Fuel leaking from black rubber in/out pipe holder on fuel tank (MCD Monster)

discusdave

Member
Messages
23
Location
Atlanta, Georgia
Hi guys,
I have some fuel leakage during operation at the black rubber in/out pipe holder on the gas tank.



It is coming from where the cap itself seals to the tank (black rubber to fuel tank), not where the aluminum tubes go in and out. This is the only real source of mess in the truck.

I can replace the cap easily enough, only US $6. Should this solve the issue, or is this a "they all do it" type problem and should I just clean the mess?

And if this is a "they all do it" type problem, can I do anything to seal the cap and tank better, like slicone or something?

Thanks for any help.
Best,
Dave
 

Bigger the Better

LSF Plus Member
PLUS member
Messages
7,738
Location
Minnesota
Sounds to me like you should check to see if on a full tank you just may have too much pressure in the tank causing it to push fuel out of the only release. Do you have a vented cap? You may just add another tube and run it to the rear for venting or get a vented cap. Just guessing, just trying to help.:)
Try posting this one in the MCD are for the MCD pro's.
 
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MONAROMAN

Well-Known Member
Messages
485
Location
Sydney Australia
My MCD doesn't leak there, like btb says, is your tank vented? KCR make a vented cap for the tank or you could make a third hole in the stock grommet and use some fuel tubing to run it outside of the body
 

discusdave

Member
Messages
23
Location
Atlanta, Georgia
Hi guys,
The tank is vented. It is a stock pro-line monster. The gas tank cap is vented, has a barbed brass fitting that some fuel line attaches to. The tubing runs thru the back bulkheads, and attaches to another barbed fitting in a hole in the back right corner of the chassis plate. I checked the tubing/fittings, and the line is clear.

The motor is a CY 30.5 cc stroker. Would a higher displacement motor make more pressure in the tank? I could replace the brass fitting on the gas cap with a wider diameter one and some wider ID tygon tubing and see what that does.

I see the logic of excess pressure blowing fuel out the seal of the in/out rubber pipe holder and the gas tank.

The truck goes like stink, and this is the only issue.
 
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zouz10

Well-Known Member
Messages
1,493
Location
Florida
I got the same problem!! I took it out for a run the other day and there was gas all around the gromet!! It sucks to clean it too. I might put some shoo goo and see what happens.
 

Bigger the Better

LSF Plus Member
PLUS member
Messages
7,738
Location
Minnesota
Sounds like you may want to use a fuel/oil resistant silicone sealant and lightly install some before setting the rubber grommet to the tank. This way it will be possible to remove if needed inthe future. Not sure if shoe goo will be fuel resistant and may disolve into the tank, carb then motor. Auto stores should have a good sealant that should work.

Good luck.:)
 

discusdave

Member
Messages
23
Location
Atlanta, Georgia
Well, I increased the diameter of the vent line from the gas cap and the in/out grommet still leaked. I even loosened the gas tank cap and the grommet leaked, so I do not believe excess pressure is the cause.

I think there is just not a good enough seal between the groove on the side of the in/out grommet and the gas tank, and that it is just the sloshing of the fuel at the grommet/gas tank seal that is the cause of the fuel leaking.

So some automotive type sealant suggested by Bigger the Better is the next thing. I think he hit it on the head And If that doesn't work, maybe a new gas tank.

I am going to order some aluminum bling pieces for the Monster on Monday, so I'll just include a new gas tank if this doesn't work over the weekend.
 

monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
Mine was also a little loose so yesterday I stretched a rubber o-ring into the groove of the grommet and then re-inserted into the tank (which was a real PITA) but now its locked in real tight so should hopefully not leak again.
 
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