15 yr old son ask me a question I cant answer
 

When working on my 69 and trying to figure out the fuel delivery system, we was working on an idea for an in tank fuel pump. My son said, "let me get this straight, we're goin to run a hot wire down inside a gas tank and it wont blow up?" I said, son all of the newer vehicles have in tank pumps and weve changed out several of them over the years. He said, "but why dont it blow up?" I said, "son I have no idea nor have I ever thought about it." So Im bouncing it off you guys. Help me make sense of his question. I know you guys are goin to think Im crazy for some of the stuff Ive put on here.
Thanks.

Re: 15 yr old son ask me a question I cant answer
 

1) Gotta have oxygen to burn or explode.

2) It's in gasoline, so it can't spark, so it can't start a fire.

3) Gasoline can't burn. Gas vapor burns, but only in the correct air/fuel ratio.

Re: 15 yr old son ask me a question I cant answer
 

also the fuel pump is insulated so the electricity doesn't flow through the gasoline.

Re: 15 yr old son ask me a question I cant answer
 

The fuel pumps are XP rated - XP = explosion Proof
The windings, seals and insulation all play a factor in achiving XP ratings.

Re: 15 yr old son ask me a question I cant answer
 

Pumps are in explosion-proof housings as stated earlier. Also you are probably in the UEL or Upper Explosive Limit, too rich of a mixture for combustion. just like your carb if it is too rich the engine won't fire.

Re: 15 yr old son ask me a question I cant answer
 

I thought would be goin a diff direction......when I was 15 yrs old(about 37 yrs ago), I asked my daddy a ? that he had a time answering! I asked, dad why are women so crazy? after a few stammers, the old man replied"you need to figure out if you need to live with them or not"! Well dad I dont think I can live without them:lol: I know it dont help with an answer......but I hope you see a little humor in it;) those kids will keep you "hoppin"! carazyAL

Re: 15 yr old son ask me a question I cant answer
 

Besides what's already been stated, I'll add that they went to in-tank pumps because they are quieter and because the gasoline acts as a coolant for the pump motor. It's also harder on the pump internals to suck than it is to push - if a rotary pump has to suck a long distance before gasoline reaches it then the pump internals experience faster wear and higher temps before the cooling/lubricating gasoline reaches them.

Re: 15 yr old son ask me a question I cant answer
 

How about an empty (virtually) tank?Your son has an inquiring mind.That`s a great thing.

Re: 15 yr old son ask me a question I cant answer
 

My opinion is A hot wire has no danger or real issue until it is connected, a loose hot wire wont catch a fire. Otherwise a batter would cause a fire just sitting near gas vapors, it has to ground to create a reaction, if groundedsolid and current is running it wont do anything. But if something is faulty and causes a spark and it's near the vapor, kaboooom...

Re: 15 yr old son ask me a question I cant answer
 

Remember TWA Flight 800. Atleast I do, at the time I was living on Long Island, Ny.

Unless you believe it was a missile strike that brought the aircraft down, the other theory is an explosion in a nearly empty fuel tank, the fuel vapors were ignited by an electrical short.

http://en.wikipedia.org/wiki/TWA_Flight_800#Conclusions

Re: 15 yr old son ask me a question I cant answer
 

All of the above is why I prefer placing the fuel tank as far away from the people as possible. There was a test years back that showed a chevy truck flipped on it's drivers side and slidding down the road. The fuel tank cap popped off spilling fuel and the whole thing basically when BOOM!! If you saw the film, you would immediately find a way to get that tank out of the cab!!!!!!!
Pumps push fuel easier then sucking but the primary reason was fuel injection. it requires a lot of pressure and a mechanical pump is not nearly as efficient--it also saps HP. Some vehicles have two push pumps--one in the tank and another prior to the injection. Either can fail and still run.
Quickest way to ruin a in-tank fuel pump is to run the tank dry--pump overheats and dies. Another killer way is to run el-cheapo gas like Marithon---it had some substance that would kill fuel pumps.

Re: 15 yr old son ask me a question I cant answer
 

An explanation of "LEL" and "UEL" (flammability range of gasses in atmosphere)
http://www.mathesontrigas.com/pdfs/p...ve-Limits-.pdf

Under normal conditions, it will be above the UEL. The danger is introduced with the addition of air or oxygen. Well placed electric fuel pumps will be in the base of the tank where vapors collect or submersed in the fuel. Well placed external plugs will be some distance from any openings (fillers or vents). 3 ft is a good margin of safety if the vehicle is worked on outdoors.

