Is gas tank cap vented?, tank cap |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Is gas tank cap vented?, tank cap |
tomrev |
Jan 9 2016, 02:35 PM
Post
#1
|
Member Group: Members Posts: 231 Joined: 25-February 14 From: N. Mich. Member No.: 17,037 Region Association: None |
As I am finishing up new fuel lines, with clean, empty tank, it seems like the tank holds a slight pressure, when blowing thru the return line. I'll be using the bosch 044 fuel pump, which moves a lot of fuel, and want to make sure there is no pressure fighting the flow back to the tank. Does the stock '75 cap have any self venting property's, or does all the tank venting go thru the TINY vent port, that heads to the charcoal canister? If so, have any of you added a bigger vent, as a fuel cell would use? Thanks, Tom
|
damesandhotrods |
Jan 9 2016, 02:59 PM
Post
#2
|
Senior Member Group: Members Posts: 568 Joined: 26-September 10 From: Santa Cruz California Member No.: 12,218 Region Association: Northern California |
The fuel tank vents to atmosphere through the charcoal canister, and only the charcoal canister. The cap is not vented.
|
tomrev |
Jan 9 2016, 03:11 PM
Post
#3
|
Member Group: Members Posts: 231 Joined: 25-February 14 From: N. Mich. Member No.: 17,037 Region Association: None |
|
whitetwinturbo |
Jan 9 2016, 03:36 PM
Post
#4
|
Honey, does this wing make my ass look fat? Group: Members Posts: 1,391 Joined: 22-October 11 From: Newport Beach/Kalefornya/USA Member No.: 13,704 Region Association: Southern California |
..........so how does fuel tank vent if there is no canister?
|
TheCabinetmaker |
Jan 9 2016, 03:50 PM
Post
#5
|
I drive my car everyday Group: Members Posts: 8,301 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
|
tomrev |
Jan 9 2016, 04:09 PM
Post
#6
|
Member Group: Members Posts: 231 Joined: 25-February 14 From: N. Mich. Member No.: 17,037 Region Association: None |
..........so how does fuel tank vent if there is no canister? It vents into the cockpit so you can smell it. Or down, and thru the lower pan, to the road. Still can't believe that pin hole sized vent can keep the internal pre. the same as ext. I guess it's worked this long, eh? |
Rob-O |
Jan 10 2016, 05:01 PM
Post
#7
|
Senior Member Group: Members Posts: 1,252 Joined: 5-December 03 From: Mansfield, TX Member No.: 1,419 Region Association: Southwest Region |
|
Blue6 |
Jan 10 2016, 05:48 PM
Post
#8
|
Senior Member Group: Members Posts: 1,035 Joined: 3-October 13 From: SoCal Member No.: 16,470 Region Association: Southern California |
..........so how does fuel tank vent if there is no canister? It vents into the cockpit so you can smell it. Wow, soooo true! (IMG:style_emoticons/default/biggrin.gif) |
damesandhotrods |
Jan 10 2016, 05:52 PM
Post
#9
|
Senior Member Group: Members Posts: 568 Joined: 26-September 10 From: Santa Cruz California Member No.: 12,218 Region Association: Northern California |
..........so how does fuel tank vent if there is no canister? If there is no canister plumbed, than you have to add a vent. If you do not add a vent you won’t smell gas fumes, your engine will stop running at very inopportune times and places. And don’t expect a couple of feet length of hose in a loop to work as a vent either… |
JeffBowlsby |
Jan 11 2016, 01:53 AM
Post
#10
|
914 Wiring Harnesses Group: Members Posts: 8,524 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None |
Actually there is an expansion tank in the pathway...not just the charcoal filter.
Attached image(s) |
whitetwinturbo |
Jan 11 2016, 11:00 AM
Post
#11
|
Honey, does this wing make my ass look fat? Group: Members Posts: 1,391 Joined: 22-October 11 From: Newport Beach/Kalefornya/USA Member No.: 13,704 Region Association: Southern California |
.........where is that "expansion" tank?
|
Kansas 914 |
Jan 11 2016, 12:13 PM
Post
#12
|
Advanced Member Group: Members Posts: 2,999 Joined: 1-March 03 From: Durango, Colorado Member No.: 373 Region Association: Rocky Mountains |
|
76-914 |
Jan 11 2016, 03:37 PM
Post
#13
|
Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,507 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California |
Need one? I've got one left over from my conversion.
|
damesandhotrods |
Jan 11 2016, 06:05 PM
Post
#14
|
Senior Member Group: Members Posts: 568 Joined: 26-September 10 From: Santa Cruz California Member No.: 12,218 Region Association: Northern California |
As I am finishing up new fuel lines, with clean, empty tank, it seems like the tank holds a slight pressure, when blowing thru the return line. I'll be using the bosch 044 fuel pump, which moves a lot of fuel, and want to make sure there is no pressure fighting the flow back to the tank. Does the stock '75 cap have any self venting property's, or does all the tank venting go thru the TINY vent port, that heads to the charcoal canister? If so, have any of you added a bigger vent, as a fuel cell would use? Thanks, Tom The gas tank vent is designed to prevent a vacuum from building up in the fuel system, and as a smog device to control gas vapors. If your tank is pressurized you have got a different problem to solve. Carbs are a low pressure fuel system; you should not have any pressure in the tank… |
tomrev |
Jan 11 2016, 06:22 PM
Post
#15
|
Member Group: Members Posts: 231 Joined: 25-February 14 From: N. Mich. Member No.: 17,037 Region Association: None |
The gas tank vent is designed to prevent a vacuum from building up in the fuel system, and as a smog device to control gas vapors. If your tank is pressurized you have got a different problem to solve. Carbs are a low pressure fuel system; you should not have any pressure in the tank… This was based on my blowing thru the return line, into an empty tank, thru a -6 line. I think it builds a little back pressure because the vent tube is only about 1/16th in. diameter inside the tube. I will be running high pre. injection, not carbs. I suppose the pump is pulling more volume out of the tank, than the return line is putting in when running. Comparing it to a fuel cell, with a -6 (3/8 in.) ID vent line, where there is no resistance,it seemed odd. Will see how it runs. |
Lo-Fi Version | Time is now: 1st June 2024 - 06:57 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |