R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Nitro Off-Road

Reply
 
Thread Tools Search this Thread
Old 08-26-2008, 08:52 AM   #1
Tech Master
 
hobdog's Avatar
 
Join Date: Jul 2008
Location: Albany, OR.
Posts: 1,028
Trader Rating: 19 (100%+)
Default air bubbles in the fuel line

I have run into a issue on my mbx5t. I am not running any fuel filters at the moment (not sure if there is one in the tank on these truggys). I just switch the fuel line to make it longer (put two loops of fuel line) and I am getting alot of air bubbles in the fuel line. When I go to start it, it will run and then sometimes shut off because of the air bubbles. At times it will shut off out of no where on the track, and when I look at it there will be air bubbles in the line. I have checked that tank for air leaks, and the lines and all seems good. I got to get this figured out, I have a race this weekend and the truck is running great besides the flame outs.
hobdog is offline   Reply With Quote
Old 08-26-2008, 09:34 AM   #2
Tech Master
 
RC Dad's Avatar
 
Join Date: Jun 2007
Location: Bismarck
Posts: 1,355
Trader Rating: 26 (100%+)
Send a message via MSN to RC Dad
Default

If the fuel line is more than a year old, replace it. If it's fresh, nip off one inch from each end of your fuel line and try again. The stretching that occurs when you pull the line on and off the nipple is frequently the culprit when you get air bubbles as it weakens the tubing near the end. Try to help it off the nipple by pushing gently with a screwdriver while pulling.
__________________
GV2 Pro, XXX4G+, Blitz SCT, CRC GenXL
RC Dad is offline   Reply With Quote
Old 08-26-2008, 09:49 AM   #3
Tech Elite
 
AssocRacer's Avatar
 
Join Date: May 2005
Location: Greenfield, WI
Posts: 2,295
Trader Rating: 9 (100%+)
Send a message via AIM to AssocRacer Send a message via Yahoo to AssocRacer
Default

Fuel line is cheap, i'd say get more...but you don't need a whole lot of fuel line. Long fuel lines can be very hard to get rid of air bubbles once they are there. I would make the fuel lines shorter. Longer fuel lines usually doesn't equal longer run times. Also, i'm not so sure i'd be running without at least one fuel filter. Most of the guys i run with (including myself) run 2 filters. That's where you're gonna get your extra run time.
__________________
Lots O' Planes
AssocRacer is offline   Reply With Quote
Old 08-26-2008, 10:12 PM   #4
Tech Master
 
hobdog's Avatar
 
Join Date: Jul 2008
Location: Albany, OR.
Posts: 1,028
Trader Rating: 19 (100%+)
Default

well I will try everyones suggestions tommorow. I shorten up the fuel line and trimmed the ends. As far as the fuel filter goes, I have heard that they are prone to causing air bubbles. I definitely need one if my gas tank does not have one in it. Does anyone know if the mbx5t tank has a built in filter?
hobdog is offline   Reply With Quote
Old 08-26-2008, 11:31 PM   #5
Tech Adept
 
TRArena's Avatar
 
Join Date: Mar 2008
Posts: 155
Default

make sure the screws fixing your tank are not too tight. If the tank can not 'wobble' freely on its mounts it can cause bubbles in the fuel line.
TRArena is offline   Reply With Quote
Old 08-27-2008, 01:08 AM   #6
Tech Elite
 
razzor's Avatar
 
Join Date: Aug 2005
Location: Durban, South Africa
Posts: 2,810
Default

No matter what you do you will get air bubbles in your fuel line especially when running.
Your fuel gets airated from the sloshing in the tank.
Always good to have your fuel line about 8/9 inches long and/or have a inline filter or reservoir.
Double check fuel line for any leaks or split ends and then look at maybe picking up idle or check bottom end tune.
__________________
Casterracing ZX1.5R
casterracing EX-1 Pro, SP Silver Arrow
TOP Racing Scythe, SP 17.5, SP GT Pro 2.0
TOP Racing Scythe, SP 4.5 V2, Hobbywing Xerun 120SD 2.0
TOP Racing Scythe, SP 13.5, Hobbywing Xerun 120SD 2.0
razzor is offline   Reply With Quote
Old 08-27-2008, 01:30 AM   #7
Tech Master
 
