Home » Public Forums » GMCnet » [GMCnet] Priming procedure after emptying gas tanks?
| [GMCnet] Priming procedure after emptying gas tanks? [message #347927] |
Mon, 16 September 2019 11:53  |
Gerard Hickey
Messages: 53
Registered: June 2019
Karma: 1
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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
hickey@kinetic-compute.com DMR: 3102272
425-395-4554
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #347930 is a reply to message #347927] |
Mon, 16 September 2019 12:52  |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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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
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #347939 is a reply to message #347927] |
Mon, 16 September 2019 14:55 |
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Tom Newell
Messages: 25
Registered: August 2017
Location: Los Angeles, California
Karma: 0
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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
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #347991 is a reply to message #347939] |
Mon, 16 September 2019 17:47 |
Gerard Hickey
Messages: 53
Registered: June 2019
Karma: 1
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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
hickey@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
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #347992 is a reply to message #347940] |
Tue, 17 September 2019 03:47 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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6cuda6 wrote on Mon, 16 September 2019 15:00If 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
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #347995 is a reply to message #347992] |
Tue, 17 September 2019 07:28 |
GMC.LES
Messages: 505
Registered: April 2014
Karma: -2
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Senior Member |
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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'
> On Sep 17, 2019, at 4:47 AM, Ken Burton via Gmclist wrote:
>
> 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
>
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #347998 is a reply to message #347927] |
Tue, 17 September 2019 09:10 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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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
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #348004 is a reply to message #347998] |
Tue, 17 September 2019 09:32 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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> On Sep 17, 2019, at 10:10 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.
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
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #348010 is a reply to message #347927] |
Tue, 17 September 2019 10:04 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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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
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #348042 is a reply to message #348036] |
Tue, 17 September 2019 15:49 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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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
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #348045 is a reply to message #348041] |
Tue, 17 September 2019 16:18 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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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
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #348146 is a reply to message #348111] |
Thu, 19 September 2019 20:08 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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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
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #348147 is a reply to message #348146] |
Thu, 19 September 2019 20:17 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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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 Mondor,
Brockville, ON
77 Hughes 2600
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #348160 is a reply to message #348147] |
Fri, 20 September 2019 07:36 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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6cuda6 wrote on Thu, 19 September 2019 21:17Now 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 - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Priming procedure after emptying gas tanks? [message #348173 is a reply to message #348160] |
Fri, 20 September 2019 10:14 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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Matt Colie wrote on Fri, 20 September 2019 08:366cuda6 wrote on Thu, 19 September 2019 21:17Now 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
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