Cleaning gas tanks

K

kmorefield

Member
Jan 4, 2020
62
6
8
Hi all,
I have dropped both fuel tanks, in order to replace lines, rehab sending units, possible in-tank fuel pumps, etc. The tanks each had about 10 gallons
of gas in them, which didn't seem overly bad (the gas). I've drained the tanks, and they don't seem to bad inside (a little bit of rust right at the
large fuel intake, where gas enters the tank when filling). But very minimal. There does seem to be a little bit of debris inside (minimal). What is
the best way to clean these tanks out, and try to remove all little floating/sinking particles? I thought I would powerwash the outside of the tank,
to get off the dirt and grime. I've read online where people will fill the inside of the tank full of water, flushing it multiple times. Then dry it
out over a few days, and maybe spray air inside to help dry and maybe blow out remaining particles. Is this how it is normally done? I don't think
they're dirty enough to have a radiator or fuel tank show clean them for $$$. But I certainly don't want to screw them up... Any advice?
--
1975 - 26’ Eleganza II
Unsure of what upgrades may have been done. I'm working on sorting that out in the coming months.
Ken Morefield - Redding, CA
 
Install an in line filter and let it do the work.

Sully
Bellevue wa

On Tue, May 5, 2020 at 3:34 PM Ken Morefield via Gmclist <

> Hi all,
> I have dropped both fuel tanks, in order to replace lines, rehab sending
> units, possible in-tank fuel pumps, etc. The tanks each had about 10 gallons
> of gas in them, which didn't seem overly bad (the gas). I've drained the
> tanks, and they don't seem to bad inside (a little bit of rust right at the
> large fuel intake, where gas enters the tank when filling). But very
> minimal. There does seem to be a little bit of debris inside (minimal).
> What is
> the best way to clean these tanks out, and try to remove all little
> floating/sinking particles? I thought I would powerwash the outside of the
> tank,
> to get off the dirt and grime. I've read online where people will fill the
> inside of the tank full of water, flushing it multiple times. Then dry it
> out over a few days, and maybe spray air inside to help dry and maybe blow
> out remaining particles. Is this how it is normally done? I don't think
> they're dirty enough to have a radiator or fuel tank show clean them for
> $$$. But I certainly don't want to screw them up... Any advice?
> --
> 1975 - 26’ Eleganza II
> Unsure of what upgrades may have been done. I'm working on sorting that
> out in the coming months.
> Ken Morefield - Redding, CA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
One of the biggest incorrect assumptions there is, is that once you clean
your tanks that your dirt problems are over. Our fuel supply, be it
pipeline or semi-truck and trailer, has crud in it. Some, worse than
others. So, you need to do like Todd says, filter your fuel, preferably
before the gas in the tank reaches the pump. Pretty hard to do with in-tank
pumps. Just my take on it.
Jim Hupy
Salem, Oregon

On Tue, May 5, 2020, 4:44 PM Todd Sullivan via Gmclist <

> Install an in line filter and let it do the work.
>
> Sully
> Bellevue wa
>
> On Tue, May 5, 2020 at 3:34 PM Ken Morefield via Gmclist <

>
> > Hi all,
> > I have dropped both fuel tanks, in order to replace lines, rehab sending
> > units, possible in-tank fuel pumps, etc. The tanks each had about 10
> gallons
> > of gas in them, which didn't seem overly bad (the gas). I've drained the
> > tanks, and they don't seem to bad inside (a little bit of rust right at
> the
> > large fuel intake, where gas enters the tank when filling). But very
> > minimal. There does seem to be a little bit of debris inside (minimal).
> > What is
> > the best way to clean these tanks out, and try to remove all little
> > floating/sinking particles? I thought I would powerwash the outside of
> the
> > tank,
> > to get off the dirt and grime. I've read online where people will fill
> the
> > inside of the tank full of water, flushing it multiple times. Then dry it
> > out over a few days, and maybe spray air inside to help dry and maybe
> blow
> > out remaining particles. Is this how it is normally done? I don't think
> > they're dirty enough to have a radiator or fuel tank show clean them for
> > $$$. But I certainly don't want to screw them up... Any advice?
> > --
> > 1975 - 26’ Eleganza II
> > Unsure of what upgrades may have been done. I'm working on sorting that
> > out in the coming months.
> > Ken Morefield - Redding, CA
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
You could wash them out with water and Dawn (or something like it), but like Todd suggests, install an inline filter and let it catch the little
particles (if they get past the socks). Mine were pretty much spotless inside due to the ethanol gas that had been run in them for several ears.
Putting a fan in the sender hole and leaving the tanks in the sun, should dry them out well.

