March 28, 2024, 04:50:14 PM

Author Topic: Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?  (Read 3495 times)

Offline halfspec

Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?
« on: June 05, 2012, 06:59:29 PM »
Ok. I've searched and seen that this topic has been touched on a couple of times here, but no-one has really addressed exactly what I'm looking for.

I recently realized that my fuel system is sealed. I remembered that when I dropped my gas tank I saw that the two vents were connected together with a piece of heater hose / fuel hose. At the time I didn't really think anything of it, but the memory remained. The other day I ran across a thread talking about keeping some type of tank vent in-tact for proper operation and it really got me thinking. I checked the gas cap and found that it was not vented, so with the sealed top vents and an non-vented cap, I'm assuming I've been trying to run my car with a sealed tank which probably means my fuel pump has been working overtime and it may explain why my fuel pressure climbed ~ 10psi (different gas cap positions maybe (more sealed / less sealed)) a few months back (I haven't run the car since). Anyway... My car's been in the paint shop for a lot time and now that it's out I'm trying to figure out why it runs rough and I can't help but think that this may be negatively impacting my engine's operation.

So... I'm looking for the best solution. When I thought this through last weekend I did the first thing that came to mind and ordered a little vented Stant fuel cap:

http://www.amazon.com/gp/product/B000B8JULG/ref=oh_details_o05_s00_i00

Fits and looks great. Should be ok with this even though the tank vents are plugged right? Only con is that I may smell a little gassy right?

Is there a better solution? Should I try and rebuild the stock system with a charcoal canister, or make some type of safe vent without a charcoal canister using check valves that connect to the tank vents?

Any feedback is appreciated :)

Lane

Offline mayhamfx

Re: Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?
« Reply #1 on: June 05, 2012, 07:12:34 PM »
All I know is I left the charcoal canister hooked up to the tank and then ran a line with a check valve (venting pressure out) to the air intake tube after the MAF and before the TB. Who knows what actually happens but my logic is if pressure builds in the tank it will vent into the intake stream and be burnt off. I doesn't seem to affect anything and I have never smelt gas.
90 Vert 5.3 / T-5   Back on the road.
"To save time let's just assume I know everything!"
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Offline priceless

Re: Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?
« Reply #2 on: June 05, 2012, 08:23:51 PM »
That topic was about my car.  I dont know if the stant is vented or not, most the gas caps I found were push to vent.  I dont have the charcoal canister either.  Atleast your lines were attached and no fuel came out.

What I did was I got a push to vent gas cap, and I modified it.  I took out the plunger and spring so its now vented. I also pugged the two fuel vapor valves. Got the cap at Oreilly.  I havent tried it yet to see how it smells (since the weather has been shitty). I did take out almost 8 gallons of gas since I had just filled it up.  Im gonna try to take it out tonight as long as its not raining.

Question still that bothers me is WHY would someone do what was done to my car? There was no need to remove the seperator. 
2005 Mercedes E320 CDI
2005 Subaru Baja
1993 Mazda RX7 (sold) :(

Offline halfspec

Re: Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?
« Reply #3 on: June 05, 2012, 08:34:37 PM »
Thanks for the info guys. Yes priceless. I do believe it was your thread that sparked the question in my mind. Thanks for posting  :cheers:

I ordered the Stant cap specifically because it was listed as being vented. Amazon doesn't do a good job listing specs, but other sites do:

http://www.autopartswarehouse.com/sku/Stant/Gas_Cap/ST10817.html

I just use Amazon because I'm a prime member and I get just about everything with free 2nd day shipping  :drive:
I admit, its design does make me skeptical though since it looks like a pretty normal cap. I did a 'suck' test by basically sucking on the threaded / tank side of the cap but I haven't tried to blow it yet haha! Sucking in air seems to be no problem, which is what I was worried about since I thought the fuel pump may have a problem, at least initially, sucking gas out of a tank that isn't vented (yes, I know that the fuel return evens things out, but not completely). I figured having a vent that would allow air to flow in would make it easier for the pump to pump fuel out (kinda like the bleed plug on a gas can). Having pressure accumulate in the tank wasn't on my mind yesterday. I'll have to check to make sure the Stant cap can flow both ways tonight.

Since nobody is throwing up any red flags I guess I'm just going to proceed as I am (tank vents plugged) after verifying that the cap flows both ways.

Lane

Offline digitalsolo

Re: Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?
« Reply #4 on: June 05, 2012, 08:36:19 PM »
FWIW, I have a specific vent on my tank.  -8 AN check ball (rollover valve) that runs to a -8 line out the back of the car.   The secret is that the line has a 360 bend in it, so that vapor/fuel does not leak out.

A vented gas cap will work fine also, or you can make the system work as factory.
Blake MF'ing McBride
1988 Mazda RX7 - Turbo LS1/T56/ProEFI/8.8/Not Slow...   sold.
1965 Mustang Coupe - TT Coyote, TR6060, modern brakes/suspension...
2007 Aston Martin V8 Vantage - Gen V LT4/TR6060, upper/lower pullies, headers, tune.
2021 Tesla Model 3 Performance - Stock...ish.

Offline mefarri

Re: Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?
« Reply #5 on: June 05, 2012, 11:29:30 PM »
Why not leave the sealed cap, and use the vent(s) on the tank to go into a charcoal canister that is ultimatly vented to atmosphere?
"I'm not sure what your intent was because I don't speak "dumbshit", but next time, start your own thread. "

-Jimlab

"Otherwise it looks like something I can build over a weekend, if I spent the first day watching TV."

-Blake motherfucking McBride

Offline halfspec

Re: Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?
« Reply #6 on: June 05, 2012, 11:42:36 PM »
Ah. I forgot to mention. My roller didn't come with any of the emissions equipment, which is the source of my issue. It only came with a piece of hose that loops the tank vents. No charcoal canister for me. I guess I could replicate the system using used parts sourced on the club though. One of the reasons I posted was to ask in a roundabout way if one method is more advantageous than the others. If retaining the charcoal canister is really the best way to do things than I’ll see about obtaining and installing it.
Lane

Offline priceless

Re: Tank Venting Charcoal, Filter, Check Valve, or Vented Cap?
« Reply #7 on: June 07, 2012, 04:38:52 PM »
Ah. I forgot to mention. My roller didn't come with any of the emissions equipment, which is the source of my issue.

Mine didnt either.  The vented cap seemed to work fine for me.  No issues.  If you could source the canister and seperator it would be the best way, but the vented cap just fine.  If you have smog though, you might want to keep the other cap and put it on when its smog time.  They test the caps in cali, not sure about here, buts thats what ill do.
2005 Mercedes E320 CDI
2005 Subaru Baja
1993 Mazda RX7 (sold) :(