How can a fuel pump be in a tank?

[crimsonride]

Just wondering. Why doesn't it all blow up?

 

[95jeepgrndchke]

Just wondering. Why doesn't it all blow up?

Im not sure but I know its one of those wierd Chevy concepts! And a PITA if you ask me, pulling the whole tank just to get to the fuel pump.

 

[crimsonride]

Well, I've just installed a internal pump from a newer XJ into my 84, I had to mount the pump to my old sending unit and I'm not too confident with my electrical-fuel-pump-in-tank-installing skills. So why doesn't something spark and go boom?

 

[95jeepgrndchke]

Well, I've just installed a internal pump from a newer XJ into my 84, I had to mount the pump to my old sending unit and I'm not too confident with my electrical-fuel-pump-in-tank-installing skills. So why doesn't something spark and go boom?

I dont know I would like to hear more about this too, But until we figure it out if it does go BOOM! get some good pics!

 

[spencurai]

Magic!!!

 

[harkinoff]

Magic!!!

chevs are not the only ones that do this...My Ford Motorhome has this BS setup also, what a mother to get the tank out. luckily my buddies shop had a forklift, oh and back to the explosion thing, its called a ground wire and plastic

 

[95jeepgrndchke]

chevs are not the only ones that do this...My Ford Motorhome has this BS setup also, what a mother to get the tank out. luckily my buddies shop had a forklift, oh and back to the explosion thing, its called a ground wire and plastic

Yeah i know alot of Manufacturers do it now, I was stuck in the Sans Flats camp ground pulling one out of a 87' Chev and dumping gas into a cooler this past august! It was big PITA

 

[pokeyYJ]

Yeah i know alot of Manufacturers do it now, I was stuck in the Sans Flats camp ground pulling one out of a 87' Chev and dumping gas into a cooler this past august! It was big PITA

Thats why you cut a hole in the floor and pull the pump and sending unit out the top.

Also one reason for running an in-tank pump is to minimize parts, by sticking the pump inside the tank you don't need to run a return line for the FI, the pump just pumps right back into the tank when the pressure is reached.

 

[crimsonride]

I'd get some pics but it's already in my tank. I don't have to drop my tank, just climb under there and fiddle with the stupid lock ring. I don't have a very good grasp on electrical stuff I guess. I've got it grounded and I've got the tank grounded. For some reason it seems risky to put electrical crap in a tank full of gasoline fumes......whatever.

 

[spiderman]

Thats why you cut a hole in the floor and pull the pump and sending unit out the top.

Also one reason for running an in-tank pump is to minimize parts, by sticking the pump inside the tank you don't need to run a return line for the FI, the pump just pumps right back into the tank when the pressure is reached.

Not necessarily. A lot of internal fuel pump systems still run a return line. They use a pressure regulator to hold the pressure at the fuel rail, then the regulator sends the extra fuel back to the tank.

 

[pokeyYJ]

Not necessarily. A lot of internal fuel pump systems still run a return line. They use a pressure regulator to hold the pressure at the fuel rail, then the regulator sends the extra fuel back to the tank.

Yeah, I was thinking Chrysler cars

 

[jamesgeologist]

Gas and most other combustable materials need oxygen to burn. The atmosphere inside the tank must have a certain percentage of oxygen before anything will burn.

"Above the upper flammable limit (UFL) the mixture of substance and air is too rich in fuel (deficient in oxygen) to burn. This is sometimes called the upper explosive limit (UEL)."

"Below the lower flammable limit (LFL) the mixture of substance and air lacks sufficient fuel (substance) to burn. This is sometimes called the lower explosive limit (LEL)."

Hence; "Any concentration between these limits can ignite or explode -- use extreme caution! Being above the upper limit is not particularly safe, either. If a confined space is above the upper flammable limit and is then ventilated or opened to an air source, the vapor will be diluted and the concentration can drop into the flammable limit range."

"The lower flammable limit or lower explosive limit (LFL or LEL) of gasoline is 1.4 percent; the upper flammable limit or upper explosive limit (UFL or UEL) is 7.6 percent. This means that gasoline can be ignited when it is in the air at levels between 1.4 and 7.6 percent. A concentration of gasoline vapour in air below 1.4 percent is too "lean" to burn. Gasoline vapour levels above 7.6 percent are too "rich" to burn. Flammable limits, like flashpoints however, are intended as guides not as fine lines between safe and unsafe."

