How can you tell when the fuel tank is full?

[Hindsight]

I've read a number of comments about FFR tanks having to be filled slowly or the automatic fuel pump shutoff nozzle continuously clicks. This makes sense because there isn't a vent on top of the tank that is large enough to displace air at the same rate as fuel is being added by the pump. So if you have to fill it slowly, do you just have to listen for fuel coming up the filler neck to know it's full?

I've thought about adding a 1/2" or 3/4" vent line that goes from the top of the tank up to the filler neck about 2-3 down from the gas cap. OEM cars have a vent like this. It allows the displaced air to vent out of the filler neck during pumping. I believe this should allow the pump to pump the tank full and the auto shutoff to kick in at the right moment, so you know the tank is full. I would still also have a separate vent line going to charcoal canister.

Anyone see any issues with this or reasons why it wouldn't accomplish what is intended? Or is adding fuel the slow way not that big of a deal and not worth the added effort of adding the filler neck vent?

[Wayne Presley]

I do that on all my cars, Cobras included.

[flynntuna]

Wayne do you add a vent check valve to the fuel tank?

[Wayne Presley]

Wayne do you add a vent check valve to the fuel tank?


No check valve since the vent is only open when the cap is off
http://www.ffcars.com/forums/17-factory-five-roadsters/248421-tired-splash-back-when-filling.html

[K3LAG]

Wayne,

With the Boyd tank is there any reason one couldn't install one of these 41915 in the hole where the vent goes, then attach the vent that goes to the charcoal canister to the top connection and a fitting up to the filler to the other?

Larry

[Hindsight]

Thanks for the link to the specifics Wayne!

Is there any reason you put the tank vent hole at the same plane as the top of the fuel filler tube where it meets the tank, as opposed to on the very top of the tank?

[Wayne Presley]

You can do that Larry

[Wayne Presley]

Thanks for the link to the specifics Wayne!

Is there any reason you put the tank vent hole at the same plane as the top of the fuel filler tube where it meets the tank, as opposed to on the very top of the tank?

On the cobra I did it because that location allowed me to add the vent tube through the fill hole.

[07FIREBLADE]

What did you do for the 818 though, the same mod or slightly different.

[K3LAG]

You can do that Larry

Thanks Wayne. Now I just have to come up with an equally simple solution for the filler end.

Larry

[Hindsight]

Thanks Wayne!

I was going to use a bung at both ends (tank and filler) but bungs are really thick and the tank is very thin. Tough to weld those two together (at my skill level anyway). I like your fitting idea for the tank.

[Hindsight]

Wayne, you forgot to add 1/2" fuel hose and 2" OD aluminum tubing to your price quote :P I got the tubing from McMaster and the hose from summit. Hose was expensive, only because summit doesn't sell 1/2" fuel hose by the foot (or if they do, it's really expensive) so I had to get a 25' roll.

I get to test out my welding skills on that fuel cap extension now.

[Wayne Presley]

I had the 2" tube laying around form the IC installs so no I didn't forget to add them :cool:

[flynntuna]

So on the 818, and not having a welder avail, would it be safe to have the filler attached to a section of hose then a section of pipe with a 90 degree fitting to another section of hose to the fuel tank. With the vent hose going from the fitting in the pipe section near the filler to a bulk head fitting on the tank?

[Hindsight]

So you are saying you are going to Tee off of a pipe you are splicing in to the rubber filler neck? It would work but you'd need a T that has two 2" fittings and one ~1/2" fitting. That might be hard to find.

If I do a good job of welding my filler cap, I may offer to do it for other folks.

[Wayne Presley]

So you are saying you are going to Tee off of a pipe you are splicing in to the rubber filler neck? It would work but you'd need a T that has two 2" fittings and one ~1/2" fitting. That might be hard to find.

If I do a good job of welding my filler cap, I may offer to do it for other folks.


I have the 2" tubing, a TIG welder and a bead roller :cool: Right before you weld it (not a day ahead, an hour ahead or ten minutes ahead ), brush the aluminum with a clean SS wire brush for .75" on either side of the weld area, make sure your tungsten is clean ( the Radnor E3 stuff works well with just about any metal) and tack in in at least 3 places around the tube before welding the complete bead.

[flynntuna]

That's right, with out a welder that's the only way I could think of to "McGiver" it. :rolleyes:

[Hindsight]

Thanks for the tips Wayne! It sounds like you are well setup to offer this service for folks. I don't have a bead roller and although I'd love to add it to my arsenal, I don't think I can justify the expense as a hobby. I've been making beads the ghetto way with a pair of wire crimper/cutters (basically crimping a bead in). Looks ugly and I wouldn't sell it to anyone like that but it works and is hidden by hose anyway haha.

[Wayne Presley]

Easy as 1,2 3...

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/818-build%201/20150514_142131_zpsavxbbp1w.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/818-build%201/20150514_142131_zpsavxbbp1w.jpg.html)

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/818-build%201/20150514_142236_zpsertkv3lo.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/818-build%201/20150514_142236_zpsertkv3lo.jpg.html)

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/818-build%201/20150514_142249_zpsugyew1lo.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/818-build%201/20150514_142249_zpsugyew1lo.jpg.html)

[Hindsight]

Beautiful. Certainly beats my cheap method:
http://i.imgur.com/A8WSRzIh.jpg (http://imgur.com/A8WSRzI)

[Wayne Presley]

Beautiful. Certainly beats my cheap method:
http://i.imgur.com/A8WSRzIh.jpg (http://imgur.com/A8WSRzI)



You are sooooo right!!!!!!!!!:cool:

[Frank818]

It's too late for me to drill a hole in the FFR tank, so teeing off the vent like Larry mentioned is the only thing I can think of. But the hose size is pretty small, would it really work?
How big a hose size we need to fit the "filling vent"?

[Hindsight]

Why is it too late to drill a hole? Should be able to remove the pump, reach in with your hand and a small cup to catch the shavings. If you have a couple shavings in there, it shouldn't cause a problem though, since there is a pre-filter before the pump.

You are going to need at least 1/2" hose for the air to vent quickly enough in my opinion. I was going to use 3/4" hose but it's hard to find 3/4" fuel hose and when you do it's expensive.

[K3LAG]

The hole in the top of the tank as well as all three of the connections on the fitting I showed above are 1/2 NPT. I'll use a 1/2" NPT to 1/2" Barb fitting for a 1/2" hose. I would think a 1/2" hose would be plenty big enough. Wayne's post above shows that he uses 1/2"

Larry

[Frank818]

Good idea Hindsight! My tank is super hard to fit in place and a pain to remove as well, unless it leaks while I drive, I will never remove it again. But your idea is great, I'll do something like that. tnx :)

[Hindsight]

So I've hit a snag on this modification.

The new 818 tank from FFR has aluminum cockpit panels that only allow for about 2.5" or so of space above the tank. So the issue becomes: Where do you put the bulkead fitting for the large diameter vent? My preference is to do it on TOP of the tank for best venting but so long as it is up high on the side, it shouldn't matter. But then there's an issue with that as well: There are no openings on the left side of the tank to allow you to get in there with a hand or a wrench to hold the nut for the bulkhead fitting. All the tank openings are all the way on the right side of the tank. You could put the bulkhead fitting over near the fuel pump openings, but then you'd have to run the vent line horizontally all the way over to the left side and up. The line will sag and fuel will get trapped in the sag which you don't want.

The only solution I could come up with is to cut a hole in the left side of the tank, maybe on the bottom, then use it as an access hole while you install the bulkhead fitting, then weld the access hole closed and hope you don't have to remove the fitting any time soon (which you shouldn't). Not ideal but I don't see another option, does anyone else?

Last thought on this is that there is no rollover valve protection with the new tank. So I thought about using a rollover valve bulkhead fitting instead of a plain bulkhead fitting, but most of these have 1/4" or 5/16" barbs. Not big enough for the fill vent.

[Wayne Presley]

Just TIG a threaded bung on the top of the tank and be done with it.

[Hindsight]

That's a good idea. I thought about doing that but couldn't find a rollover valve with an NPT on one side and a 1/2" barb on the other. However, I think I'm over-complicating things and will just do as you suggest by using an NPT for a 1/2" vent (without a check valve) that will then have a 1/2" hose that connects to the top of the filler. Then I'll run 1/4" line off the existing fuel pump top plate, to an inline rollover valve, and then go up and back down as the main fuel tank vent.

[Mechie3]

Question on the venting:

Is it the back pressure created by the charcoal canister and associated tubing that prevents quick venting or is it the size of the vent itself limiting airflow? If it's the size of the vent, then T-ing off the top doesn't fix anything. If it's the charcoal canister restricting flow then adding a second T-d in line would help. Just trying to determine what route I want to take.

[Hindsight]

So there are two paths for air to escape as it is being displaced by fuel. The first is through the charcoal vent but think about the size of the vent hose and the restriction of the charcoal canister and then think about how quickly a gas pump is pushing liquid into the tank. So obviously that isn't going to be big enough.

