Bushwick Posted March 23, 2016 Share Posted March 23, 2016 Trying to make sure I'm not loosing it or forgetting something, but if BOTH connectors are submerged or wet across the top, how does that not cause a short (not a spark short, but like submerging + and - together? Quote Link to comment Share on other sites More sharing options...
Bushwick Posted March 24, 2016 Author Share Posted March 24, 2016 Anyone? I'd like to try and start it. The rubber boot is over the + end, and it's fairly snug, but I'm just wondering if gas seeps into the boot and top of pump is wet, will it short out? Quote Link to comment Share on other sites More sharing options...
987687 Posted March 24, 2016 Share Posted March 24, 2016 Gasoline has a very low dielectric constant, around 2.0. A vacuum is 1.0, and water is around 80, at room temperature. Therefor gasoline conducts so little electricity as to be irrelevant. Fuel pumps are actually cooled by drawing gasoline through the motor, past the commutator, windings, and out the top. So yes, there are open electrical connections in a gas tank, along with the level sending unit etc. 1 Quote Link to comment Share on other sites More sharing options...
Rooster2 Posted March 24, 2016 Share Posted March 24, 2016 I am not an expert in this area, but having changed in tank fuel pumps before, I have not worried about any trouble from sparking. I don't think gasoline conducts electricity like water, and does not create a fire hazard. It is only when gasoline is in a state of a fine mist with plenty of air with oxygen that it becomes combustive and flammable. The electric fuel pump is actually designed to be cooled by the liquid gasoline surrounding it. I am unsure why a rubber boot is used over the + end. Maybe so it cannot short out if it accidentally grounds itself to something. I cannot imagine that the boot is made to be water proof, since I think it is simply a slide in product. Quote Link to comment Share on other sites More sharing options...
Bushwick Posted March 24, 2016 Author Share Posted March 24, 2016 Thanks. Gas tanks are one area every " i " gets dotted and was concerned. Quote Link to comment Share on other sites More sharing options...
kamesama980 Posted March 24, 2016 Share Posted March 24, 2016 Yep, better safe than sorry when messing with gas tanks but nothing to worry about in this case: every fuel pump I've seen leaves the electrical plugs, pins, or studs in contact with fuel. Quote Link to comment Share on other sites More sharing options...
CNY_Dave Posted March 24, 2016 Share Posted March 24, 2016 I'm 100% sure the brushes are sealed from the gas, though. They spark! Quote Link to comment Share on other sites More sharing options...
987687 Posted March 24, 2016 Share Posted March 24, 2016 I'm 100% sure the brushes are sealed from the gas, though. They spark! Pretty sure my GL fuel pump had fuel flowing past the brushes when I took it apart. Quote Link to comment Share on other sites More sharing options...
DaveT Posted March 24, 2016 Share Posted March 24, 2016 In a GL and Loyale pump fuel flows right through brushes and everything. Sparks submerged in fuel don't do anything. You need fuel and air in the proper range of proportions to get anything "exciting" to happen. 1 Quote Link to comment Share on other sites More sharing options...
CNY_Dave Posted March 25, 2016 Share Posted March 25, 2016 Well, when the fuel is low it's not submerged. Sounds risky to me. Might be able to guarantee a low-energy spark when it's new, but I'd hate to be banking on 'will never happen to have any air in the tank'. Quote Link to comment Share on other sites More sharing options...
CNY_Dave Posted March 25, 2016 Share Posted March 25, 2016 Well, looks like that's what we all are indeed doing, obviously sparking a mixture in a tank is a low-probability event, but not forbidden in any way by physics or thermodynamics. So if you took a tank off, drained it, left it out so it was mostly dried, put it back on, then cranked it before remembering it had no fricken' gas in the tank, you could have an ignitable mixture and a dry sparking pump, so there must be some other mechanism that helps prevent this. Maybe the volume around the brushes is small and any flame gets quenched before it leaves the pump... Quote Link to comment Share on other sites More sharing options...
DaveT Posted March 26, 2016 Share Posted March 26, 2016 Yes, there is that, it is not a big volume in the motor area. I have one around here that I disassembled. The next time I come across it, I have to try powering it up. I suspect that it is likely not run at the extreme power levels that many brush motors you typically see sparking are run at. Since it is meant to run in lube [fuel] the brush material is likely different. I think I remember a metal screen on the inlet, which could possibly serve as a flame stop in the unlikely event of a spark / flash. The shear number of cars running fuel pumps this way - and the never heard of it happening numbers of explosions says something. Quote Link to comment Share on other sites More sharing options...
Macca 351 Posted March 26, 2016 Share Posted March 26, 2016 I worked in a refinery and we had an LPG pipe burst. The only reason there was no explosion was because you need to have the right % off gas and oxygen to be combustible and gasoline as you Americans call it works in the same way. A fumed gas tank would have little to none oxygen hence making it safe Quote Link to comment Share on other sites More sharing options...
kamesama980 Posted March 28, 2016 Share Posted March 28, 2016 Well, when the fuel is low it's not submerged. Sounds risky to me. Might be able to guarantee a low-energy spark when it's new, but I'd hate to be banking on 'will never happen to have any air in the tank'. Well, we've been using electric fuel pumps mostly the same way for a few decades now without much trouble, so yea... Nothing like millions of people driving around with tanks of highly flammable fuel strapped to the bottom of the car. Or in the case of us motorcyclists, between our knees. Quote Link to comment Share on other sites More sharing options...
Bushwick Posted March 28, 2016 Author Share Posted March 28, 2016 I was mainly concerned about both posts being in the gas at the same time, or if gas splashed and created an electrical bridging. They bothered installing the rubber boot over the 12v+ post (and while I was able to reuse it and it was snug, it wasn't air tight) so was just wanting to be 100% certain everything was OK as this was only the 2nd fuel pump I've ever changed in 21 years of car ownership. Quote Link to comment Share on other sites More sharing options...
DaveT Posted March 29, 2016 Share Posted March 29, 2016 Gas and common oils / fuels are non conductive. Quote Link to comment Share on other sites More sharing options...
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