Re: In-the-tank fuel pumps cause death and destruction

There's one NUT right here in this newsgroup, Why, it's YOU Nomen!!!!

Senator John Edwards, is that you?

Two examples, of how NOT to properly handle volatile fuels, deleted for lack of relevance. LOL

mike hunt

Nomen Nescio wrote:

in-tank-fuel

Perhaps if your degree was in electrical, rather than mechanical, engineering you might. One reason is liquids can not burn. By being inside the tank, there is no possibility of a combustible mixture or fire. If for example the electric fuel pump were outside the tank, in the line, there is a much greater probability of a combustible mixture occurring in the event of a fuel leak. OK?

mike hunt

Al Smith wrote:

And like any competent mechanic you disconnected the battery first, right? ;)

mike hunt

Alex Rodriguez wrote:

Hi...

I'm electrical - but sure not interested in taking sides in this conversation.

I do have one question though that I'd like to ask if I may? When I have a quarter tank of fuel left, what exactly occupies the remaining space?

Ken

My goodness! You are so full of shit!

Ian

If I see where you're going with this, the inside of the fuel pump (where all the electrical commutation/sparking takes place) is 100% full of liquid fuel under all conditions. Missing only one ingredient for fire or explosion: air/oxygen. Comforting thought, eh?

To answer your question: air (but all the arcing and sparking is inside the pump with only liquid fuel).

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Fuel vapor No oxygen and under slight pressure which keeps oxygen from getting in, or shall I say not enough to support any type of combustion. No degree needed for that.

Gasoline vapor, but not a combustible mixture. Even when the gauge shows empty, the contacts are still in the fuel.

mike hunt

Ken Weitzel wrote:

Hi...

Or maybe one is :)

See if I follow.... they make a mediocre attempt at creating a closed environment. Then we remove some of the contents (burn some of the gas). And end up sith a slight pressure?

Ken

Much more comforting that having the pump outside the tank where all of the ingredients are available. :-)

Matt

Hi Bill...

Sorry I started now. :)

How about at the final few minutes of running out of fuel?

How about turning on the ignition (running the pump for a few secs) when the tank is "empty" ?

How about a flaw in the diptube?

I'm gonna respectfully suggest that were I given a choice; I'd take a pump in the engine compartment (the other side of the firewall being a nice side effect bonus)

Ken

Excess fuel is returned back to the tank. What temperature does gasoline evaporate? Just that question should spark some thought. Now add heated fuel, heated by compression and being near a heat source ( engine ), that statement should provoke some thought as well. Take some gasoline, put it in a closed non-vented container and shake it, then open the lid, notice there is now pressure in the container? Try to draw liquid out of a sealed container, what happens? It collapses. So the tank is designed to hold a small amount of pressure made by the fuel vapors. This is a DOT requirement. There are two valves on a tank. One is in the fuel cap the other is the tank vent. This provides a sealed tank that holds a slight pressure of no more than 2.1 psi over atmospheric pressure.

No O2, no burn.

Still no O2.

dibtube? Do you mean the fill neck? Hole in the fuel tank system can be dangerous, but you need to look at basic laws of physics, you may not be so worried.

The same sheet-metal that makes the "fire-wall" also separates you from the fuel tank.

How many cars have you heard of that have exploded or caught fire from an in-tank fuel pump? In my case, the answer is zero so I don't lose much sleep over it.

I'm more worried about an inadvertant air bag deployment than I am about my gas tank exploding. The former is much more likely than that latter and I've heard of several occurrences of unintended airbag deployment.

Matt

Due to the lawyers I don't believe we have firewalls any more...... that would insinuate that a fire is possible. They are now called bulkheads. Bob

Pumping section (gerotor, turbine, or roller vane section as the case may be for a given design) of the pump is below the commutation section. Check valve in the fuel line keeping the pump full of fuel after pump is shut off. There will always be a column of liquid fuel above the pump commutation level.

See above.

See above. It may be that no single-point of failure will cause a problem. But, as with any system, you can hypothesize a **combination** of failures that would creat a problem (cutting the odds) - you'd have to argue whether or not such a combination of failures was credible. And statistically, those combinations *will* happen. Don't ask me why there haven't been real "unexplained" explosions.

Too much heat - fire and vapor lock potential in the modern engine compartment.

I hear you though. Do a google search on my name and rec.autos.makers.chrysler and "commutation" and you'll see that I was asking the same questions of Ford and Chrysler engineers when I was an engineering manager for fuel pump products as a supplier - you'd be surprised how many of them never even thought to ask the questions - it's just the way things were done since before they were hired, so they never thought about it.

I often said it to them, and I said it in this ng, that if in-tank fuel pumps had not been invented before now, and I thought of doing it, I, as an engineer, never would have suggested it in today's legal and corporate environment - I would have kept my mouth shut for career protection.

Actually, I seriously doubt that it would be being done now if it had not had several years of being done with no indication that it was a real problem. IOW - you could never prove, in theory, to a committe of lawyers, managers, insurers, and MBA's that there could never be a scenario that an explosion could not occur from some credible combination of (1) running the tank out of fuel and (2) a bad in-line check valve in the lines (allowing the liquid to drain back), and (3) someone turning the ignition key to "run" and the fuel pump running dry inside. Oh there will always be those who will have some explanation of why it could never really explode - but wipe out their knowledge that it has ever been done before and put them in the parallel universe where it has not been done before and ask them to be the first person to volunteer to sit in the first vehicle in which it was ever to be tried the first time it was cranked up, and see if they will do it. Everyone has great hindsight knowing that it is in reality apparently safe. But to know ahead of time for sure...?

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')