The fact that the vent inlet is that far below the top of the tank, and the implications of that, is obvious now that you say it, but I didn’t even think about it before I installed mine a couple weeks ago. How are you modifying it?
Community
Buy / Sell
Bronco Tech
Fuel Tank Access Plate
3 Arm Wiper Setup
Fix Motor Mount
Roll Cage Braces
Throttle Body 65mm
Wheel Alignment
Heat Riser Replacement
Vent Window Repair
Center Console Mount
Straighten Bumper
Ford 6R80 6 spd
More Tech...
3 Arm Wiper Setup
Fix Motor Mount
Roll Cage Braces
Throttle Body 65mm
Wheel Alignment
Heat Riser Replacement
Vent Window Repair
Center Console Mount
Straighten Bumper
Ford 6R80 6 spd
More Tech...
-
Welcome to ClassicBroncos! - You are currently viewing the forums as a GUEST. To take advantage of all the site features, please take a moment to register. It's fast, simple and absolutely free. So please join our community today!If you have problems registering or can't log into your account, please contact Admin.
Gas Tank vent
- Thread starter snipes243
- Start date
The fact that the vent inlet is that far below the top of the tank, and the implications of that, is obvious now that you say it, but I didn’t even think about it before I installed mine a couple weeks ago. How are you modifying it?
- Joined
- Oct 8, 2019
- Messages
- 587
The valve I posted has a float in it to keep fuel out of the tube. I guess if it works, the cap becomes the overflow.
I don’t know if it’s all going to fit or work yet.
Sent from my iPhone using Tapatalk
Then it's not a vent anymore. And there are plenty of victims on this forum that installed a rollover vent valve without success. They are not designed to be submerged.
The problem with the cap is that if it is "Pressure-Vacuum" cap, then it won't vent.
If its "vented, anti-surge" then it will only allow air into the tank, but won't resolve pressure.
If you drill a hole in the cap, then the cap makes a great vented cap. But if you ever lay your Bronco on it's side, you are gong to dump 23 gallons of "hi-test" in the middle of the trail.
Paul @DirtDonk has dealt with this plenty.
@neilvonarb , I just add a Rollover vent valve mounted to the top of the fill neck. That giant 5/8 diameter vent hose at the very top of the tank is very effective as a vent. I can send some pics tomorrow after I install mine.
- Joined
- Oct 8, 2009
- Messages
- 1,559
You mentioned replacing rubber fuel lines. Just to double check, where did those come from? Are they designed to handle fuel? If not, I wonder if they could be the cause of the black residue.
You might also try bypassing the charcoal canister temporarily. Maybe run a temp vent hose to a high location, loop it back down into a can on the ground while it's parked. Use a tee open to the atmosphere at the top of the loop to break the siphon if the fuel starts down the the other side of the loop. Probably with a little stand pipe on the open side of the tee. The catch can would show how much fuel is being forced out. Having the charcoal can out of the system would help sort out if the black residue is coming from the charcoal. But that might take awhile if charcoal is already in the fuel.
All of that is for temporary testing, trying to hunt down an elusive problem, not a permanent fix. And will likely leave you with a fuel smell in the air.
I do a lot of plumbing on home remodels. We're into double checking territory here, so please ignore me if you've already got this stuff sorted out. Remember the old saying "water seeks its own level". That applies to any liquid. If you fill your tank so high that it fills the filler neck, it also fills anything lower than the height of the fuel in the neck. Including the charcoal canister if its below the neck. Unless the rollover valve completey blocks it. Its why they recommend to never fill the neck.
Occasionally in a house I install a filter or aerator that contains charcoal. Those always have to be flushed thru thoroughly to get past the gray/black water that comes out at first. With an automotive charcoal cannister, I wonder, since the fuel doesn't flow thru it in one direction, but instead would fill it, then return back the way it came, would it ever completely flush that residue out?
You might also try bypassing the charcoal canister temporarily. Maybe run a temp vent hose to a high location, loop it back down into a can on the ground while it's parked. Use a tee open to the atmosphere at the top of the loop to break the siphon if the fuel starts down the the other side of the loop. Probably with a little stand pipe on the open side of the tee. The catch can would show how much fuel is being forced out. Having the charcoal can out of the system would help sort out if the black residue is coming from the charcoal. But that might take awhile if charcoal is already in the fuel.