pitpop's Avatar
 
Join Date: Mar 2006
Posts: 1,445
Default

there shouldn't be air in the fuel line... these kinds of problems can drive you nuts, but it sounds to me like a tank issue

normally this is caused by the tank.. if your fuel line is good, it's the only other thing it could be

we run a filter, and it doesn't cause any problems... sometimes it traps air after sitting in your pit, but with a few minutes of running, all the air gets pushed out

I tip the car back to get the air out during warm up.
__________________
Cody King's Wrench (and dad :))| Team Kyosho International | Reds Racing Engines | Pro-Line Tires
KO Propo | Byron Fuels | AbsoluteHobbyz.com | Stickit1 Racing | kustomrcgraphics.com
LiveRC.com | OCRC Raceway | codykingrc.com | ROAR Sanctioning Director
pitpop is offline   Reply With Quote
Old 08-27-2008, 01:43 AM   #8
Tech Addict
 
IanWright's Avatar
 
Join Date: Dec 2007
Location: If i'm not in England i'm in Southern California
Posts: 532
Trader Rating: 1 (100%+)
Send a message via AIM to IanWright
Default

Take out your tank and use fresh fuel line, dunk the tank in a bucket of water, pinch one end of the fuel line and blow into the other length. If you see bubbles you have a crack in the tank. If not and a change of fuel line doesn't do it... ummmm... erm... i am out of ideas!
IanWright is offline   Reply With Quote
Old 08-27-2008, 01:56 AM   #9
Tech Adept
 
David Day's Avatar
 
Join Date: Nov 2007
Location: Lake Havasu City, Arizona
Posts: 128
Trader Rating: 4 (100%+)
Send a message via AIM to David Day Send a message via MSN to David Day Send a message via Yahoo to David Day
Default

Quote:
Originally Posted by IanWright View Post
Take out your tank and use fresh fuel line, dunk the tank in a bucket of water, pinch one end of the fuel line and blow into the other length. If you see bubbles you have a crack in the tank. If not and a change of fuel line doesn't do it... ummmm... erm... i am out of ideas!
+1
__________________
Day Brothers Racing
*http://daybrosracing.webege.com*
2nd Place 2006 Winter Series 10th/Scale Gas @ Lake Havasu RC Raceway
RC10GT - Snoopy #5x
Kyosho Inferno777 WC SP2
David Day is offline   Reply With Quote
Old 08-27-2008, 02:22 AM   #10
Tech Master
 
pitpop's Avatar
 
Join Date: Mar 2006
Posts: 1,445
Default

sorry guys, but that won't tell him anything

if the pick up is sucking air, it can do it inside the tank, and there will be bubbles in the fuel line, even if the tank it air tight

just bite the bullet, and get a new tank, sometimes they are bad
__________________
Cody King's Wrench (and dad :))| Team Kyosho International | Reds Racing Engines | Pro-Line Tires
KO Propo | Byron Fuels | AbsoluteHobbyz.com | Stickit1 Racing | kustomrcgraphics.com
LiveRC.com | OCRC Raceway | codykingrc.com | ROAR Sanctioning Director
pitpop is offline   Reply With Quote
Old 08-27-2008, 02:31 AM   #11
Tech Champion
 
asw7576's Avatar
 
Join Date: Sep 2004
Posts: 5,792
Default

There is always bubble situation within fuel lines. You can minimize the bubbles occurance with inline fuel filter within the fuel line.

Don't worry so much about fuel bubbles as long as your engine is running perfectly.
__________________
On Road : Xray NT1 , RX8 , T4 || Mugen Seiki MRX4-R , MTX4 , MTX3 prospec || Tamiya M03 , M04 || Top Racing Sabre FD2
Off Road : Xray XT8 || Hobao Hyper 8
Radio : Futaba 3PKS || KO propo EX-10 eurus
asw7576 is offline   Reply With Quote
Old 08-27-2008, 06:24 AM   #12
Tech Elite
 
DOMIT's Avatar
 
Join Date: Oct 2007
Location: Fort Worth, Texas, USA, North America, Earth, Solar System, Milky Way Galaxy, Universe
Posts: 4,034
Trader Rating: 1 (100%+)
Send a message via MSN to DOMIT Send a message via Yahoo to DOMIT
Default

I was fighting this problem last week... replaced the tank, no dice... replaced line, shortened line, nothing helped. It would go normal lean normal fat lean tune was all over the place, couldn't get it to behave.

Then I pulled my carb off and re-sealed it with silicone. Problem solved.

I have no idea WHY, but it was a suggestion from my bud and it worked.
__________________
Brad "DOMIT" Smith - I'm not fast, but at least I wreck a lot.
Unsponsored, but I use/recommend: XRay XB9, Alpha A852, Dynamite 053, Airtronics M11, Hitec 5955TG & 7955TG, ABEC 35 clutch and chassis bearings, PTRCRacing shock and diff fluids, Ready Rollers ceramic engine bearings. ** Team Terribles Region 9 coordinator. ** JOIN TEAM TERRIBLES! All racers welcome! PM me for details.
DOMIT is offline   Reply With Quote
Old 08-27-2008, 06:31 AM   #13
Tech Lord
 
wingracer's Avatar
 
Join Date: Nov 2007
Posts: 12,785
Trader Rating: 23 (100%+)
Default

A loose or leaking banjo fitting (the nipple on the carb under the HSN) can cause all kinds of bubbles.
__________________
Sean. Certified speed crazed mowron.
Team Shepherd USA
www.ashfordhobby.com
wingracer is offline   Reply With Quote
Old 08-27-2008, 09:19 AM   #14
Tech Master
 
pitpop's Avatar
 
Join Date: Mar 2006
Posts: 1,445
Default

coming from the tank?
__________________
Cody King's Wrench (and dad :))| Team Kyosho International | Reds Racing Engines | Pro-Line Tires
KO Propo | Byron Fuels | AbsoluteHobbyz.com | Stickit1 Racing | kustomrcgraphics.com
LiveRC.com | OCRC Raceway | codykingrc.com | ROAR Sanctioning Director
pitpop is offline   Reply With Quote
Old 08-27-2008, 10:11 AM   #15
Tech Apprentice
 
Twitchy Kanai's Avatar
 
Join Date: Jun 2008
Location: Oklahoma City, Oklahoma
Posts: 79
Trader Rating: 9 (100%+)
Send a message via MSN to Twitchy Kanai
Default

Air bubble(s) will not flow in opposite direction of fuel flow.

I also have air bubbles that I can't get rid of. Bubbles are not big they are very tiny but it still bothers me enough that I've tried several new tanks and several feet of new lines and the bubbles are still there.
Twitchy Kanai is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
SAVAGE - SS, .25, .21 Official Thread! Horatio Monster Trucks 11167 05-15-2017 08:40 PM
GRP... Engine... Thread... xlgraphicspro Offroad Nitro Engine Forum 2135 09-10-2013 08:46 AM
Jammin X1 - so close yet so far beetlebz Nitro Off-Road 4524 03-25-2012 01:54 PM
Trinity EXTECH .21 Fierle03 Offroad Nitro Engine Forum 2130 06-09-2011 07:01 AM
Stalling when low on fuel. sperera Nitro Off-Road 19 09-08-2009 10:26 PM
air leak? ruggydriver Nitro Off-Road 7 10-18-2008 12:19 AM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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 On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 07:11 PM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net