During the time my Corolla was forced off the road, I would still idle the engine every once in a while to keep everything lubed and working. Over many months, eventually the tank would run low on gas, and I’d have to get some more using my truck and a gas-can. One day while idling the engine I noticed the gas tank was really low, so I poured in some more gas from the can while the engine was still idling. Clouds of black smoke immediately came out the tailpipe. In normal operation there are no such clouds of black smoke out the tailpipe, ever. Any ideas why this black smoke appeared? Does this point to some as yet unnoticed problem? Or is this a normal thing when adding gas to the tank while the engine is idling?
I have no idea. I’ve been taught never to add fuel to a running engine. I never do this although I have never had a good explanation why not. One guy just laughed at me when I gave the reason my dad gave me but then failed to supply his more enlightened reason.
Adding gas to a hot lawn mower engine I understand, especially if you spill it, but the real answer for cars remains elusive. Not a mechanic or engineer.
I assume the Corolla has an evaporative control system of some sort. You may have forced liquid gas into the system, and had that gas end up in the intake. Could be a reason not to fuel a running car.
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I was thinking the same thing. I wonder if it might be an indication the evap canister needs to be replaced? Or maybe the canister is ok, but it was full b/c the engine was mostly not run at all, allowing gas fumes from the tank to eventually saturate the canister, then when running, it was only idling, and therefore not sucking enough of the gas out of the canister and into the engine. At this point, a mystery.
Ditto that. (See, a “+1” button would actually be useful - but I also hit “like” of that makes people happy too).
Maybe it was out of gas and the fuel pressure had gone low. Then it suddenly went too rich when you put more gas in. I did this exact thing once and there was no black smoke though, so I doubt it is this. Oxygen sensors correct immediately.
Did the engine speed change or did it misfire at all when this black smoke came out?
The only thing that seems possible is an issue with the EVAP system.
This makes no sense. I have fueled idling cars and motorcycles all my life with zero issues of course.
I don’t understand how it’s possible.
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OBD1 began in 1988.
An 88 Toyota had a carburetor.
Were you trying to fill the gas tank thru the carburetor?
Tester
Not that I noticed
I’ve had the same experience, never noticed anything unusual happen when refilling the tank w/the engine idling, either warm or cold. (Not claiming this practice is safe or something a person should do of course.)
My current theory is the same as Texases speculates above, the added fuel is pushing gas fumes from the tank into the evap canister, & from there into engine via the purge valve. This wouldn’t happen if the canister were able to capture all the fumes being pushed into it, suggesting the canister is already fully loaded with gasoline or defective. It also wouldn’t happen if the purge valve is always closed during refueling as is the case w/most OBD II engines, but OBD I tech wasn’t as sophisticated. The Corolla’s purge valve opens and closes according only to the coolant temperature.
You never add a flammable fluid like gasoline to a running engine, or even while cranking the engine over in the event it backfires. The Backfire would ignite the gasoline in the pouring stream and the gas in the cup or container that you are pouring from and in the excitement of the can catching fire you would probably try to throw it away and splash the gas on to you… End of story and if you survived, that event would be “burned” into you memory…
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Yeah I understand that. Ruined a good rain coat putting the fire out when the carb backfired.
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Patient: It hurts when I do this (raises his arm)
Doctor: Don’t do that.
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