All of that is for temporary testing, trying to hunt down an elusive problem, not a permanent fix. And will likely leave you with a fuel smell in the air.
I do a lot of plumbing on home remodels. We're into double checking territory here, so please ignore me if you've already got this stuff sorted out. Remember the old saying "water seeks its own level". That applies to any liquid. If you fill your tank so high that it fills the filler neck, it also fills anything lower than the height of the fuel in the neck. Including the charcoal canister if its below the neck. Unless the rollover valve completey blocks it. Its why they recommend to never fill the neck.
Occasionally in a house I install a filter or aerator that contains charcoal. Those always have to be flushed thru thoroughly to get past the gray/black water that comes out at first. With an automotive charcoal cannister, I wonder, since the fuel doesn't flow thru it in one direction, but instead would fill it, then return back the way it came, would it ever completely flush that residue out?
Here's a pic... The best thing that ever happened to that submerged vent port is a pipe plug.
Attachments
So it vents to itself? What kind of gas cap will you use?
No, that vent port attaches to a roll-over vent valve mounted high in the rear quarter.
I use a pressure-vacuum cap. I wanted to be able to lean the Bronco over on the trail without fuel spilling out.
JKH67302
Full Member
- Joined
- Apr 25, 2009
- Messages
- 189
I had the same issues with my M1A1 and it eventually flooded a charcoal canister. The vent is too low as jamesroney mentions. I copied his idea (thanks jamesroney!), I used a weldable barb from jegs and placed the port on top of the fuel neck (high as i could get it and still service the hose). I then ran my vent line from there too my stock style (delorean) 76-77 roll over valve, and then on to the evap canister. I use the later style fuel cap as well. Problem solved and no issues on trails either.
Sent from my SM-G975U using Tapatalk
Sent from my SM-G975U using Tapatalk
Where did you mount the roll over valve? Mine is same type (DeLorean) as yours. I just mounted mine and am second guessing the location…
- Joined
- Oct 8, 2019
- Messages
- 587
I ended up putting one of these in mine. Not quite as good as moving it higher but it will keep fuel out of the line and vent fine unless the tank is completely full.
https://www.summitracing.com/parts/tnk-vv
Sent from my iPhone using Tapatalk
https://www.summitracing.com/parts/tnk-vv
Sent from my iPhone using Tapatalk
Bringing this tread back to life. I too have the M1A1 tank, and I plugged the vent on the tank. Now I'm trying to figure out my game plan for tank venting.
Why can't the filler vent be routed to the evap canister on my 73 Bronco? My thought was to cap the metal tube on the filler tube. Then I would connect the filler tube vent connection
coming from the tank as the connection to the evap system. I'd put in a similar check valve in the line to prevent gas passing that valve.
Why can't the filler vent be routed to the evap canister on my 73 Bronco? My thought was to cap the metal tube on the filler tube. Then I would connect the filler tube vent connection
coming from the tank as the connection to the evap system. I'd put in a similar check valve in the line to prevent gas passing that valve.
DeezNCSU
Full Member
- Joined
- Mar 12, 2014
- Messages
- 249
Reviving this again as I think I'm having the same problem and I want to make sure I'm handling it properly. I have a '68 with stock tank, filler neck, blueprint 302 with carb. I've had two instances where I've gotten gas on the way home, haven't intentionally overfilled it, meaning when the pump clicks off I stop filling then when I get home and park it and it sits for a few days, I get an intense gas smell and find that gas has started leaking from the cap. I think I have the correct venting gas cap.
Outside of filling it less than I am, is there anything else I should be doing or checking?
Outside of filling it less than I am, is there anything else I should be doing or checking?
- Joined
- Nov 3, 2003
- Messages
- 51,622
Back in the day, it seemed like most Broncos had a smeared of faded paint below each filler cap where Gas would leak out regularly and mess up the paint.
That was SOP back then. Until 70 or 71 when the venting came in into play. Which also meant less capacity.
Do you know how much gas you put in when the tank is empty? Are you running a single tank or duals?
That was SOP back then. Until 70 or 71 when the venting came in into play. Which also meant less capacity.
Do you know how much gas you put in when the tank is empty? Are you running a single tank or duals?
DeezNCSU
Full Member
- Joined
- Mar 12, 2014
- Messages
- 249
Unfortunately, this did cause a paint blemish which sucks! It's a single tank.
