I think I have asked this in another thread, but I didn't get a response. I may be overlooking something very simple, but whether I am or not, I won't feel comfortable converting to E85 until I understand the answer.

E85 is electrically conductive. Gasoline is not. Our cars, like most, have in-tank fuel pumps. The positive and negative connection to the pump is on the top of the pump.

So, my question is: What is keeping our pumps from shorting out and blowing a fuse in E-85?

I know that GM uses special electrically shielded fuel pumps for their flex-fuel vehicles, but I haven't had a chance to actually see this pump in person. I know that many people are using E85 in their Evos with 0 issues, so I know this is a non-issue. But, what am I overlooking here?

I understand that explosion potential shouldn't be a factor because of the LEL and HEL of E85 and not enough oxygen being in the tank, but I still don't quite understand why the positive wire wouldn't short out when submerged in electrically conductive E85.

Does our pump sit high enough where the top connector isn't submerged, even when the tank is full? I didn't think so, but maybe. If it were high enough, woudln't there still be a shorting potential with the movement of the gasoline in the tank?

Hopefully, someone can point out the obvious to me and make me feel dumb. In the meantime, thanks for reading.


Eric

 

I would think the grounding and fuel stabilizers have something to do with it.
We just use grounding, bonding, and ventilation at work.

 

Hmm i bet Ted B would have a answer for ya Send him a pm

 

I don't believe ethanol is conductive enough to create an issue, unless of course it's contaminated with dissolved metals, water, etc. If one digs deep into the matter, he'll likely find a conductivity limit used as a QA/QC measure for E85 and other ethanol-containing fuels.

 

I think I actually came across this information at one point in my research, I'll see if I can find the actual information that I had found before commenting.

 

Has anyone found any additional information on this? It seems like my searching is falling short.


Eric

 

I haven't found much useful information, I thought I did at one point but never found it. There are enough E85 conversions right now that we should start hearing about problems in the next few months. I had been debating which way to go with the fuel pump, I like the dual in-tank pumps, but I'm not too keen on the methods of controlling it. So I'm probably going to stick with a high volume external pump.

 

That's the route I was thinking, too. But searching for fuel pumps and E85 brings back so much other literature that it is difficult to find what I am looking for.

Do you have any external pumps in mind? Are there any pumps that are capable of flowing enough that aren't annoyingly loud?


Eric

 

The answer is pretty easy.

Even though our fuel pump is basically a giant inductor the ground lead connected to the fuel pumps wiring is substantially a BETTER ground than across the liquid.


Here's the facts:

Dielectric Constants
Gasoline 2.2
Ethanol 24
Methanol 33.6
Water 48 - 88

A dielectric material is a substance that is a poor conductor of electricity, but an efficient supporter of electrostatic fields. If the flow of current between opposite electric charge poles is kept to a minimum while the electrostatic lines of flux are not impeded or interrupted, an electrostatic field can store energy. This property is useful in capacitors, especially at radio frequencies. Dielectric materials are also used in the construction of radio-frequency transmission lines.

Its conductivy is measured in mho's which is the inverse of ohm's

Gas: 1.0 x 10^-14 mhos/cm
Ethonal: 1.35 x 10^-9 mhos/cm

To conver this to ohms simply is the inverse

Gas is 1x10^14 ohms/cm
Ethanol is 1.35 x 10 ^ 9 ohms/cm

Yes thats like BILLIONS of ohms per cm, you can see why its not a big issue right?

 

RoadSpike,

Thanks for the data. That definitely helps a lot. It wasthat type of data that I was looking for.

I'm curious as to why the many research papers that I have read regarding converting vehicles to E-85 always mentioned the potential fire hazard of the electrically conductive E-85 when using intank pumps.

Almost every paper that I read always converted to an electrically shielded GM flex-fuel pump or a pump supplied by Delphi that was ethanol compliant. Although, it seemed as though their biggest concerns where the internals of the pump and not the actual wiring connections to the pump.

I actually have a materials engineering degree, not electrical, but that resistance data for E-85 makes it looks like it is basically a non-issue.

Thanks for the data.


Eric

 

Under any reasonable circumstances i can't really find even Pure ethanol being that big of an issue. Likely its just manufacturers doing what they do best and inventing reasons for you to believe stories and "have" to buy new equipment.

 

you'd have to have a ground fault to make something go wrong in the tank... that's possible... guess you could use a ground fault circuit interupter. iunno.

 

True though as pointed out on mythbusters even shooting a gas tank seems unable to produce an explosion. If a direct short did occur its only on a 20-30amp circuit so I have my doubts even a direct spark would ignite the fuel.

Still would be interesting to test

 

well usually what ignites is the vapors. so if there was sloshage you could have some vapors ignite but they'd quickly be quenched cuz the tank is air tight smog system. reminds me of the stupid lady that went to the gas station put on a polyester sweater and then touched the fill handle... saw the flames and then pulled the nozzle out.... no caboom... that's for hollywood.

i have seen a car shot such that it exploded... the fact is that bullets entering a car usually aren't hot enough to ignite fuel or vapor. but tracers rounds are, and when you hit a car with a vulcan canon armed wtih tracers... it'll explode. there's a vid on youtube of this.

 

Awesome I will be checking out that youtube