[GMCnet] Priming procedure after emptying gas tanks?

[Gerard Hickey via Gmclist]

This past weekend, I dropped both gas tanks to replace a bunch of
cracked vent hoses. I also found the vent on the rear tank loose. It had
been repaired at some point in the past and the glue that was used was
now cracking and falling off. I repaired it with JB weld and it is now
nice and strong. Hoses replaced and everything put back together. I
tried to be pretty careful about making sure the hoses stayed in the
track and did not get pinched or crossed as the tanks got put back in place.

Poured 10 gallons of the 15 gallons of gas drained from the tanks back
into the tanks. But I could not get the engine to start back up again.
Turned it over for quite a while and drained the battery. It has been
charging overnight and I will try again late afternoon or this evening.

I can understand that it can take a good amount of effort to get the gas
back up to the engine given that the lines were emptied out and such.
But that got me thinking if there was a priming procedure when the tanks
have been emptied.

Any other thoughts of what I should do or could have missed?

Thanks.

--
Gerard Hickey / WTØF IRLP:3067/Echolink:529661
hic...@kinetic-compute.com DMR: 3102272
425-395-4554

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

[Carl Stouffer via Gmclist]

That's one situation where an electric pusher pump comes in handy, but in the absence of that I think it would be smart to use a small squirt bottle
to fill the carb fuel bowl through the bowl vent. That should get the coach running, then it should suck enough gas to the fuel pump to keep it
running. Be careful not to spill any gas on the engine because a backfire could ignite it, then things will get exciting (it might be prudent to have
a fire extinguisher handy).
--
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

[Tom Newell via Gmclist]

Hi Gerald,

In order of ease for pulling the fuel through the lines, these will work.

1. A Facet style inline fuel pump wired with alligator clips to attache to the battery. (Long wires, safety procedures, etc.; sparks and gasoline,
well you know). Versions of these pumps are available in different brands, etc. at every auto parts store (well, most every, I guess).

A representative example:
https://www.amazon.com/dp/B000BM6G6O/ref=psdc_15728151_t3_B000P4W2AW


2. A hand transfer pump. This is, I suppose, the easiest to set up, as they come with a conical adapter you can jam into a rubber hose. Takes more
physical effort of course.

Cheap, works fine:
https://www.harborfreight.com/multi-use-transfer-pump-63144.html


3. A hand vacuum pump with a brake bleeding reservoir. These work fine and are easy to set up; it is also quite easy to get carried away and suck the
gas into the pump itself.

A vacuum pump is a very useful tool (works as a vacuum gauge too), and this is quite a decent one for the money.
https://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-63391.html

Good Luck,

Tom Newell
San Pedro, California
--
Proud Citizen of
Los Angeles, California
Founded 1781 as
El Pueblo de la Reyna de los Angeles, Alta California

[tonka6cuda6--- via Gmclist]

If you have a compressor you can pressurize the tanks by sending air in from a blow gun via the fuel filler at the cap....just wrap a rag around the
blowgun and add air.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600

[Gerard Hickey via Gmclist]

I know that I have a hand transfer pump around somewhere, but it would
take a while to find it and the hoses. But I do have the hand vacuum
pump from bleeding the brakes on a car. So how or where would I hook it
up to use it? Do I want to put the vacuum pump up at the fuel line at
the engine?

--
Gerard Hickey / WTØF IRLP:3067/Echolink:529661
hic...@kinetic-compute.com DMR: 3102272
425-395-4554