I cleaned the outsides of mine with Simple Green and a Scotch Brite sponge and then painted them
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
When the fuel level drops in the tank, air displaces the fuel. That air is
not filtered, but dirty and dusty air from traffic. Also the way our tanks
are constructed, you will not achieve total clean tank.

On Tue, May 5, 2020 at 5:09 PM Carl Stouffer via Gmclist <

> You could wash them out with water and Dawn (or something like it), but
> like Todd suggests, install an inline filter and let it catch the little
> particles (if they get past the socks). Mine were pretty much spotless
> inside due to the ethanol gas that had been run in them for several ears.
> Putting a fan in the sender hole and leaving the tanks in the sun, should
> dry them out well.
>
> I cleaned the outsides of mine with Simple Green and a Scotch Brite sponge
> and then painted them
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
So a filter on the vent air would be good.

Chaplain Randy Hecht
Roswell, GA
Chaplains are ready to Listen when you're ready to talk.

1974 Canyon Lakes GMC the Unicorn Express
80mm Front Disc and a work in progress

>
> When the fuel level drops in the tank, air displaces the fuel. That air is
> not filtered, but dirty and dusty air from traffic. Also the way our tanks
> are constructed, you will not achieve total clean tank.
>
>> On Tue, May 5, 2020 at 5:09 PM Carl Stouffer via Gmclist <

>>
>> You could wash them out with water and Dawn (or something like it), but
>> like Todd suggests, install an inline filter and let it catch the little
>> particles (if they get past the socks). Mine were pretty much spotless
>> inside due to the ethanol gas that had been run in them for several ears.
>> Putting a fan in the sender hole and leaving the tanks in the sun, should
>> dry them out well.
>>
>> I cleaned the outsides of mine with Simple Green and a Scotch Brite sponge
>> and then painted them
>> --
>> Carl Stouffer
>> '75 ex Palm Beach
>> Tucson, AZ.
>> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
>> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
>> Eagles,
>> Solar battery charging. GMCSJ and GMCMI member
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk
> http://www.gmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
> When the fuel level drops in the tank, air displaces the fuel. That air is
> not filtered, but dirty and dusty air from traffic. Also the way our tanks
> are constructed, you will not achieve total clean tank.

Jim,

Isn't the air that goes back into the tanks filtered through the charcoal canister filter? I wouldn't think much dirt would be introduced into the
tanks that way.

--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
Carl
Not Jim here but I don’t think any air to the tanks goes through the charcoal canisters. The carburetor (or tbi system) puts a vacuum on the canisters and pulls air through them to recover the fuel vapors that flow from the fuel tanks. No air flows to the tanks. The fuel cap is vented so air flows through it.

Emery Stora
77 Kingsley
Frederick, CO

>

>> When the fuel level drops in the tank, air displaces the fuel. That air is
>> not filtered, but dirty and dusty air from traffic. Also the way our tanks
>> are constructed, you will not achieve total clean tank.
>
> Jim,
>
> Isn't the air that goes back into the tanks filtered through the charcoal canister filter? I wouldn't think much dirt would be introduced into the
> tanks that way.
>
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
I do not think any air goes back inside the tanks to fill the space of used gasoline. If it did, you would have an explosive mix of air and gasoline
vapor in the tank waiting for an ingition source. I believe what fills the empty space in the tank is gasoline vapor that is some of the liquiid
gasoline that has expanded (evaporated) into a gaseous vapor.

On a modern vehicle we have an air tight system that is checked for leaks by the BCM, or ECM, or PCM on every cold start.

If it was air, we would stand the chance of it exploding with the ignition source being the in tank pump or fuel sending unit.

We do not have a vented cap on our coaches. At least the one on mine is not vented.

But what do I know?
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Everybody ready?
Here he goes again.
Most of us here have some history, but how many of you were running a small boat and it stopped because nobody unscrewed the little vent thing??
OK? So much for that case.

