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Fuel tank on 1500 ,91 se

2K views 26 replies 9 participants last post by  Aloha Tom 
#1 ·
How is the cap supposed to work,mine always has pressure when removing the cap,with the line from the center of the cap,shouldn't it be vented to the canister?.Seems like when it has pressure after parking that it would put pressure on the fuel system that needs to go somewhere.?
 
#4 ·
fuel always builds up pressure as the temperatures rise.

the fuel system is sealed, it is not vented.

well, mine is, I drilled a hole in the filler neck on my '94SE

not to worry though, EPA don't care....

Mr. Penske's big yellow truck bought that 94SE and took it to a grave yard
 
#5 ·
You can't have a "sealed" fuel system unless you have a regulated bladder controlled system. Period.


There has to be a way to vent the pressure that is built up by heat in our fuel tank so close to the engine or "abnormal" pressure because of elevation or atmospheric conditions. If not you have a ticking time bomb. The fuel would also be forced through the fuel delivery system, into the carbs and wrecking an otherwise delicate carb system.


There also has to be a way to allow air "into" the tank as the tank empties. If not your fuel pump will be fighting a huge vacuum in the tank.


Most gas caps provide a valve system that provides a two way relief system that are set a few PSI in either direction. It will provide a pound or so of pressure if the fuel expanding or a pound or so of vacuum if the fuel is draining.


If you have a California bike, you fuel cap will probably have a hose on it that will go to a carbon filter. Otherwise it will vent a tiny bit into the air.


In newer vehicles the is really evident when you don't screw the gas cap on right and the cap warning light comes on or you get the check engine light. It can't vent or purge it to the charcoal canister.


So is it pressure? Yes. Is it vacuum?? Yes. It all depends on the outside pressure atmospheric pressure vrs the tank pressure.


Common sense.


I myself have had a dirty and sticky fuel cap on a trip. I was loosing power as the tank emptied and loosening the cap while in flight while trying to diagnose it gave INSTANT power and relief. I ended up slicing a couple of very small "V's" into the rubber gasket on the cap to fix the problem until I got home. It worked well enough that I forgot about it for a year or so and was puzzled one day when I discovered tiny "V" groves cut into the rubber.


Tim
 
#8 ·
I just didn't know the numbers.


Tim
 
#7 ·
More info from the internet. You can find anything here. :)

The fuel cap contains an integral pressure and vacuum relief valve. The vacuum valve acts to allow air into the fuel tank to replace the fuel as it is used, while preventing vapors from escaping the tank through the atmosphere. The vacuum relief valve opens after a vacuum of -0.5 psi (3.45 kPa). The pressure valve acts as a backup pressure relief valve in the event the normal venting system is overcome by excessive generation of internal pressure or restriction of the normal venting system. The pressure relief range is 1.6-2.1 psi (11.0-14.5 kPa). Fill cap damage or contamination that stops the pressure vacuum valve from working may result in deformation of the fuel tank.
 
#9 ·
Mine must be in protest,I can open it and I can feel the whoosh in my face,when I fill it to the top and park in the garage,I can smell gas until loosen the cap.
 
#10 ·
If it is capped and then warmed you will get pressure. Even vibration can aggravate the fuel and create pressure.
When you are pumping the gas out obviously you are creating vacuum. If it is capped and warm, then cools it will create vacuum.
When I take my cap off it goes whoosh usually. Hard to tell if it is pressure or vacuum whoosh though. Think they sound the same. I think next time I will hold a match down there to see if the pressure blows it out. :ROFL:>:):ROFL:>:):)
 
#11 ·
When you say you Fill it to the top- are you stopping at the bottom of that indicator bar like the book says to, or are you topping off the tank up to the cap?
If so, thats likely your fuel smell~

Is this a Ca/50 state emission bike?
GURUs!! does the 1500 have a charcoal canister or similar fuel vapor system?
Where does that vent hose go?!

The vent system of the cap may be dirty, soaking cap overnight in Seafoam then blowing vent clear = will resolve many problems
Make sure the vent opening is lined up with the rubber seal
Is the caps rubber seal good?
 
#19 ·
I have just noticed that the fuel cap for 1991 has two different types for GL1500SE A and AC models. I am not quite sure but the difference seems to be the vent hose on the cap as shown below.

How is yours? Does it have a vent hose on it?
Erdiez,
The vent hose on 49 states would go down to the bottom of the bike and open to atmosphere. One state, California has tougher emission regulations that require more equipment. On the CA (California) models the vent hose goes to the charcoal canister where vapors can be stored until such time they can be sent in to the engine to be burned. CA has no vent to atmosphere that doesn't go through the canister.
 

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#21 ·
This is the type mine is,mine is defiantly a whoosh of pressure outward.
 
#27 ·
I did not see an answer to How Full is full from the OP of this thread?

on Honda cars, if you `overfill` the tank you can get raw fuel in the charcoal canister, which it does not like at all. Clogged canister causes many problems
Technology transfer to the bikes??

I asked if its a 50 state bike for that reason, different vac systems- but who knows where a bike was destined,,,compared to current home.
Many Ca spec bikes are wandering America and other countries these days.
Where is the decal saying smog spec??
 
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