On 9/16/19 12:55 PM, Tom Newell via Gmclist wrote:
> Hi Gerald,
>
> In order of ease for pulling the fuel through the lines, these will work.
>
> 1. A Facet style inline fuel pump wired with alligator clips to attache to the battery. (Long wires, safety procedures, etc.; sparks and gasoline,
> well you know). Versions of these pumps are available in different brands, etc. at every auto parts store (well, most every, I guess).
>
> A representative example:
> https://www.amazon.com/dp/B000BM6G6O/ref=psdc_15728151_t3_B000P4W2AW
>
>
> 2. A hand transfer pump. This is, I suppose, the easiest to set up, as they come with a conical adapter you can jam into a rubber hose. Takes more
> physical effort of course.
>
> Cheap, works fine:
> https://www.harborfreight.com/multi-use-transfer-pump-63144.html
>
>
> 3. A hand vacuum pump with a brake bleeding reservoir. These work fine and are easy to set up; it is also quite easy to get carried away and suck the
> gas into the pump itself.
>
> A vacuum pump is a very useful tool (works as a vacuum gauge too), and this is quite a decent one for the money.
> https://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-63391.html
>
> Good Luck,
>
> Tom Newell
> San Pedro, California

_______________________________________________

[Ken Burton via Gmclist]

6cuda6 wrote on Mon, 16 September 2019 15:00

> If you have a compressor you can pressurize the tanks by sending air in from a blow gun via the fuel filler at the cap....just wrap a rag around
> the blowgun and add air.

I have done this method many times. Just do not get carried away with this. 5 seconds of shop air is probably enough, 10 seconds max if the shop rag
is fairly tight. You are only trying to raise the fuel in the line up from the level in the tanks about maybe 8"-10" total.

If that does not work you probably have a hose not connected or a leak somewhere. If there is a leak the pressure you previously applied will cause
the hose to leak gasoline and you will be able to easily see the leak.

I am doing the same job except on the coach I am working everything is rusted. The coach sat for 19 years with 1/2 full tanks. Two of us spent about
16 hours just to get them down this weekend. Had to use a 1/2" impact and lots of kroil everywhere just to get the 6 bolts on the front of the tanks
loose. Lots of in and out - in and out on the bolts, with oil applied each time to get them out. Broke two of the vertical hanger bolts in the
process. Got a couple of new bolts today that I will cut the heads off and bend the ends with a flame wrench to make new ones.

Surprisingly the tank insides and sending units are beautiful. The outside of the tank is badly rusted but no leaks. I haven't decided how I am
going to strip the rust and what I will use to clean them. I also haven't what to use to coat the outside again. Cold galvanize? Maybe POR-15 with
white Rustoleum top coat.

I would also like to flush them but have not to decided how to do that.

Anyway, try a little shop air. It is quick and it does not take much air.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Les Burt via Gmclist]

Someone posted here a while back that they tried pressurizing their fuel tanks with shop air to look for leaks, and found that they balloon quite easily. BE CAREFUL if trying this. Due to the large surface area of these tanks, it takes very few PSI to swell or bulge them.

Les Burt
Montreal
'75 Eleganza 26'

[Jon Roche via Gmclist]

the couple times I have done he gas tanks on coaches. it always took 15 gallons to get it to start. so I would pour a 3rd 5 gallon gas can in the
tank, and I bet it will pump the fuel and fire off.

I have always installed an electric pump on the aux side when I have done tanks, so that helped prime, but seems to take 15 gallons for some odd
reason.
--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/

[Jim Miller via Gmclist]

> On Sep 17, 2019, at 10:10 AM, Jon Roche via Gmclist <gmc...@list.gmcnet.org> wrote:
>
> the couple times I have done he gas tanks on coaches. it always took 15 gallons to get it to start. so I would pour a 3rd 5 gallon gas can in the tank, and I bet it will pump the fuel and fire off.

Due to the common tank filling tube arrangement most of the gas that goes into the fill tube is carried by inertia to the rear (aka “main”) tank and the front tank doesn’t get an equal amount. My guess is that with 15 gallons poured in you might get 12 gal in the rear and 3 in the front. The tanks will only equalize their level via the common fill tube once one of them reaches about 2/3 full.

