Reply
 
Thread Tools Display Modes
 
Old 05-09-2015, 03:01 PM   #1
Skoolie
 
Join Date: Mar 2015
Posts: 231
fuel filler cap

Are the filler caps supposed to be vented?

I am asking because my bus came with out the filler cap, I have it covered with a rag and tape and it is inside the door.
I was wondering if a regular pipe cap would work or if I need to go to a truck dealer to get a replacement.

thanks
c_hasbeen is offline   Reply With Quote
Old 05-09-2015, 09:35 PM   #2
Site Team
 
crazycal's Avatar
 
Join Date: Feb 2007
Location: NUNYA
Posts: 4,233
Year: 1995
Coachwork: Thomas
Chassis: 3800
Engine: DT408, AT545
Rated Cap: 23 500 gvw
Mine are brass. You might be able to pick one up at a truck parts place.
__________________
I'm hungry!

You Gotta Let Me Fly
crazycal is online now   Reply With Quote
Old 05-09-2015, 09:54 PM   #3
Bus Nut
 
Alan N's Avatar
 
Join Date: Jan 2015
Location: Gonvick MN
Posts: 330
Year: 1975
Chassis: Gillig
Engine: Cat 3208t/10 speed transmission
Quote:
Originally Posted by c_hasbeen View Post
Are the filler caps supposed to be vented?

I am asking because my bus came with out the filler cap, I have it covered with a rag and tape and it is inside the door.
I was wondering if a regular pipe cap would work or if I need to go to a truck dealer to get a replacement.

thanks
Your tank is most likely vented.
A pipe cap will work fine.
__________________
Remove hence to yonder place....
Alan N is offline   Reply With Quote
Old 05-09-2015, 10:02 PM   #4
Bus Nut
 
superdave's Avatar
 
Join Date: Mar 2015
Location: hills of sw virginia
Posts: 889
Year: 1996
Chassis: thomas
Engine: 8.3 cummins
Rated Cap: 11 window
my cap has real fine threads, not npt. be carefull not to ruin the threads with the wrong thread.
__________________
living in a bus down by the river.
my build pics
https://www.skoolie.net/forums/membe...albums942.html
superdave is offline   Reply With Quote
Old 05-10-2015, 09:04 AM   #5
Skoolie
 
Join Date: Mar 2015
Posts: 231
yea these do actually look fine threads. I will go talk to them at kenworth on Tuesday
c_hasbeen is offline   Reply With Quote
Old 05-10-2015, 09:12 AM   #6
Bus Geek
 
Join Date: Aug 2011
Location: Stony Plain Alberta Canada
Posts: 2,937
Year: 1992
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: 190hp 5.9 Cummins
Rated Cap: 72
I wish you lived closer. We have a ton of scrap buses. I could have given you a fuel filler cap.

Nat
__________________
"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."

Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization
nat_ster is offline   Reply With Quote
Old 05-10-2015, 10:40 AM   #7
Skoolie
 
Join Date: Mar 2015
Posts: 231
Quote:
Originally Posted by nat_ster View Post
I wish you lived closer. We have a ton of scrap buses. I could have given you a fuel filler cap.

Nat

The funny thing is I called the guy who I bought this from because he said he had a bunch of old scrap buses but he would not go look for one.

I will find one close by, I am sure
c_hasbeen is offline   Reply With Quote
Old 05-10-2015, 08:23 PM   #8
Bus Nut
 
superdave's Avatar
 
Join Date: Mar 2015
Location: hills of sw virginia
Posts: 889
Year: 1996
Chassis: thomas
Engine: 8.3 cummins
Rated Cap: 11 window
i stand corrected, my 96 thomas gas cap is 2" npt, no vent stamped on it.
__________________
living in a bus down by the river.
my build pics
https://www.skoolie.net/forums/membe...albums942.html
superdave is offline   Reply With Quote
Old 05-10-2015, 08:42 PM   #9
Bus Crazy
 
Join Date: Jul 2011
Location: Winlcok, WA
Posts: 2,133
Short answer, some are and some are not vented.

Putting a vented cap on a tank that is vented can cause some issues.

Putting a non-vented cap on a tank that is not vented can cause other issues.

Just make sure you put the correct one on as it does make a difference.