Re: 15 yr old son ask me a question I cant answer
 

One theory on flight 800 - the one I like best - is that a high voltage wire running next to a low voltage wire 'leaked' some current into the lower voltage wire. This sparked the vapors in the center wing tank.

So unless GM runs the starter wires with the fuel pump wires through the gas tank, we'll all survive.

That flaming Chevy saddle tank on NBC was proven to be a ratings ploy by the network. They heard Chevy trucks with saddle tanks would blow up when hit on the side. They couldn't get it to work so they rigged a charge up to 'help' their arguement. A laywer with a sharp pencil slowed down the tapes and discovered the charge and made NBC shut up.

Editted by Special-K

Re: 15 yr old son ask me a question I cant answer
 

you bring up a very important subject there. when you replace a fuel pump (in tank) you MUST have fuel in it before turning on the pump. I saw pictures of a shop (at least it used to be a shop) where a tech did it wrong. he turned the key on with an empty tank. the building is gone, tools gone, techs badly burned, customer vehicles destroyed. since that I ALWAYS disconnect the battery until I know for a fact the pump is submerged in fuel.

Re: 15 yr old son ask me a question I cant answer
 

I think the real answer is that the fuel pump is a sealed unit.Much like a submersible sump pump the electrical part of the unit is sealed from the liquid around it.Three phase and single phase pumps run underwater all the time in this configuration.The liquid still cools the unit but doesn't short it out.I don't know but assume that the fuel pumps in modern cars have the equivalent of a GFCI built in to prevent sparking ,thus preventing arcs that start fires.

Re: 15 yr old son ask me a question I cant answer
 

what I thought even more interesting was, I believe, gasoline does not conduct electricity the way water does. I had an instructor in automotive school that used to race electric rc cars and he would wear in his new motors by running them full speed while submerged in gasoline.
the gas would provide just the right lubrication and cooing while still allowing the brushes to "burn in" (bad choice of words) and he would actually get performance increases.

by the way, I've never actually seen this done, so I'M NOT RECOMMENDING ANYTHING, NECESSARILY.

Re: 15 yr old son ask me a question I cant answer
 

You got THAT right.
My Wife learned the Hard way, by overheating the Fuel Pump in her
97 Trans Am.
Take Out the Driveline.
Take Out The Rear End.
Cut The Exhaust
Put everything BACK together.

$900.00 please.............

We now go no lower than a 1/2 Tank on any of our Vehicles.;)

Re: 15 yr old son ask me a question I cant answer
 

Im glad I could start a good topic. Its funny Ive changed a "boat-load" of in tank fuel pumps and never thought about how these thing work. I have to admit it does sound kinda funny, hot wire in gas tank.

Re: 15 yr old son ask me a question I cant answer
 

this is THE answer the 15YO boy needs to hear.

BTW guys, the pumps are not sealed at all.

Re: 15 yr old son ask me a question I cant answer
 

they are not sealed, but you will have a very hard time getting an explosive mixture of air and gas to the brushes. the gas tank will generally be at or above the upper explosive limit as far as the "mixture" inside the tank. the vapor is what burns not the liquid.you have to have an ignition point that is of sufficient temperature to ignite the fumes. I have personally seen cigarette butts thrown into drainbuckets that have contained many a flammable mixture in them. nothing thankfully has happened, it comes down to Flash point, and mixture percentage. but introduce a spark or flame,poof.

Disclaimer: Do not try extinguishing cigarettes in buckets of gasoline or paint thinner. Be a little smarter. Unless your gene pool is that murky, if you do then do not blame me

Re: 15 yr old son ask me a question I cant answer
 

I thought "Jap" was considered a bad word nowadays. I'm not Japanese but could see a person of Japanese descent being offended.

Re: 15 yr old son ask me a question I cant answer
 

It's a politically correct world we live in.:banghead: :lol: JOHN (NOW....BACK TO FUEL PUMPS)

Re: 15 yr old son ask me a question I cant answer
 

Thread corrected in a non-political way.Please stay on topic and leave these judgements to staff.Thank you,Special-K

Re: 15 yr old son ask me a question I cant answer
 

NOW back to fuel pumps!! ;)

Re: 15 yr old son ask me a question I cant answer
 

Edited by staff:
You`re alright.I just edited the crap that started this hijack causing counter comments.:cool: