Cars, gastank, fuel pump, I have a question

[Erkan]

Yo,

my old man is changing the fuel pump in his Audi, and as in all "newer" cars (this one's from -89), the fuel pump is located inside the fueltank and it is electric.

What I wonder is, how did the car companies come to the conclusion that it is safe to put an electric device inside pure gasoline? The cables from the car battery lit a spark on the fuel pump when my old man tested to see if it still works, and it bursted into flames immediately. The pump was taken out of the tank though, so nothing REALLY bad happened The old man is good with mechanical and electronical stuff though so he knows what he is doing, but I am asking this out of pure curiosity.

Anyone knows how this system works and is safe? The pump's cables and stuff aren't even isolated from the gasoline... the whole shit is drenched in it. It feels so wrong

 

[J.DavisNJ]

Wow...that sounds pretty ridiculous to me! Not like it's a Yugo or something either (sorry to any Yugo owners...teehee).

I really can't think of any sensible reason why it would be located there.

-Joe

 

[kev]

Get Gleneth in here He's a mechanic!

 

[Eddy]

I'd guess it's all about the ratio of air to fuel in the tank. Gasoline doesn't burn in liquid state, it has to evaporate into gas and mix with enough air to ignite. Or something like that. It's been a while since my last physics class.

 

[Metaltastic]

Yup, that's true, it's only the vapors of gas that burn, not the liquid. Still, it seems pretty ridiculous, but I guess if it were that dangerous we'd hear about a lot more cars with fires erupting in their gas tanks!

 

[Nebulous]

Yep, no combustion without oxygen. Hence why your car won't run when the air/ fuel ratio is too stuffed. Even with the ingnition system delivering live elecrtricity the fuel won't ignite without the presence of enough oxygen.
Also, having the pump located in the fuel tank is good for two reasons:
- It's more "inline" with the tank (as opose to sitting above the tank), so it's doing less work against gravity, which reduces wear and tear on it
- Unless the tank is ruptured, it can't explode or be interfered with by anything external.

 

[Erkan]

Oh, good points dudes! Thanks for the reply, it makes sense.

For what it's worth, he fixed the pump... damn old man, he fixes anything that is broken

 

[Atheist]

Wow...that sounds pretty ridiculous to me! Not like it's a Yugo or something either (sorry to any Yugo owners...teehee).

I really can't think of any sensible reason why it would be located there.

-Joe

Being the proud citizen of the contry that produces Yugo's I have to say that I wouldn't be surprised if they put a spare spark plug in the gas tank.

There's a story circulating here: A man bought a brand new Yugo and discovered that the cover on one door was loose. So he removed the cover to see what's the problem and found a note: "Salary sucks - door sucks".

 

[Erkan]

So he removed the cover to see what's the problem and found a note: "Salary sucks - door sucks".

HAAAAAAAAAAAHAHAHAHAHA THAT IS HILARIOUS!!

Oh my freakin' god, if I found a note like that in something I bought, I would roll on the floor laughing until I couldn't breathe anymore.

Hahaha... it's so fucking awesome, right on spot! Very descriptive while using very few words... man it's fucking genious "Salary sucks - door sucks" haha.

 

[slashvanyoung]

It's an Audi dude! Of course there is a perfectly sound reason for it, being the single GREATEST of all car makers ever in existence!11

Which one is it? Being born around 89, it's probably a 80/90/100... or V8.

 

[Erkan]

It's an Audi dude! Of course there is a perfectly sound reason for it, being the single GREATEST of all car makers ever in existence!11

Which one is it? Being born around 89, it's probably a 80/90/100... or V8.

Audi 100 2.3E I think



I saw the cables are connected to the pump from the top of the pump, which means if you're low on gas, the cables will be exposed to gasoline fume instead of being drenched in gasoline. Is there still no risk of explosion if a spark would somehow erupt from the cables? Maybe there isn't much room for oxygen in the gas tank with all the fume and shit.

 

[Nebulous]

Not enough oxygen, too much pressure from the fumes to get the oxygen to the wires. I'm pretty sure that oxygen is a lighter gas than the fumes/ petrol vapours, so the oxygen would probably be sitting at the top of the tank away from the wires.

Honestly, that design has been around for long enough now that it's not something to be worried about unless you start to see wear and tear on either the pump or tank to suggest that more oxygen is getting into it that is normal.

 

[Erkan]

Aye, thanks for the reply Nebulous.

Well, my curiosity taught me something very interesting! I had no clue gasoline fumes were not igniteable without oxygen. I thought it could ignite pretty much anywhere.

The car is fixed now and runs smoothly.. I should get my driver's license before I turn 23, so it's time to practise on this car before something else breaks down again, haha. It is a very interesting car, something semi-major breaks down every couple of months, which results in me learning tons of shit from dad when he fixes it. Even he learns new stuff as we go. Hell, the car's major parts should be brand new soon if this continues like this... everything is getting replaced

 

[Via Noctis]

Nothing burns without oxygen.

 

[Erkan]

Nothing burns without oxygen.

Yeah, I know that but for some reason, I thought gasoline fumes were highly explosive. So basically, in a room full of gasoline fumes but no oxygen, if you lit a torch, it wouldn't explode huh? Quite amazing