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

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Bill Putney wrote:


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
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wrote:

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.

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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
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Bob wrote:

Heh heh! Reminds me of the time in a presentation to NASA when I got reprimanded for referring to an activation switch on a joystick for a robotic arm to be used on the space shuttle as a "dead man switch" (this was a few months after the Challenger disaster). (After the meeting, I very quietly joked to a co-worker, "Hmmm - maybe I should have called it a "dead *astronaut* switch?", insinuating that the objection was to the use of the politically incorrect word "man" instead of the generic "person" or "astronaut".)
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
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Why do you think I put the quotation marks around the phrase fire-wall? It's not a fire wall. But that is what most will call it, sort of like using the word Kleenex instead of facial tissue.

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That's odd, my Service Manual still refers to it as the 'firewall'.
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PC Medic wrote:

Hi...
If it isn't to be referred to as a firewall anymore; then I doubt it's to prevent my believing that a fire is possible...
Be more inclined to think they don't want me assume that their firewall would necessarily protect me from one.
Take care.
Ken
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Thomas Moats wrote:

Not only that, but in all modern cars with the epa-mandated evap collection system, if there is a leak detected by a loss in tank pressure, an idiot lamp will come on in the dash, letting you know that something is wrong. Same is true if you drive away from the gas station without putting your gas cap on tight... after about 35 miles or so, the ECM will see that as a leak in the system, and an SES lamp will come on.
And you DO get your car checked out when you have an indication that something is wrong... right?
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Ken Weitzel wrote:

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
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Matt Whiting wrote:

Well *sure* you say that *now*. But would you have wanted to be the first engineer in history to propose doing that? 8^)

Can't argue with that.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
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Bill Putney wrote:

Actually, yes, yes I would! I could use the royalty payments on my patent... :-)

Oh, come on, I'm sure you can! :-)
Matt
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Matt Whiting wrote:

That was cold! 8^)
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
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On Fri, 29 Oct 2004, Bill Putney wrote:

I'd have no qualms being that engineer, and here's why: Gasoline is combustible in only a narrow ratio range with air. Bored suburban kids used to get empty paint cans from the hardware store, put a barbecue sparker with long leads in the side of the can, use an eyedropper to put two drops of gasoline in the can, hammer on the lid, stretch the sparker leads and hit the button to cause a loud noise and a flying can lid.
One drop of gasoline didn't work. Three or more didn't work. TWO drops -- and only two drops -- worked.
The ratio of fuel to air is always much too high (or, if you prefer, the ratio of air to fuel is always much too low) for these hallucinatory panoramas of firy death some people (even engineers, amazingly enough) have been talking about in this thread. That's why they don't happen.
DS
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Daniel J. Stern wrote:

Were you by chance a bored suburban kid, or were you the kid behind the counter at the hardware store (or both)?

Ouch!!
Forget for the moment that you are technically right. You think you could convince the management, lawyers, insurance companies, and stock holders that, statistically over the lifetime of 20 million vehicles, the perfect conditions resulting in huge publicity and multi-million dollar lawsuits would never be met - not even one time? You know - seriously - taking your paint cans and eyedroppers into the conference room just might do it.
Reminds of the engineer that told me I was over-reacting when I went ballistic when a 3 foot long flame shot out of a known leaking hydrogen fitting due to a welder welding above it and showering down sparks - oh - he had draped the hydorgen equipment with a canvas tarp before he started "to be safe". He was telling me that the conditions for hydrogen exploding were so specific that the chances of it happening were extremely small. The funny thing is that hydrogen in a process oven not 10 feet from that very spot where the flame shot out had exploded, blowing the door off of the oven so hard that it moved a 40 ton press a few inches when it struck it. Fortunately, no one was standing in front of the door at the time. Here's the kicker: That incident happened - not *AFTER* the 3 foot flame incident, but 3 years *BEFORE* that - and he still told me I was over-reacting - that an explosion could never happen.
Saying "Oh - that could never happen - let's go ahead and do it" is how you end up on the 6 o'clock news. 8^)
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
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Matt Whiting wrote:

Well, nearly every occurrence of an airbag deployment that I've heard of is unintended... most people, unless they intend to commit suicide or ditch a car and fraudulently claim insurance, do not intend to crash and trigger the airbags. :)
However, there have been a couple of *unwarranted* airbag deployments that I've heard of.
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Isaiah Beard wrote:

Jes make sure you've *always* got them hands at 9 and 3 o'clock in case it does go off. 8^)
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
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Ken Weitzel wrote:

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')
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I may have missed it earlier, but it is your opinion that money had a lot / a little / nothing to do with the design?
Cost of repair was not a consideration?

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Al Smith wrote:

A lot. What else is there (in modern business thinking)?

Having worked in the industry for 7 years, I believe that the primary driver for designs is intial cost to the mfgr., whether in the form of parts cost or assembly labor. *IF* it can be determined that making repairs easier and cheaper will help the mfgr.'s bottom line (i.e., if the buying public becomes painfully aware of the extra cost of ownership due to a poor design), then that may influence the design. In MBA-think, if it hurts the customer or costs the customer money, but the customer never recognizes that to the point of affecting buying decisions, then there is no value added in making the design better. No matter how it's sugar coated, in reality, the term "value-added" means "it improves our profits". IOW, if it is an improvement (for the consumer), but doesn't ultimately help the bottom line, then it isn't "value added" (in MBA-think).
Possibly if it is considered to be a high rate of warranty repair item, then that might be factored in too. But I believe in this case, the prime motivator was total initial cost to the mfgr. IMO...
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
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Bill Putney wrote:

Hi Bill...
I'd have to be several kinds of fool to debate you given your experience. :)
Perhaps though, we should together design a new system? I'm thinking of gravity... :)
Ken
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