Diesel Refueling Explosions

[dsmith41]

Most every gas station has the disclaimer at the pump that tells you to turn off your engine before refueling because it can supposedly cause an explosion. My question is concerning diesel fuel; why do I see diesel trucks at the pump running their engines while they refuel with seemingly no worries or problems? Is it because diesel fuel is not as volatile? Trying to rationalize this in my head, I was thinking that diesel engines do not have spark plugs, and therefore less risk of explosion. But then I was thinking the spark from the combustion chamber of a gasoline engine should be well sealed from the outside air so maybe that doesn't even make a difference.

Can someone provide me with a scientific explanation to shed light on this for me? Its just my curious mind here wanting to know. Is it even necessary to shut off a gasoline engine at the pump or is it just that the gas station's lawyers want that disclaimer on all the pumps?

 

[Drew99GT]

I think the explosion potential comes more from static electricity on your person and the outside of a vehicle. That's why they say to ground yourself before fueling, especially if fueling a small container of fuel such as for lawn equipment. Which begs the question - why the need to turn the engine off? I guess if there is an explosion and the engine is running, so is the fuel pump and there could be more potential fuel to burn.

Truckers keep their engines running 24/7 it seems. Don't want the cab to get too cool in the winter or too hit in the summer, and it can take like 10/20 minutes to fuel a big rig.

And you're right; gasoline is more volatile then diesel, and will vaporize much much faster. The vapors are the likely source of ignition.

 

[UG_Passat]

Diesel isn't quite as volatile as gasoline.

But really, the loss of fuel pressure of the gas cap will trigger a CEL on gasoline engines.

ON diesels, AFAIK, (at least my old TDI), the tank is vented when you screw in the cap--- so it's not an emissions systems concern.

The danger is static discharge, but again that's more of a gasoline thing.

 

[dsmith41]

Okay, that is kind of what I was thinking. My pickup is gasoline powered but when I refuel in the winter, I like to just keep the engine running so it is still nice and toasty when I get back in. Granted, it doesn't take me 20 minutes to fill up but still. And from an oil standpoint, I figure it is better to keep it warm and flowing rather than let it cool and start the truck up again.

 

[simple_gifts]

Quote:

Okay, that is kind of what I was thinking. My pickup is gasoline powered but when I refuel in the winter, I like to just keep the engine running so it is still nice and toasty when I get back in. Granted, it doesn't take me 20 minutes to fill up but still. And from an oil standpoint, I figure it is better to keep it warm and flowing rather than let it cool and start the truck up again.

I'm totally curious how you came to this conclusion (that it is ok) from the comments above.

Quote:

Most every gas station has the disclaimer at the pump that tells you to turn off your engine before refueling because it can supposedly cause an explosion.


Most of this is per order of Fire Marshalls etc. Less "stuff" can happen with the auto shut off. A nice gas spill under an idling cat isn't what you want. For the sake of others around you, play it safe.

 

[MONKEYMAN]

I kinda shook my head when I filled up gas a few days ago. A man at the pump behind me did the following: kept the car running, was smoking while pumping the gas, then spent an extra 20 seconds or so clicking the pump on when topping it off.

 

[ekpolk]

Originally Posted By: MONKEYMAN
I kinda shook my head when I filled up gas a few days ago. A man at the pump behind me did the following: kept the car running, was smoking while pumping the gas, then spent an extra 20 seconds or so clicking the pump on when topping it off.

Gee, the only thing he left out was a cell phone call. . .

 

[ionbeam22]

I always turn off the engine when refueling, since in general there isn't a single good thing that can happen between a running engine and any stray flammable vapors.