball would plug the hole if you rolled over. Diesel does not evaporate like gas so its ok to vent the tank over one of the rear wheel wells and works fine. Hope this helps .

 

[6 Nebraska IDIs]

What I could find on here about it were guys talking about doing what I understood to be similar to what I did but none of them really said enough about it to make it clear. I talked to 3 other guys from the forum over the phone about what the modification intailed and they all said the way I was doing it was exactly how they had done it, they just hadn't found a way to use readily available parts to do it.

Anyway, you absolutely cannot vent this modification to the atmosphere or you WILL empty your fuel tanks into the earth in the event of a roll over. I'm sure this is why other guys have used the same concept for their breather modification. You do pose a good question, but my tanks already would go into vacuum when I ran them, actually I think all my trucks do. I guess we will see if this causes any problems.

 

[Wanderin]

Read last paragraph HERE...i know 'most' people here dont have plastic tanks, but if you create a vacuum in your tank you are making your pump work harder/wear out sooner.

 

[6 Nebraska IDIs]

Thanks for the link. I've got a few extra PCV valves sitting around, I wonder if those will work well enough for a vacuum relief check valve.

 

[1994Diesel]

Thanks Sean! This doesnt look like a costly mod at all and could cure my "shutting off every two seconds" pumping problem when trying to fill up my truck.

 

[franklin2]

I am not sure about this, but if our trucks use the same fuel cap as the gasser trucks, those caps will let in air, but not let fumes out. So if we do have the same caps as the gassers, you should be ok in the vacuum department.

 

[typ4]

Never had a problem with mine in 5 years, the caps let in enough air,and let out pressure, Gas caps do not.

Good Idea on the pex elbow, easy fix for next time.

 

[jwalterus]

a rubber-flap-style plumbing check valve would do the same as the rollover valve did

I've gotten them down to 3/4" for sump-pump installations on a garden hose

 

[6 Nebraska IDIs]

Ok Update on how well this works. I've yet to see any vacuum issues with the tank, but I'll wait and see. I do have the old twist lock metal gas caps on this truck, its the way it came from the factory.

Anyway, I was able to fill the tank the mod was completed on full blast with the regular diesel pump, I went to a station that has been well known to use gas pumps to pump diesel (this causes the fuel to foam more) so basically you are pumping foam and not fuel. Most stations around here use this trick to con you into thinking you're pumping more measured fuel into your tank where in fact its just foam.
Anyway I went there knowing it was like this simply because I wanted to see what the worst of the worst possible pumping situations would be like.
It foamed allot into the neck but instead of backing all the way up and poofing out of the fill neck like it used to the foam would kind of roll and circulate down into the tank. I want to say I was not able to stick the nozzle into the neck like you should be able to though and get it to keep pumping. If I did that it would shut off, but I think this was because of the simple fact I was pumping pure foam so I'm hoping an actual diesel pump that pumps like normal would be able to set all the way down in the neck and keep pumping.
Overall I'm very happy with this mod. I've been used to holding the nozzle up in the neck for some time so I don't mind it. The mod accomplished what it was supposed to, allow for faster fueling times.

 

[idiabuse]

I sure hope a filter makes it onto the end of the vent tube. Keeps sediment from getting into the fuel tank, dont take long either...


Javier

 

[6 Nebraska IDIs]

The point of this was to not go about it the way any joe blow idiot does it, like the guy who previously modified this fuel tank in my truck, and vents it to the atmosphere. There are 2 reasons you do not do that, 1 is as you stated, sediment can get sucked into the tank if its vented to open atmosphere. The 2nd and most important of all is that in the event of a rollover the fuel tanks will simply empty into the earth, so DO NOT half ass this mod and vent it to the atmosphere! IIRC its a $10,000 fine per gallon of fuel that leaks into the earth, so your pocket book is going to hurt even more in the event you roll over and it dumps all your fuel out. I want to make it clear again, BE SURE to install the vent hose into the filler neck, DO NOT VENT IT TO THE ATMOSPHERE.
No filter is needed on this because it recirculates the fuel tank vent into the filler neck. The reason I posted this is because there arent any really good writeups on it and everyone I've read about in the past has tried soldering or brazing the fitting into the filler neck. If you tried that you'd understand how big of a PITA it is to get that filler neck to stick to something. So thats why I used the grommet and the pex fitting because it simply pops into the grommet after you've flattened your spot on the filler neck and drilled your hole. Its a very simple installation, simple enough people shouldn't have any excuse to half ass it.

 

[BlindAmbition]

I followed the idea from the beginning of this thread for my fuel filler neck. Ut took me a couple of reads for it to make sense, adding pictures in case it helps someone else. I may have drilled into the wrong side, will see how it works out when installed.

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[riphip]

Google 'Harpooning the tanks'
Been done for years. Did mine back 15+ years ago. Fill your tanks quick with no spewing. Rip out the fill baffle.

 

[franklin2]

Just make sure you are able to stick the fuel station nozzle past the air return fitting you install. That makes sure the air coming out during filling is out of the path of the fuel flow from the nozzle.