Fuel Tank Venting

On my box truck, I am using an aluminum fuel cell designed for a race car. It has 3 ports (vent, return, out) and I have only been using the out port plumbed to my TNT. A kohler engine doesn't use a loop system so there is no return line so the port is capped off. I have also capped the vent for now and would crack the fuel fill cap instead to provide the vent.

Needless to say, venting by the fuel cap is not the safest of plans, but if I don't, I get fuel vapors being forced out of the sending unit seal.....also not a good thing.

What I am looking to do is the following:

First, I need to attach a hose barb fitting to the tank's vent port. This comes with a twist as they are 8 AN fittings, but I actually want a 5/8 inch hose barb....which doesn't seem to exist. I can get a 3/8 or 5/16 only for that size of fitting. This is important for the next step.

Second, I want to run a fuel hose from that vent barb up a couple of feet to a marine-style fuel vent. You know what these are Mo, as it is on your boat as well. They are almost like a dryer vent in that they have a little dust shield and check valve at the end. Anyway, I want to run that up high and then either mount it outside permanently or else be able to hang it outside when in operation. These vents only come with 5/8 inch barbs....hence my problem. I really don't want o use brass reducers in the hoses as I don't want to risk vapor escape at all.

I ordered the tank fitting and the marine vent, but they will not be here until this weekend. In the meantime, anyone have a better idea? I am open to suggestions. I do keep all the doors rolled up when running the TNT, but since the LG heater is just a few feet away behind the partition, I don't want to risk vapors drifting inside the box.

For those that prefer visuals:

This is the fuel cell.

This is the Marine Fuel Vent
his is the Marine Fuel Vent

You can use black pipe reducer, then use a propane line from lowes I think it's 1/2 in then fit it to the tank. No barbs, besides a standard hose will hold 60 to 100 psi with barbs you will not have anywhere near that much psi.

Good call on the pipe....didn't think about that at all.

Does the venting plan make sense to you?

Im having trouble with my #4 Little giant regulator.

its leaking out of the vent and its the second one I have bought in less than a year. Cant figure out why they are going out.

this one is only 8 months old

Where are you getting your tank filled. I just replaced one that was less than a few weeks old. He had it refilled and they used a line with to much pressure and it ruptured the diaphragm in the regulator. Something to think about.

The vent is ok but it should work both ways in and out. In so you can get fuel to the unit. out to relieve tank pressure when not in use.

Yeah I have that vent on my portable tanks. You vent it by turning the nut on the fitting. Some guys forget to vent their tank and get stuck out on the lake cuz they forget to vent the tank.

Having the LG and fuel cell in truck would just make me nervous. I would have just fuel tapped it. Less weight and more space in the van

ACE Services wrote:Where are you getting your tank filled. I just replaced one that was less than a few weeks old. He had it refilled and they used a line with to much pressure and it ruptured the diaphragm in the regulator. Something to think about.

hmm, good point its at a gas station right by my house. I always have them purge the tank which they didnt know how to do which I thought was weird, had to show them.

Ill have to look into how much pressure they are using, maybe they can dial it back a bit?

ACE Services wrote:The vent is ok but it should work both ways in and out. In so you can get fuel to the unit. out to relieve tank pressure when not in use.

its leaking out of the small vent on regulator as soon as tank is open. Last summer it happened and I called up little giant, they said reg was toast so I had to order another... its was 175.00 plus shipping.

I tried to find the model online its a Rego brand 450L, looked like there was one on ebay for around $50 but couldnt tell if that is used

Mo wrote:Yeah I have that vent on my portable tanks. You vent it by turning the nut on the fitting. Some guys forget to vent their tank and get stuck out on the lake cuz they forget to vent the tank.

Having the LG and fuel cell in truck would just make me nervous. I would have just fuel tapped it. Less weight and more space in the van

I didn't have choice....truck is a diesel.

Looking back, I wish I would have put the LG on the other side and moved the hose reel down a compartment. Then again, the propane tank was supposed to be beneath the LG on the driver's side, so it made sense at the time.

My van is smaller but I have my propane underneath right behind the driver side and the LG is on the side door passenger side. The hose is probably 6 feet long

Six feet isn't bad, but I would have to cross over the truck's exhaust and that didn't feel like a good idea at the time.

Once the vapor is properly vented outside, I don't see any problems. The propane bottles sit outside the truck on the ground when in operation and the LG is protected from the wind so the staging might be okay.

I guess I could change it around this winter based on how it works out.

I thought I should close out this thread with the results.

I installed the marine vent in the following way:

1.  Mounted the vent to the outside on the front of the truck box near the top.  The only reason for that location is that the box is all double walled except up by the marker lights, so it was just easier.



2.  Then I ran the fuel hose from the vent down along the stainless shelf and anchored it there with cable ties.



3.  It then runs to the tank at about a 15-20 degree angle before attaching to the 8 AN fitting on the tank.



It would have been cleaner just running it out the box below the shelf, but I really didn't want to mess with double walls.  This is over-kill for a vent, no way in hell could fuel get sucked up that far, but it was just easier to mount the vent in that location.

At least the problem is solved for now.

Looks goodto me.

Thanks ACE, I do feel better about it now.

looks nice Rob. I got my regulator venting problem figured out. Took a while surprisingly to get little giant on the phone but when I did the tech support guy told me they have switched to a new regulator because they were having issues with the Rego brand.

new one is in the mail free of charge, should have it by late next week.

What brand / model is the replacement?

cant remember ill let you know as soon as it comes