I'm not sure, I didn't look at how much I added, I just stopped once the pump clicked off.
I used to have that problem with a non bronco if I filled up in the summer, being careful to not over fill but would have gas leaking out of the cap due to the gas warming and expanding. On that vehicle I added liquid/vapor separator to capture and return to the tank the expanding fuel. Has worked well, later broncos had a similar device.
DeezNCSU
Full Member
- Joined
- Mar 12, 2014
- Messages
- 249
Do you mind sharing an example of what you installed? I'll probably do the same so I don't keep having this issue.
- Joined
- Nov 3, 2003
- Messages
- 51,622
Unfortunately, having a single tank doesn’t let you do what those of us with dual tanks can do. Literally run one bone dry, then while still driving, switch to the full tank.
That way you can fill from empty and see what it holds. See how far you go.
Sounds like you have the opposite problem, from what many other people have. Where you can fill until it shuts off, which is apparently too much in your case. While others can’t stop the stupid things from shutting off!
You go about a quarter of a gallon at a time and it shuts off. So it’s pull click, pull click click, pull click, for about 20 minutes.
Where normal cars take five or less.
And yes, I’d like to see what Yeller did as well.
You could probably even take an old cast off recovery tank from a 70 and later Bronco, and mounted it underneath the rear fender up high.
You don’t really want it in the cab like FORD did it until 76 though.
A lot of us change the old 70 through 75 style to the 76/77 style. Maybe that’s easy to do here too, as long as you can put a vapor catch fitting somewhere on the tank or filler neck.
That way you can fill from empty and see what it holds. See how far you go.
Sounds like you have the opposite problem, from what many other people have. Where you can fill until it shuts off, which is apparently too much in your case. While others can’t stop the stupid things from shutting off!
You go about a quarter of a gallon at a time and it shuts off. So it’s pull click, pull click click, pull click, for about 20 minutes.
Where normal cars take five or less.
And yes, I’d like to see what Yeller did as well.
You could probably even take an old cast off recovery tank from a 70 and later Bronco, and mounted it underneath the rear fender up high.
You don’t really want it in the cab like FORD did it until 76 though.
A lot of us change the old 70 through 75 style to the 76/77 style. Maybe that’s easy to do here too, as long as you can put a vapor catch fitting somewhere on the tank or filler neck.
ntsqd
heratic car camper
IF (big word) I'm understanding your idea correctly you won't have a vent when you're filling. It'll be OK until the fuel level in the tank is at the top of the fill neck at the tank. It will air lock at that point and you won't be able to fill the tank any further. Maybe that's a lot of lost fuel capacity and maybe it isn't.
Venting while filling is important to how fast you can fill. I suspect that if too much pressure builds while filling or that it 'burps' that this is what shuts off a filler nozzle long before the tank is actually full. My evidence is that if you don't go WOT on the filler lever and fill more slowly that it will fill w/o stopping. It just take one heck of a lot longer.
When I put the new tank in the Valiant I didn't know where 'E' really was. I tried testing it before install and I could not get it to work consistently. Still bugs me about why that was, but.....
So I filled a NATO can and put it and a nozzle in the trunk. Drove it until it sputtered to a stop. Happened that I was coming back from lunch with a co-worker. He always looked at me oddly after that.
Do not disable that vent, you will be putting it back, it is necessary for the tank to fill without giving you a gasoline shower. This is what I installed on the vent, above the tank and below the gas cap. Crude but should give the idea. The vent tank is connected to the vent line on the tank, not the one going to the gas filler. A vent line is attached to the top of the vent tank and routed underneath the truck.
Attachments
I spoke with the tech team at Vapor Trapper earlier this week about my situation. I had “T’d” a vent line to the fuel filler return vent line and then installed the vapor trapper in the rear wheel well, as high as possible. I had the same issue where gas would expand and then flood the VT.
The tech told me that I need to install a gas trap (small check valve) inline before my VT. He also suggested that I move the VT to the engine bay which would add height and plenty of separation between the tank and the VT. He said that the way that I’ve tapped into the existing fuel filler return vent line was very common and acceptable.
The tech told me that I need to install a gas trap (small check valve) inline before my VT. He also suggested that I move the VT to the engine bay which would add height and plenty of separation between the tank and the VT. He said that the way that I’ve tapped into the existing fuel filler return vent line was very common and acceptable.
