Fuel Leakage

[phil swanson]

Hello Fellow GMCers,

A couple of weeks ago, I pulled my 23' 73 Canyon Lands into a gas
station and filled it for the first time since I bought it about 8 weeks
ago. To my surprise, as it neared the full point, gas started flowing
all over the ground. At first I didn't see it, the attendant came
running up to me yelling that I was spilling gas all over the place. I
started it anyway and moved it out of the way and left it parked while I
did some other shopping at our local Costco here in the San Diego area
(Bonita). I just wondered if anyone else has had this problem. I figure
that the rubber fuel line connectors are shot because once it leaked a
couple of gallons, it stopped and all appeared okay. I figure that age
just got to the rubber hoses between the filler neck and the tank.
Anyone else had this problem? And if so, was it a major job to change
the rubber connectors. I have the maintenance manual but it's hard to
tell from the pictures. Any information would be appreciated. It seems
like a corrective action here could also save a coach or two from going
up in fire too. I hope I don't have to drop those two big tanks.

Thanks (I won't say in
advance, that's a worn out phrase) , Phil

 

[chuck blanford]

Phil

I had the same problem with my 77 Kingsley. I dropped both fuel tanks and
replaced all fuel lines. Their was a loose hose on the rear tank; the
clamp was actually laying on top of the tank. When filled or parked on an
incline, the fuel would flow from this open vent fitting until the level
dropped. Very disconcerting at the service station. The tanks are not
that difficult to drop. I raised the entire coach and then lowered the
tanks onto my "creeper", rolled them out to clean up, replaced all fuel
lines from the tanks to the fuel pump, and now fuel up with peace of mind!

Chuck

- ----------
> From: Phil Swanson
> To: gmcmotorhome
> Subject: GMC: Fuel Leakage
> Date: Tuesday, February 24, 1998 9:25 PM
>
> Hello Fellow GMCers,
>
> A couple of weeks ago, I pulled my 23' 73 Canyon Lands into a gas
> station and filled it for the first time since I bought it about 8 weeks
> ago. To my surprise, as it neared the full point, gas started flowing
> all over the ground. At first I didn't see it, the attendant came
> running up to me yelling that I was spilling gas all over the place. I
> started it anyway and moved it out of the way and left it parked while I
> did some other shopping at our local Costco here in the San Diego area
> (Bonita). I just wondered if anyone else has had this problem. I figure
> that the rubber fuel line connectors are shot because once it leaked a
> couple of gallons, it stopped and all appeared okay. I figure that age
> just got to the rubber hoses between the filler neck and the tank.
> Anyone else had this problem? And if so, was it a major job to change
> the rubber connectors. I have the maintenance manual but it's hard to
> tell from the pictures. Any information would be appreciated. It seems
> like a corrective action here could also save a coach or two from going
> up in fire too. I hope I don't have to drop those two big tanks.
>
> Thanks (I won't say in
> advance, that's a worn out phrase) , Phil
>

 

[zachary zehnacker]

On our GMC, it turned out to be the fitting where the vent lines go in at
the top of the tanks. The fitting is angled up a little and apparently
hits the plywood floor when the tank is installed. Ours was broken on the
rear tank so that the fitting was very loose in the tank and allowed gas to
leak out. Once the tank got completely filled, gas would leak out of this
fitting at the top of the tank. Unfortunately, there is no way to check or
fix this without dropping the tank unless you try filling the tank and
seeing if it is leaking from the top. Ours did this for several years and
we never had any problems with it. The leak also told us when our tanks
were full . We have just fixed the fitting this winter by soldering it
back in (be careful with the gas vapors if you attempt this). We have not
yet filled the tanks to try it out, but we are pretty sure this will fix
our problem.
We have also made an indentation on the floor with a router so that the
fitting does not have any more clearance problems.

Zachary Zehnacker

 

[mike finnicum]

I had what sound like the same problem. At least the previous owner warned
me about it and said to fill it real slow at the end. He claimed it was a
flaw in GMC's design!

NO SO!

It was a simple fix using about $4 worth of hose. My gas overflow hose was
cracked (with age).

It's easy to get at if you remove the drivers side inner wheel skirt. Remove
about 6 screws/bolts from around the fender and one top inside the skirt.
Wiggle the inner skirt and she comes right out. The overflow tube is visible
and runs up the side of the gas filler tube. Replace it.

All told about a 1 hour job (that's with 30 minutes running to the parts
store).