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH

[Johnny Bridges via Gmclist]

Quick n dirty (if you're a country boy like me) remove the line from the front frame crossover. First blow into it. If it bubbles, there's gas at
the other end. If it doesn't bubble, there isn't any gas at the pickup, add some. Then, siphon the line until you feel pressure instead of suction,
and put the end on the ground. Once gas come out cover the end with your thumb, slide it back on the pipe, and it ought to fire up quickly. To speed
it up, throw a small amount of gas down the carb throat, REPLACE THE AIR CLEANER, and when it fires it should pump fairly well.

--johnny

--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Gerard Hickey via Gmclist]

Well I visited the motorhome yesterday evening to try a few things. I
brought along the hand vacuum pump that I have from Harbor Freight for
bleeding breaks based on the email from Tom Newell. I found the line
that was coming up from the vapor canister (at least I think that is
what it was mounted behind the passenger front tire). I was a little
horrified to find that the hose was just pushed on (engine side) with no
hose clamp and the hose is cracking a bit at the engine. So yet another
hose to replace--at least this is an easy one to do.

I pumped for several minutes and could never get any vacuum to form. I
also sucked on the line a bit and could taste just a bit of vapor.
Plugged the hose back in and the engine started after a turn over or
two. Let it run for a couple of mins and it stalled eventually. I figure
it just was not getting enough fuel. I also did not try to switch tanks
and see if it would keep running.

I can believe that 15 gallons is a good amount to have in the tank and
get the gas line primed. Seems that with the 10 gallons I have in there
now is just enough.

Thanks for everybody's help and thoughts.

--
Gerard Hickey / WTØF IRLP:3067/Echolink:529661
hic...@kinetic-compute.com DMR: 3102272
425-395-4554

On 9/17/19 7:10 AM, Jon Roche via Gmclist wrote:
> the couple times I have done he gas tanks on coaches. it always took 15 gallons to get it to start. so I would pour a 3rd 5 gallon gas can in the
> tank, and I bet it will pump the fuel and fire off.
>
> I have always installed an electric pump on the aux side when I have done tanks, so that helped prime, but seems to take 15 gallons for some odd
> reason.

_______________________________________________

[Tom Lins via Gmclist]

Les Burt[1
> wrote on Tue, 17 September 2019 08:28]Someone posted here a while back that they tried pressurizing their fuel tanks with shop air to look for

> leaks, and found that they balloon quite easily. BE CAREFUL if trying this. Due to the large surface area of these tanks, it takes very few PSI to
> swell or bulge them.
>
> Les Burt
> Montreal
> '75 Eleganza 26'

I have to agree about ballooning the tanks.
I for a few years I collected used vegetable oil from restaurants to make biodiesel.
We lived in New Jersey so in the winter the oil would get very thick and there was a time or two
we nearly exploded the 55 gal drums getting the oil out of the drums.
That was with less than 15 pounds of pressure. Even 10 pounds is iffy.


--
Tom Lins
St Augustine, FL
77 GM Rear Twin, Dry Bath, 455, FI-Tech EFI, Aluminum Radiator Quad-Bag Suspension Solar Panel
Manuals on DVD
GMC Dealer Training Tapes
http://www.bdub.net/tomlins/

[Ken Burton via Gmclist]

I cannot figure out what good it would do to try to suck on a vent line. It would be counter productive.

I do not see how you could get much vacuum up with 35 gallons air in the empty parts of the tanks. You also are being counter productive in that you
want the gas to flow towards the engine not away from it which a vacuum would cause.

If you insist on using a vacuum, disconnect the rubber line to the to the input of the pump and suck there. There you are only sucking on the line
and not whole tank.

The problem you will have doing it this way is once you get gas to flow, you will loose most of it when you disconnect the vacuum pump and reconnect
the line to the fuel pump. During that time all, or most, of the gas will run backwards to the tank again.

A little bit of air applied to the fuel filler is so much easier. If you do not have air available, a small portable air tank will do the job. If
you have two people, have one crank while the other applies air in 5 second bursts. 5 sec on and 5 sec off. Usually one or two bursts is all you
need. One person can also do it alone. Give it 5 seconds, then go inside and crank. Repeat if necessary if it does not start.