"Flammable and combustible liquids themselves do not burn. It is the mixture of their vapours and air that burns. Gasoline, with a flashpoint of -40°C (-40°F), is a flammable liquid. Even at temperatures as low as -40°C (-40°F), it gives off enough vapour to form a burnable mixture in air. Phenol is a combustible liquid. It has a flashpoint of 79°C (175°F), so it must be heated above that temperature before it can be ignited in air."

Google search for "Flammable Limits"

 

[brian]

..... why do they always explode on TV......

 

[Hickey]

..... why do they always explode on TV......

Cuz they are the bad guys. Bad guys = fumes.

 

[bobdog]

Gas and most other combustable materials need oxygen to burn. The atmosphere inside the tank must have a certain percentage of oxygen before anything will burn.

"Above the upper flammable limit (UFL) the mixture of substance and air is too rich in fuel (deficient in oxygen) to burn. This is sometimes called the upper explosive limit (UEL)."

"Below the lower flammable limit (LFL) the mixture of substance and air lacks sufficient fuel (substance) to burn. This is sometimes called the lower explosive limit (LEL)."

Hence; "Any concentration between these limits can ignite or explode -- use extreme caution! Being above the upper limit is not particularly safe, either. If a confined space is above the upper flammable limit and is then ventilated or opened to an air source, the vapor will be diluted and the concentration can drop into the flammable limit range."

"The lower flammable limit or lower explosive limit (LFL or LEL) of gasoline is 1.4 percent; the upper flammable limit or upper explosive limit (UFL or UEL) is 7.6 percent. This means that gasoline can be ignited when it is in the air at levels between 1.4 and 7.6 percent. A concentration of gasoline vapour in air below 1.4 percent is too "lean" to burn. Gasoline vapour levels above 7.6 percent are too "rich" to burn. Flammable limits, like flashpoints however, are intended as guides not as fine lines between safe and unsafe."

"Flammable and combustible liquids themselves do not burn. It is the mixture of their vapours and air that burns. Gasoline, with a flashpoint of -40°C (-40°F), is a flammable liquid. Even at temperatures as low as -40°C (-40°F), it gives off enough vapour to form a burnable mixture in air. Phenol is a combustible liquid. It has a flashpoint of 79°C (175°F), so it must be heated above that temperature before it can be ignited in air."

Google search for "Flammable Limits"

That is interesting but if you think about it it can not be the only reason that intank pumps don't blow up. Tanks do runout of fuel leaving the pump where it is not protected by the high concentration of gasoline and there would be enough vapor to explode if sparked. I am thinking that the pumps are designed not to create sparks at all ander any circumstances. The wiring must be sealed and grounded very well I am thinking.

 

[Hickey]

It's Magic. Can't we just leave it at that?

 

[jamesgeologist]

Going beyond the chemistry of why gas doesn't necessarily explode in the tank, my guess is the pump itself has all of the electrics totally sealed so that none of the gas can come into contact with spark. Interestingly enough, gasoline can generate its own static charge while it moves through the plumbing at a gas station. The action of placing the nozzle on the rim of your gas spout prevents the static charge from building up.

 

[crimsonride]

That is interesting but if you think about it it can not be the only reason that intank pumps don't blow up. Tanks do runout of fuel leaving the pump where it is not protected by the high concentration of gasoline and there would be enough vapor to explode if sparked. I am thinking that the pumps are designed not to create sparks at all ander any circumstances. The wiring must be sealed and grounded very well I am thinking.

Yeah, and so this is what bothers me. Upon inspecting my fuel pump from a 96 XJ, I actually found a part of wire (ground) that was charred a little and the heat shrink that was around it was split. So I think to myslef "How can this be? It's in a tank full of vapors."
Anyway, I've repaired it and now another concern of mine is how safe am I doing an internal pump on a tank not inteded for it. I do have a loose vent that went to my charcol cannister that I need to reroute somewhere.
hmmmmmm.....

 

[jamesgeologist]

I'd say its not the tank design, but the pump design. Make sure the pump is designed for "in tank" use and you should be okay.