Also be aware, some are male thread and some are female thread.
cowlitzcoach is offline   Reply With Quote
Old 05-11-2015, 07:30 AM   #10
Bus Geek
 
bansil's Avatar
 
Join Date: Nov 2011
Location: MNT CITY TN
Posts: 5,158
crawl under bus and look at tank, see if there is a rubber line coming from top of tank and draped over the side, I have actually pressurized my tank to a couple pounds using a tapered plastic fitting for inner tubes and air mattresses, stuck in that vent hose when filling new filters and bleeding injector lines (do not over pressurize!!!)
__________________
Our build La Tortuga
Accept the challenges so that you can feel the exhilaration of victory.
George S. Patton
bansil is offline   Reply With Quote
Old 05-11-2015, 07:40 AM   #11
Bus Nut
 
Join Date: Dec 2014
Location: Florida
Posts: 584
Year: 1988
Coachwork: Blue Bird
Chassis: I.H.
Engine: DT360
Quote:
Originally Posted by bansil View Post
crawl under bus and look at tank, see if there is a rubber line coming from top of tank and draped over the side, I have actually pressurized my tank to a couple pounds using a tapered plastic fitting for inner tubes and air mattresses, stuck in that vent hose when filling new filters and bleeding injector lines (do not over pressurize!!!)
As I read the first portion, I thought you were talking about filling inner tubes and air mattresses from the gas fumes in the tank. I can picture that. Not good.:icon_e_surprised: Glad you clarified.
HolyBus is offline   Reply With Quote
Old 05-11-2015, 10:06 AM   #12
Bus Geek
 
bansil's Avatar
 
Join Date: Nov 2011
Location: MNT CITY TN
Posts: 5,158
:icon_e_ugeek:

what is this emoticon?

A geeky, colored glasses goatee wearing...HippY , or maybe a techy guy ????


still kind of cool, so I will use it....Random-ness interwebz.....rowdy-ness


__________________
Our build La Tortuga
Accept the challenges so that you can feel the exhilaration of victory.
George S. Patton
bansil is offline   Reply With Quote
Old 05-12-2015, 06:23 PM   #13
Skoolie
 
Join Date: Mar 2015
Posts: 231
I was not able to find a tube hanging over the side of the tank, i called a couple of truck places here in town but they had no reference book.
I put a regular pipe cap on it.

If it is supposed to be vented cap will I notice a vacuum if it is running and I hold my hand over the tube?
maybe a piece of plastic bag?
thanks
Cliff
c_hasbeen is offline   Reply With Quote
Old 05-12-2015, 10:33 PM   #14
Bus Crazy
 
Join Date: Jan 2008
Location: Adirondack Mountains NY
Posts: 1,099
Quote:
Originally Posted by c_hasbeen View Post
. . . I put a regular pipe cap on it.

If it is supposed to be vented cap will I notice a vacuum if it is running and I hold my hand over the tube?
maybe a piece of plastic bag?
thanks
Cliff
If it is supposed to be vented but is not, I don't think the fuel draw will be fast enough to feel suction on your hand, but I may be wrong. But once the engine pumps enough fuel out, there will usually be a vacuum that will prevent drawing any more and seem like you ran out of fuel.

As a result, you open the cap and see there is indeed fuel, put the cap back on and voila!, the engine starts and runs again until it doesn't. My snowblower lost a vent spacer in its cap this winter, and with the cap on tight it was pulling this trick until I figured it out.

On the sheet metal passenger car tanks, I have heard that with a strong enough fuel pump the vacuum can collapse the tank instead of starving the engine. But the heavy tank on a bus should be strong enough to resist this.

If the engine will run for an hour with the un-vented pipe cap on the tank, you should not need to add a vent and be good to go.

If you have any doubts, a pinhole in the pipe cap would relieve the vacuum. I'm guessing that 1/8 inch or even smaller might do the trick. I would maybe even start with 1/16 inch. If the bus idles and cruises fine, but seems to starve going up long hills unless you take your foot off the throttle, you might gradually enlarge the vent until you have continuous power at all loads.
__________________
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.
Redbear is offline   Reply With Quote
Old 05-13-2015, 06:14 AM   #15
Bus Geek
 
bansil's Avatar
 
Join Date: Nov 2011
Location: MNT CITY TN
Posts: 5,158
Sounds like great advice Redbear
__________________
Our build La Tortuga
Accept the challenges so that you can feel the exhilaration of victory.
George S. Patton
bansil is offline   Reply With Quote
Old 05-17-2015, 08:11 AM   #16
Bus Crazy
 
Join Date: Jan 2008
Location: Adirondack Mountains NY
Posts: 1,099
I forgot to add that the effect is greater when the tank is full of fuel, and not nearing empty. If a vacuum is formed, a near-empty tank would try to expand a lot of air just a little bit, and may not cause fuel starvation.

A vacuum caused in a near-full tank would need to expand the little bit of air a lot, and cause a multiplication of the pressure drop and its effects.
__________________
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.
Redbear is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 03:22 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×