You are just trying to assist mechanical pump to initially move the gas up the line to the pump.

Good Luck

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Ken Burton via Gmclist]

The difference here is we are only trying to move gas from the tank level to the input side of the gas pump. Gasoline weighs 6 pounds per gallon and
we are only moving few ounces mostly horizontal with a few inches of lift. I and others have done this many, many times.

You can move that quantity and lift with lung pressure. Have you ever siphoned gas starting it by mouth? You were lifting more gas higher then than
what is needed to get gas to flow to this pump. Also do not forget that there is a pressure relief through carbon canisters. I and others have done
this many many times. I learned this from an older than me GMCer one time when we went to retrieve a GMC out of a junk yard in New York.

If my calculations are correct you will need .32 PSI to raise it 12 inches from tank to pump. You are not going to balloon a tank at that pressure or
even 10 times that pressure.

If you are afraid of it, DO NOT DO IT.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[tonka6cuda6--- via Gmclist]

Guys like i said and Ken has said....if done correctly you will not hurt anything....i have done this literally hundreds of times over my career so
far.

The problem here is the fuel pump must suck fuel from the tanks and the tanks are a long way away from it....if you have worked with fuel systems
you'll know this is one if not the most ineffeciant ways of doing things plus it doesnt suck air to well so we have to get the fuel to it first then
keep it there with check valves.

--
Rich Mondor,

Brockville, ON

77 Hughes 2600

[tonka6cuda6--- via Gmclist]

Now if you dont have a compressor you can use an air pig (portable tank)....if you dont have that you can make something using a cheap gas cap, rad
cap, plastic cap, pretty much anything that will go onto the filler neck, put a tire valve or schradder valve in it and grab a bicycle
pump.......never tried bicycle pump and rags jammed in filler though but my gut tells me that it wont seal enough with the rags i think.

[Matt Colie via Gmclist]

6cuda6 wrote on Thu, 19 September 2019 21:17

> Now if you dont have a compressor you can use an air pig (portable tank)....if you dont have that you can make something using a cheap gas cap,
> rad cap, plastic cap, pretty much anything that will go onto the filler neck, put a tire valve or schradder valve in it and grab a bicycle
> pump.......never tried bicycle pump and rags jammed in filler though but my gut tells me that it wont seal enough with the rags i think.

Rich,

If you are going to put pressure in GMC tanks, you had best be careful. Several of the too many times I had my tanks down, I tried to use air to
check for leaks in the work I had just done. I never did any damage, but I also know that the pressure I used was less than two feet of water (less
than 1 psi). Even with that, the tanks were notably inflated and distorted.

The stock fuel cap is supposed to limit pressure at less than 1 PSI.

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

[tonka6cuda6--- via Gmclist]

Matt Colie wrote on Fri, 20 September 2019 08:36

> 6cuda6 wrote on Thu, 19 September 2019 21:17
> > Now if you dont have a compressor you can use an air pig (portable tank)....if you dont have that you can make something using a cheap gas
> > cap, rad cap, plastic cap, pretty much anything that will go onto the filler neck, put a tire valve or schradder valve in it and grab a bicycle
> > pump.......never tried bicycle pump and rags jammed in filler though but my gut tells me that it wont seal enough with the rags i think.
>
> Rich,
>
> If you are going to put pressure in GMC tanks, you had best be careful. Several of the too many times I had my tanks down, I tried to use air to
> check for leaks in the work I had just done. I never did any damage, but I also know that the pressure I used was less than two feet of water (less
> than 1 psi). Even with that, the tanks were notably inflated and distorted.
>
> The stock fuel cap is supposed to limit pressure at less than 1 PSI.
>
> Matt

Sure one can over do it.....but the fuel will move first then we will start to pressurize. I like to use a rag that way the air is control....a cap
and a bicycle pump will not build enough pressure to damage the tanks as you would have to pump for a LONG time.....now if the tanks were full perhaps
but almost empty.....

--
Rich Mondor,

Brockville, ON

77 Hughes 2600