There is also a rubber elbow at the bottom of the fuel filler tube. Mine was
fine, I did tighten the clamps. Since your leak quit after a couple of
minutes, it is probably fine. If it leaks, it leaks till you are empty.

Hope your problem is as easy as mine.

Mike Finnicum
78 GMC Eleganza
Naples, FL

 

[scott woodworth]

> On our GMC, it turned out to be the fitting where the vent lines go
in at the top of the tanks. The fitting is angled up a little and
apparently hits the plywood floor when the tank is installed.

Zachary,

From reading the part in your letter about how you had to router an
area out for clearance leads me to suspect that your body to frame
insulator strips are missing. These insulator strips act as body mounts
to hold the middle section of the coach body up off the frame. Many
times, these strips shrivel and fall out over the years leaving the body
unsupported in this area. If your body mounts have failed, the symptoms
may include: Air cleaner lid rubbing the underside of the engine cover,
air lines being pinched and other things of that nature. Take a look at
these areas and look for the air line in the rear that runs between the
frame and floor and you'll see what I mean.

- -Scott Woodworth

 

[zachary zehnacker]

> From reading the part in your letter about how you had to router an
>area out for clearance leads me to suspect that your body to frame
>insulator strips are missing. These insulator strips act as body mounts
>to hold the middle section of the coach body up off the frame. Many
>times, these strips shrivel and fall out over the years leaving the body
>unsupported in this area. If your body mounts have failed, the symptoms
>may include: Air cleaner lid rubbing the underside of the engine cover,
>air lines being pinched and other things of that nature. Take a look at
>these areas and look for the air line in the rear that runs between the
>frame and floor and you'll see what I mean.
>
>-Scott Woodworth

Scott,
Thanks for your suggestion. Our rubber is fine. Both pieces on the cross
member that the air lines travel along are in place and in good shape as
are the strips that travel the lengths of the frame rails. GM actually did
run our air lines pretty poorly. The lines to the drivers side were
squished between the rubber and plywood where they come out to the wheel
well. They were not in the open spot they are intended to be run in. We
never had a problem with them though which is really surprising (lucky?).
The tanks have a bump in them for one of the breathers (the other goes
into the same spot as the fuel supply line and is fine). This bump is
higher than the rest of the tank. Even though the breather comes out from
the side of the bump, it is at a slight upward angle and puts the hose and
hose clamp at risk of hitting the plywood. I believe that Wes at Cinnabar
reported a similar problem a while back so I don't think our problem is
unique.

Zachary Zehnacker

 

[bob drewes]

Dave; On Wed, 25 Feb 1998 15:55:37 EST you wrote the following

>The over flow vent is back by the rear bogies and sometimes an air pocket
will >force some fuel out there.
>Another place to see fuel dumped on a full tank is at the carbon canister
>just behind the right front wheel.
> had leaks at the top of each tank where the baffles are welded.

The small plastic unit located in the left rear wheel well will have two
rubber vent hoses attached to it. It is a vapor-liquid fuel separator, and
should not leak liquid fuel. The purpose of this unit is to allow the tanks
to vent vapors to the carbon canister that is located behind the right
front wheel. The vapors are collected by the carbon canister, and these
vapors are transmitted to a port on the carburetor with a rubber vent hose,
and the vapors are burned whenever the engine is running.

There is a floating ball in the vapor-liquid fuel separator, and whenever
the tanks are full enough, some liquid fuel will travel in the vapor hose
from the tank to the vapor-liquid fuel unit. When liquid fuel comes in
contact with the floating ball, the ball will float upwards in the liquid
fuel and close off the opening so as no liquid fuel will travel to the
carbon canister. If you have liquid fuel running out of the carbon
canister, chances are the float is stuck in the vapor-liquid fuel
separator. By removing this unit and shaking it, one can hear the ball
rattle in the unit if it is OK. If the ball is stuck, spraying inside the
unit with carburetor cleaner will usually free the stuck ball. Examine the
unit, as some have known to have split open and will leak liquid fuel.

There are six spot welds on each tank that hold the baffles in position in
the tank. There are three spot welds on each side of the center sending
unit, nine inches from the center of the sending unit. When the fuel tanks
are dropped down for repair or hose replacement, clean these spot welds off
and put on a dab of Permatex Fuel tank epoxy on each spot weld. This is
good insurance for further leaks in this area.

When the fuel tanks are dropped down, be sure to replace the large "O" ring
in the center sending unit assembly. These have been known to be leakers,
as my original "O" ring was incorrectly installed at the factory.

Bob