[GMCnet] Vapor Canister

[Dolph Santorine]

Hi All:

Do the vapor canisters go bad? What kind of resistance should I see with pressure or vacuum on the tank or carb ports?

Should I replace it?

FWIW, the vapor hose up by the fuel entry (in the wheel well) was not ethanol friendly. It literally looked like the "soaker hose" that my wife uses in the garden. It was fairly obvious that the material was attacked from the inside out.

Input would be appreciated.


Dolph
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[James Hupy]

Dolph, "ever go bad" is not a definitive statement. Charcoal probably not,
the plastic canister almost certainly. The fumes from alcohol blended
gasoline are in some cases more corrosive than liquid if you figure
nitrogen/oxygen into it. Those vent hoses should be bad by now if they are
original. If there is evidence of liquid fuel in the canister, check your
liquid/vapor separator in the driver's side rear wheel well.
Jim Hupy
Salem, Or
78 Gmc Royale 403

[gene Fisher]

since your are in Wash

read this
http://gmcmotorhome.info/engine.html#canister

this is what I am going to do in Orgn.

remove the line at the liquid separator
and install a new one
run the exit hose down so any vapor goes behind the wheels and away from
the exhaust


jwid
gene

On Sun, Nov 18, 2012 at 4:30 PM, Dolph Santorine
<do...@dolphsantorine.com>wrote:

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[gene Fisher]

On Sun, Nov 18, 2012 at 4:50 PM, gene Fisher <mr.er...@gmail.com> wrote:

> since your are in Wash
>
> read this
> http://gmcmotorhome.info/engine.html#canister
>
> this is what I am going to do in Orgn.
>
> remove the line at the liquid separator

> and install a new separator, one

[Emery Stora]

Gene

Mine has been that way for about 10 years now.

Emery Stora

[mr.er...@gmail.com]

Great message

There should be nothing plugging. The vents

Tanks
Gene

FREE WIFI @ Mickey D

[Steven Ferguson]

JWID also.

--
Fathom the hypocrisy of a nation where every citizen must prove they have
health insurance......but not everyone has to prove they're a citizen.
Steve Ferguson
Sierra Vista, AZ

[gene Fisher]

thanks

going for it.

there is no reason to have pressure or vacuum in the gas tanks

there are 3/4 in. of vents in each tank.
- you should be able to fill at max pump rate
- you should never get pressure when you remove the cap

if you have either of these issues, you have vent problems
- crushed hoses
- bad liquid separator
- bad canister system

http://www.gmcmhphotos.com/photos/data/4634/TANK_VENTS1.pdf

more later
gene
-

[Bruce Hislop]

Is there any reason not to hook it up properly?

It provides a way to trap and use fuel that has vaporized and would otherwise be lost.

A PO had disconnected and plugged the hose to the carb on mine. When I re-hosed the fuel system, I renewed the hosing to the liquid separator and the canister. I have EFI with the EBL which will control the canister purge so I got a solenoid valve from a Jeep Cherokee. I haven't got around to installing it yet but its on the list!

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

[gene Fisher]

>
> Is there any reason not to hook it up properly?
>

only if you make it work

problems
- if you have pressure in the tank while driving
- rust in the lines to the canister
- vacuum leak to the engine (connection to the canister)
- plugged liquid separator
- rubber lines to the tank vent connections (long and winding)
- corrupted canister contents ( full of something)
- gas leaks on the top of the tanks

AS ALWAYS
If It Works, Don't Fix It

IIWDFI

gene

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Matt Colie]

rf_burns wrote on Mon, 19 November 2012 08:08

> Is there any reason not to hook it up properly?
>
> It provides a way to trap and use fuel that has vaporized and would otherwise be lost.
>
> A PO had disconnected and plugged the hose to the carb on mine. When I re-hosed the fuel system, I renewed the hosing to the liquid separator and the canister. I have EFI with the EBL which will control the canister purge so I got a solenoid valve from a Jeep Cherokee. I haven't got around to installing it yet but its on the list!

Bruce,

It is a real good idea to make it work if you have EFI. The vapor that does get pulled in will >replace< liquid fuel from the tank and the O2 sensor will keep the mixture correct. This is where the early catalyst cars used to fall on there face.

Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will find
SE Michigan - Twixt A2 and Detroit

[Dolph Santorine]

I know it's an old thread, but I finally had a chance to do a little research.

First, the activated carbon material generally does not degrade unless it's been under water (clogged with dirt/silt).

The canister material is not attacked by Ethanol. It's a polyethylene blend (thanks milk jugs).

So, if your canister is not leaking charcoal, it's top and bottom filters are probably OK. Blow some low pressure air (less than 40 psi) into the inlet. The inlet and or exit (to carb) fittings may have a check valve or be clogged. A little brake cleaner may get it free.

I ran mine with a vacuum pump for a while. It does exactly what you would expect it to do.

I replaced the bottom filter, that I was able to get at the local Advance Auto parts (they have exactly two counter people who I will talk to, and that excludes the manager.... who is a decent manager, but I'm not certain he knows which end of the screwdriver to hang onto).

Back in the coach it goes.