If there were no means to backfill the fuel tanks with air (that being the only inexpensive thing that is universally available), what would the
pressure in the tanks and the piece of fuel line just south of the engine driven fuel pump become? (Hint, in the early days of scientific
investigation, the only practical way to produce a vacuum was to pump the water out of a sealed vessel.) Without this, you could see vapor lock on a
winter day.

More automotive history.
Remember the late 60s and early 70s and the filler cap hidden behind the license plate? If they had a vented cap, every hole shot would have produced
a wet fuel trail. (Actually, when the tank was full and the owner had replaced the cap, they often did.) This was also the time of the introduction
of the carbon canister in the brand new evaporative emissions system. From that point on, most every thing has had a "Non-Vented" cap on the fuel
system. But, even the non-vented caps are supposed to have a relief pressure (in the nature of 1 psi) to prevent the situation where a gush of fuel
soaks the citizen when the cap is removed. (This is also the reason why the newer caps got a deep shoulder to redirect the exiting fuel and/or
vapors.)

Now, let's consider the TZE fuel system for a moment. Some of us are very familiar with this. If there were no means to backfill the tanks with air,
and with all the surface area of those tanks, it would not take much negative pressure to turn them into giant raisins. By the same token, if you
ever pressure tested your tanks that were sitting on your barn floor and you let the pressure in the tank get much north of a single pound, you would
have seen that tank (assuming you had actually fixed that leak at the vent fitting) try to be come a large steel balloon.

We have to go back and look at the carbon canister again now. It isn't just a can with two nipples. There is usually a funny little hat on there
that contains a some valves. Because of the newer fuel vapor rules these did get to be more simple in recent years. Of course, for most tank volumes,
those couldn't just be simple check valves. That would be too easy. They are a set of valves and one set allows air back into the fuel tanks as
discussed above. But, if the volume of vapor coming out of the tanks gets too high for the carbon to manage, that it will direct that vapor to the
purge system so it can hopefully fill the engine intake system and not be so noticeable. (A small TZE aside here. When your vent valve went bad and
you ended up with wet fuel on the ground under the passenger seat, this wet the carbon down and now every time you returned to the coach after a hot
stop, the presence of O'Esso is waiting. It will go away when the carbon canister has had enough purge time. That can take a while and once the
carbon has been wetted, it take a lot longer to purge after that. Replacement carbon elements and can bottom filters are available.

And, just one more little note for the Kens here. B brought it up but I bet H will understand too...
There is an actual SAE standard relating to fuel level sending units. They are just about all a wire wound pot connected to the float. The standard
says that the maximum potential between wires at the wiper can be no more than 30mV. This is exactly to prevent arcing inside the tank.

OK, I'm done for now. But if I have missed something or left a question.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
> Carl
> Not Jim here but I don’t think any air to the tanks goes through the charcoal canisters. The carburetor (or tbi system) puts a vacuum on the
> canisters and pulls air through them to recover the fuel vapors that flow from the fuel tanks. No air flows to the tanks. The fuel cap is vented so
> air flows through it.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>

> >

> >> When the fuel level drops in the tank, air displaces the fuel. That air is
> >> not filtered, but dirty and dusty air from traffic. Also the way our tanks
> >> are constructed, you will not achieve total clean tank.
> >
> > Jim,
> >
> > Isn't the air that goes back into the tanks filtered through the charcoal canister filter? I wouldn't think much dirt would be introduced
> > into the
> > tanks that way.
> >
> > --
> > Carl Stouffer
> > '75 ex Palm Beach
> > Tucson, AZ.
> > Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear
> > American Eagles,
> > Solar battery charging. GMCSJ and GMCMI member
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Emery,

Yes, I understand that the carburetor puts a vacuum on the charcoal canister when the engine is running, but isn't there a possibility that the tanks
might have a vacuum on them and then suck air back through that system after engine shut down or tank cool down?

It seems to me that the vent system would work both ways under different circumstances.

--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
Thanks Matt. I suspected that there might be the possibility of reverse air flow through the carbon canister and back to the tank(s) on out tanks.
That is probably why there are air filters on the bottom? of those canisters. I have never had one apart.

On modern Evap systems the carbon canister is open to the outside air and there is an electric valve on that vent opening to close it off for testing.
The BCM applies a vacuum (I believe using the purge valve) and then reads the pressure, or lack there of, at the tank. That is how they check that
everything is tight (No leaks) with the whole system including the gas cap.

Thanks for the education Matt.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
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