The next path is for air to escape back out the filler tube. It's large diameter so it can certainly support the flow rate, however, bends in the pipe can cause fuel to pool (even if for just a second at a time) and prevent air from escaping, and also the placement of the filler pipe on the tank is BELOW the top of the tank which creates an air lock inside the tank giving the air no place to go. If the filler connected to the very top of the tank, it wouldn't be as much of an issue, though again, bends in the filler pipe could cause a lock... have you ever filled oil or coolant with a funnel and when you poured fast enough and had the funnel tight against what you inserted it to, the fluid blocked the air from escaping and caused a mini explosion of oil/coolant into your face? I have :( Same thing.

So what you need to do is add a place for the air to escape from the top of the tank, and it should be large diameter. It only needs to be there during fill, so should be sealed under all other conditions. So you route a hose from a new fitting on top of the tank to very close to the gas-cap end of the filler neck. The placement of the hose connection on the filler neck should be ABOVE the fuel nozzle when it's already inserted. The vapor will escape from around the fuel nozzle and out into the air or get sucked up by the fuel nozzle vapor recovery system.

I have pics of what I did in my build thread. Basically just welded an NPT bung to the top of my tank right above where the fuel filler pipe connects, then screwed an NPT 90 degree elbow barb fitting to it, then welded an aluminum bung to the filler housing, added another elbow to that and connected them with 3/4" (or 1/2" I forget) fuel hose.

http://thefactoryfiveforum.com/showthread.php?15217-Hindsight-s-build-thread&p=199081&viewfull=1#post199081
http://thefactoryfiveforum.com/showthread.php?15217-Hindsight-s-build-thread&p=202740&viewfull=1#post202740
http://thefactoryfiveforum.com/showthread.php?15217-Hindsight-s-build-thread&p=202864&viewfull=1#post202864

[Mechie3]

Some people talked about Teeing into the existing rollover vent/valve. It's certainly easier. I was wondering if that was enough, or if it's necessary to drill. Asking because I don't want to drill. Lol.

I was actually reading through your thread right now.

[Hindsight]

You could T into that vent but the metal barb that is part of the tank top for the vent is not going to be big enough. It's maybe 1/4" at the most and I think maybe even more like 3/16".

Tell you what, I'll do your tank if you'll do my stupid 6-point harness anchors lol. I swear, TIG welding on my back underneath the car has been my least favorite activity.

[Mechie3]

I just drilled right through the X bar.

[Hindsight]

That's what I broke down and did last night. Not happy with it since that doesn't provide a ton of strength but the two anti-sub anchors will see the lightest loading of all six points.

[Mechie3]

Yep. Later on I'd like to go back and weld some shoulder flanged spacers in there.

[Frank818]

Sounds like another 0DB CNC part coming up. :)

[farawayjeff]

If welding a bung at the filler end is simply not an option, you can use a no weld oxygen sensor bung. Just remember that the barb fitting you get for it needs to be M18 1.5 at the threaded end.
61564

[Frank818]

What does that bung do? You fill up fuel until it pours out from the bung? And where does it go?
I have done such a hole and connected a 3/4" hose to the top of the tank, for air pressure circulation, but I don't see how that will tell me the tank is full.

Also did you modify your filler neck pipe? Or it came with that 2" rubber hose in the middle?

[RM1SepEx]

The bung allows air in Frank, the pump pops off due to pressure build up, it thinks it's full. I don't have one, pump at 1/2 speed it's fine. You don't save time filling faster, it always takes longer to tell people what it is and let them take photos than it does to fill up!

[Frank818]

Does the bung need to be at atmosphere like that or connected to the top of the tank? I believe the second. In which case I should be fine with my setup.
I didn't know it was pressure making the pump turn off.

[phil1734]

The pressure builds up in the filler neck early because there is air trapped at the top of the tank. Fix that and you fix both issues. Some simply vent to atmosphere, others a charcoal can, others run it to the top of the filler neck.

With the new tank design there is provisions for a vent. The old tank does not have it. I'm not sure how the Boyd tank is set-up.

[Frank818]

Cool! I didn't know the vent would fix both. Learned something new again today.

I think the Boyd has a vent for that if I recall seeing the pictures.

[AZPete]

You don't save time filling faster, it always takes longer to tell people what it is and let them take photos than it does to fill up!

Thanks, Dan, for reminding me I don't need this vent. You've got more miles and fill-ups than me but I've found it takes at least 15 minutes to answer questions at gas stations. I'll even admit to gas stops at a crowded station when the tank is half full just because it's fun.

[farawayjeff]

Frank, the no weld bung holds a fitting that connects to a 1/2 vent pipe running from the top of the tank. Should vent the same as yours.

I have the Boyd tank so the ffr provided filler pipe does not fit. To make it work I cut the center section out. I kept the 45 at the top and the 90 at the bottom. Those pieces plus the rubber connecting hose in the center make a nice fitting unit from filler cap to Boyd tank.