Petrol leaking into hot engine but no fire

[sagaboy]

Yesterday, my friend drove 30 miles to my place with engine oil temperature at 210F (because he didn't cover up 3 tin holes), when he arrived, I smelled petrol, open the engine bonnet and saw (showed it to him) petrol dripping fast non-stop from the fuel pump input fuel hose (due to no hose fastener/clip) into the hot engine.

Why didn't it catch fire? I told him--petrol + hot engine = explosion/fire--it must be his lucky day!

[SCOTTRODS]

Yesterday, my friend drove 30 miles to my place with engine oil temperature at 210F (because he didn't cover up 3 tin holes), when he arrived, I smelled petrol, open the engine bonnet and saw (showed it to him) petrol dripping fast non-stop from the fuel pump input fuel hose (due to no hose fastener/clip) into the hot engine.

Why didn't it catch fire? I told him--petrol + hot engine = explosion/fire--it must be his lucky day!

Lucky day for sure,...... So what'd you do?

[landrocket]

I wonder if it was dripping down along the tin and out the bottom, beneath the crank pulley? Raw fuel is hard to ignite, but the vapor, KABOOM!!!

[Marc]

...Raw fuel is hard to ignite, but the vapor, KABOOM!!!

Exactly. The fuel/air mixture needs to be correct before it'll ignite. I'm not recommending that you try this, but I can assure you that it's possible to toss lit matches into a bucket of gasoline without lighting it afire IF they manage to make it through the vapor cloud and hit the liquid, where they're extinguished just as nicely as they'd be in water.
Consider this - almost every car on the road has an electric fuel level sender, and most made in the last few decades also have an electric fuel pump inside the tank. Plenty of potential for arcing & sparking inside the tank, but does anyone lay awake at night worrying about it causing an explosion?

http://en.wikipedia.org/wiki/Flammability_limit

[misterman]

Yep as marc said. Fuel (petrol) is picky. It wants proper fuel to air ration and presers to ignite in HEAT, PRESSURE and as a VAPOR.

U saw the fuel boil and evaporate. I have seen it sever times on dirtbikes. Dont worry, in class we boiled ethanol and alchol. With no explosions.

I recomend always carrying a CHEMICAL type fire extinguisher. Ive have 2 cars catch on fire in 5 years.

[Piledriver]

I also strognly recommend always using hose clamps
EFI type preferably...
They cost the same for same quality, and the EFI clamps don't chew up the hose.

Also don't forget that fuel lines never age well.

[landrocket]

Ditto, keep a CHARGED fire ext. in your ride. Sinking feeling watching your car burn to the ground, when all you had to do was give it a quick blast and put the fire out, but when you pulled the pin and hit the trigger, nothing happens, check it regularly. Been there, done that, and have a torched t-shirt to prove it.

[sagaboy]

I wonder if it was dripping down along the tin and out the bottom, beneath the crank pulley? Raw fuel is hard to ignite,...

Yes, exactly.

[Sneaks]

Consider this - almost every car on the road has an electric fuel level sender, and most made in the last few decades also have an electric fuel pump inside the tank. Plenty of potential for arcing & sparking inside the tank, but does anyone lay awake at night worrying about it causing an explosion?

http://en.wikipedia.org/wiki/Flammability_limit

Actually had this situation on the wife's car (Ford). Fuel pump started working erratically one August afternoon (mid-80s F temps). Parked it, took out the rear seat, cut a hole in the floor pan and pulled the pump. The ground on the pump broke and was making intermittent connection - probably depending on road smoothness, pump torque, etc. I can't see how there wasn't some sort of arc as the ends were blackened but fortunately, no fireball.

[misterman]

Consider this - almost every car on the road has an electric fuel level sender, and most made in the last few decades also have an electric fuel pump inside the tank. Plenty of potential for arcing & sparking inside the tank, but does anyone lay awake at night worrying about it causing an explosion?

http://en.wikipedia.org/wiki/Flammability_limit

Actually had this situation on the wife's car (Ford). Fuel pump started working erratically one August afternoon (mid-80s F temps). Parked it, took out the rear seat, cut a hole in the floor pan and pulled the pump. The ground on the pump broke and was making intermittent connection - probably depending on road smoothness, pump torque, etc. I can't see how there wasn't some sort of arc as the ends were blackened but fortunately, no fireball.

Woah. Thats always been my biggest fear.

In tank pumps still make me go...hummmm haha

[Piledriver]

Fortunately the fuel vapor displaces most of the air, so no kaboom today.
Perhaps kaboom tomorrow, but no kaboom today.

[crvc]

Years ago I had a 1971 914. I had just filled the gas tank. I was told the fuel line is on the left side so I was using oxy/acetylene to braze rust holes on the right side. I heard bubbling sounds but didn't think much about it at first. But then I must have burned through the fuel line and suddenly the entire front was engulfed in smoke. I pushed the car out of the garage and screamed for my wife to bring a hose. I had a hose already connected and started spraying everywhere. My wife brought another hose up from the house and started spraying water as well. With the smoke dampened by water I saw flames pouring out under the front of the car passenger side. I laid down in the mud and continued spraying from underneath. Eventually the car ran out of gas and the flames went out. The entire time I was laying there I kept thinking of all the TV shows where everyone goes running because a car on fire ultimately explodes. Why didn't the car explode and kill us both? I assume the gas was burning fast enough that fumes didn't collect?

On the positive side, the fire burned off most of the paint up front and exposed a lot of bondo and rust I didn't know was there.

kevin

[Sneaks]

In order for an explosion to happen, you need not only ignition but pressure. Fuel dropping out of a fuel line at gravity has no pressure. Put fuel vapor in a confined area and you could have a 'boom'. Likewise if you ignite a large quantity of vapor you will get a fast-moving fire that will flash and 'whoosh', but even then, it sounds like neither situation was present in your case. Don't confuse stunts on TV with reality. Mythbusters tried to get a gas tank to explode 300 different ways from Thursday and still didn't go.

Glad everyone was ok. This is why I always have an ABC fire extinguisher handy at all times when working on a car, and if I'm welding, I have either the son or the wife standing by with it in their hands, pin out and ready to go.

[Jim Ed]

Yesterday, my friend drove 30 miles to my place with engine oil temperature at 210F (because he didn't cover up 3 tin holes),

It should have the 2 fresh air hoses connected from the fan shroud to the heater boxes.

The heater boxes are supposed to have air going through them.
If they don't they will get too hot and help heat the engine.
Even with the heater box flaps closed, some air still goes through them.