Dolph

[George Beckman]

Mr ERFisher wrote on Sun, 18 November 2012 16:50

> since your are in Wash
>
> read this
> http://gmcmotorhome.info/engine.html#canister
>
> this is what I am going to do in Orgn.
>
> remove the line at the liquid separator
> and install a new one
> run the exit hose down so any vapor goes behind the wheels and away from
> the exhaust
>
>
> jwid
> gene

I respectfully disagree with this one. First, there _will_ be vapor. We hear all the time about ethanol "boiling". Second, it is not necessarily only happening when you are driving, Pumped gas is usually cooler than most days in GMC weather so there will be expansion. Third, between the wheels is also near the closet and bedroom. (my wife doesn't want to smell any gasoline... ever.) Fourth, the canister is good for the atmosphere and you get to use gas that does boil off.
--
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George

[gene Fisher]

>
> I respectfully disagree with this one. First, there _will_ be vapor.

Yes, good thing.
If It works, don't fix it (IIWDFI)

but
if you get pressure (plus or minus) when you remove the gas cap
- your vapor vent system is, broken, plugged, - not working-
- you have 3/4 in diameter, of vents on each tank, the tank should never
have pressure
- almost all of the rubber vapor vents, have leaking rubber lines already

so
you have pressure, you have:
- broken liquid separator
- crimped rubber lines
- rusted - plugged- metal crossover line
- broken canister (dripping goo out the bottom)
-

We hear all the time about ethanol "boiling".

so?

> Second, it is not necessarily only happening when you are driving,

Pumped gas is usually cooler than most days in GMC weather so there will be
expansion. Third, between the wheels is also near the closet and bedroom.
(my wife doesn't want to smell any gasoline... ever.)

so?

Fourth, the canister is good for the atmosphere and you get to use gas
that does boil off.

- unless
- they are dripping clear goo onto the ground
- blowing gas out the fill line
- placing an UN-acceptable leak on the engine vacuum system

Do what you will
but
know where your problems are,
- pressure in the tank is not normal

JWID
gene

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Carl Stouffer]

The question I have is: If it doesn't work, why not fix it right? The parts are all available and it's not a complicated system. It's just not that hard.
--
Carl S.
'75 ex Palm Beach
Tucson, AZ.

[Matt Colie]

I am going to interject my thoughts into this discussion at some peril, but there are points that need to be included.

>> George wrote:
>> I respectfully disagree with this one. First, there _will_ be vapor.

>Gene wrote:
>Yes, good thing.
>If It works, don't fix it (IIWDFI)

*** Corollary ***
If it isn't working, find the problem and fix it right - the first time.

>but
>if you get pressure (plus or minus) when you remove the gas cap
>- your vapor vent system is, broken, plugged, - not working-

*** See above

>- you have 3/4 in diameter, of vents on each tank, the tank should never have pressure

*** The fill vents (back to the neck are 3/8, the vapor vent is 5/16 from the tank.

>- almost all of the rubber vapor vents, have leaking rubber lines already

*** See above

>so
>you have pressure, you have:

>- broken liquid separator *** See above
>- crimped rubber lines *** See above
>- rusted - plugged- metal crossover line *** See above

>- broken canister (dripping goo out the bottom)

*** If the canister is ever dripping anything, then the vapor trap valve is toast. JimK has the replacement in stock.

>>We hear all the time about ethanol "boiling".
>so?

*** You'r kidding - Right?

>> Second, it is not necessarily only happening when you are driving,

>>Pumped gas is usually cooler than most days in GMC weather so there will be expansion. Third, between the wheels is also near the closet and bedroom. (my wife doesn't want to smell any gasoline... ever.)
>so?

*** If you have a wife, this is a big issue. (Unless you like traveling alone.)

>> Fourth, the canister is good for the atmosphere and you get to use gas that does boil off.

*** I bought it, I want to burn it not dump it.

>- unless
>- they are dripping clear goo onto the ground *** See above

>- blowing gas out the fill line

*** There's that replacement vapor valve again......

>- placing an UN-acceptable leak on the engine vacuum system

*** If the valve on the vapor canister is functional and the manifold porting is correct (like the manual calls out) then the vacuum leak is not "Un-acceptable".

>Do what you will
>but know where your problems are,
>- pressure in the tank is not normal

JWID
gene

*** Matt Here***
The coach fuel system was designed to run with less than 2"WC pressure/vacuum. This amounts to minor "Paah" when you open the cap. If you have more than that, find out why.

I run with very careful fuel management (a habit), and as a result we frequently put on 50+ (53.6 record) gallons of fuel at a stop. if we were to do that and then hold up for a hot night (but not so hot as to need the A/C and/or cook with the microwave - both will pull on the fuel tank), there might be fuel up to the vapor valve. So, some pressure could then build in the tank. Since that never happens and it only takes a few (unfortunately few) miles to make more vapor space in the fuel tanks, this has never been an issue.

If you are going to run with the system disabled, you would do well to change to a vented gas cap and put up with the fuel spitting up on the coach side. (Mine did and your will.) If you leave the vapor vent line open in the port wheel well, it will spill fuel if you try to press up the tanks and suck in bugs and road crud (bugs are a big problem in boat fuel tank vents - road crud, not so much). It is lower than the fill neck, so if the tanks are filled, it will spill liquid fuel on the ground if it is open.

This is all the results of my learning from experiments to date. All experiments are successful, if you don't get the result you expected, it just means you were wrong in your assumptions. The experiment did not fail.

"I have not failed 1,000 times. I have successfully discovered 1,000 ways to NOT make a light bulb." T.A. Edison

Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will find
SE Michigan - Twixt A2 and Detroit

[Dolph Santorine]

Yep.

Smart guys with slide rules designed this stuff

Deleting it is like doing away with the PCV system.

Dolph Santorine

Do...@DolphSantorine.com

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